EMBRYOGENESIS
Important Events and Their Time Sequence: (Days)
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Common Signaling Pathways Used during Development
The differentiation of many different cell types is regulated through a relatively restricted set of molecular signaling pathways:
- Morphogens: These are diffusible molecules that specify which cell type will be generated at a specific anatomic location and direct the migration of cells and their processes to their final destination
- These Include
- Retinoic acid
- Transforming growth factor bone morphogenetic proteins (BMPs) and
- The hedgehog and the Wnt family proteins
- Notch/Delta: This pathway often specifies which cell fate precursor cells will adopt
- Transcription factors: This set of evolutionarily conserved proteins activates or represses downstream genes that are essential for many different cellular processes. Many transcription factors are members of the homeobox or helix-loop-helix (HLH) families. Their activity can be regulated by all of the other pathways described in this chapter
- Receptor tyrosine kinases (RTKs): Many growth factors signal by binding to and activating membrane-bound RTKs. These kinases are essential for the regulation of cellular proliferation, apoptosis and migration as well as processes such as the growth of new blood vessels and axonal processes in the nervous system.
Fetal Landmarks (Weeks)
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Stem cells must be able to:
- Divide to produce sufficient cells
- Differentiate into the cell types needed
- Survive after transplant
- Mesh into the surrounding tissues
- Function properly for long enough to extend the recipient’s life or to improve it significantly
- Avoid harming the recipient
Karyotyping
In 1961 an international meeting was held at the University of Colorado Medical School in Denver, Colorado to standardize the format for a normal human karyotype. The format that evolved is known as the ‘Denver System.’
Each chromosome has its own individuality as shown by its size, shape, and position of its kinetochore. Using the ‘Denver System,’ the chromosomes are put into similar groups designated by letters. Then numbers are used to subdivide the chromosomes within the groups designated by numbers based on the position of the kinetochore and the length of the chromatids. The homologous chromosomes are paired based on their banding.
X Chromosome belongs to group C
Y Chromosome belongs to group G
Group A | Ch 1, 2, 3 |
Group B | Ch 4, 5 |
Group C | Ch 6, 7, 8, 9, 10, 11, 12, X |
Group D | Ch 13, 14, 15 |
Group E | Ch 16, 17, 18 |
Group F | Ch 19, 20 |
Group G | Ch 21, 22, Y |
Important Embryological Structures: High Yield Points for USMLE
Meckel’s Diverticulum
This true diverticulum is a remnant of the vitelline duct and often contains ectopic gastric mucosa which can cause bleeding and perforation.
The Ductus Venosus
It is a shunt that bypasses the liver and carries blood from the umbilical vein directly to the IVC. Its remnant is the ligamentum venosum.
The Ductus Arteriosus
It is a shunt that bypasses the lungs to carry blood from the pulmonary artery to the aortic arch. Its remnant is the ligamentum arteriosum.
The Urachus
- Becomes the Median umbilical ligament
- The 2 umbilical arteries becomes the Medial umbilical ligaments
- Urachal fistula from persistent allantois
The Vitelline Duct
- It is a connection with the yolk stalk and bowel, but normally obliterates during week 7 of development.
Fetal Structure | Adult Remnant |
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- Connects fetus and placenta
- It is rich in Wharton’s jelly
- Has Two arteries and one vein
- Rt umbilical vein disappears, left is left
- In case of single artery only, congenital anomalies should be excluded
- Umbilical arteries carry deoxygenated blood
- Umbilical arteries do not possess internal elastic lamina
- Vas vasorum are absent in cases of umbilical vessels
Female Gametogenesis
- Oogonia are derived from yolk sac
- Germ cells are derived from yolk sac
- Polar bodies are formed during oogenesis
- Polar bodies are extruded 24 hours prior to ovulation
Male Gametogenesis
- Spermatogenesis occurs at temperature lower than body temperature
- Y chromosome is ACROCENTRIC
- In absence of Y chromosome ovaries develop
- Sperms are stored in epididymis
- Length of mature human sperm is 50–60 microns
Chromosomal Configuration of Important Cells in Gonads
Number of Chromosomes in Cells During Gametogenesis | |
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Placentation: (USMLE Favorite)
Abnormalities of Placenta
- Biscoidal placenta: Placenta has two disks
- Lobed placenta: Placenta divides into lobes
- Diffuse placenta: Chorionic villi persist all around the blastocys.
- Placenta succenturiate: Small part of placenta separated from the rest
- Circumvallate: Edge of placenta covered by circular fold of deciduous
According to umbilical cord attachment:
- Marginal: Marginal as well as battledore placenta refers to placenta with cord attached to margins
- Furcate: Blood vessels divide before reaching the placenta
- Velemantous insertion: Blood vessels are attached to amnion where they ramify before reaching the placenta
- Oligohydramnios: Low level of amniotic fluid (< 400 ml) in renal agenesis
- Polyhydramnios: High level of amniotic fluid (>2000 ml)
- In the fourth intrauterine month the fetus begins to swallow amniotic fluid (25 to 40% of the volume) and absorbs the fluid from the upper gastrointestinal tract
- The fluid is urinated back out into the amniotic pool by the fetal kidneys and a functioning bladder. Although there are maternal causes of polyhydramnios (cardiac failure, renal failure, other causes of fluid retention) and some idiopathic cases, many instances are related to the presence of fetal anomalies. These include:
- Central nervous system problems such as anencephaly, which prevents normal swallowing, and any high alimentary tract obstruction that blocks the passage of the amniotic fluid and prevents its absorption such as:
- Esophageal atresia
- Pyloric atresia
- Duodenal atresia
- Maternal diabetes
- Amniotic band syndrome: When bands of amniotic membrane encircle and constrict parts of fetus causing limb amputations and Craniofacial anomalies
USMLE Case Scenario
Polyhydramnios is not seen in one of the following conditions:
- Esophageal atresia
- Duodenal atresia
- Pyloric atresia
- Hirschsprung’s disease
- Congenital diaphragmatic hernia
Ans. 4. Hirschsprung’s disease
Derivatives of Germ Layers: (USMLE Favorite)
Derivatives of Ectoderm
- Skin and most of appendages
- Lens of eye
- Epithelial linning of Lower half of anal canal
- Epithelial lining of external auditory meatus
- Epithelial lining of distal part of male urethra
- Adenohypophysis
Derivatives of Mesoderm
- Musculoskeletal system
- Cardiovascular system
- Kidney, ureter
- Trigone of bladder (mesonephric duct absorption)
- Posterior wall of prostatic part of male urethra
- Reproductive tract except labia majora, minora and major part of prostate
- Mesothelium of pleural, pericardial and peritoneal cavities
- Dentine of teeth
- Cornea, sclera, choroid, ciliary body and iris of eye
- Somites from paraxial mesoderm
Derivatives of Endoderm
- Epithelial lining of GIT
- Epithelial lining of Biliary tract
- Epithelial lining of Respiratory tract
- Epithelial lining of vagina
- Epithelial lining of auditory tube, middle ear
Development of Lungs
| 5–17 weeks | Respiration not possible |
| 16–25 weeks | Respiratory bronchioles and terminal sacs form |
| 24 Weeks–birth | Type I and II Pneumocytes present |
| Birth-8 years | Respiratory bronchioles, terminal sacs, alveolar duct, alveoli↑ |
Embryology of Heart: (USMLE Favorite)
Embryonic Structure | Adult Structure |
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Embryonic Structure | Adult Structure |
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Remember
| Lesser omentum, hepatoduodenal, hepatogastric, falciform, coronary and triangular ligament of liver |
| Greater omentum, mesentry of small intestine, mesoappendix, sigmoid mesocolon, transverse mesocolon |
Embryology of Urinary Tract: (USMLE Favorite)
Embryo | Adult structure |
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Gonads | Ovary | Testis |
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| Appendix vesiculosa Duct of Garnier | Epididymis ductus deferens Seminal vesicles Ejaculatory ducts Appendix epididymis |
| Epoophoron Paroophoron | Efferent ductules Paradidymis |
| Clitoris | Glans penis |
| Labia minora | |
| Labia majora | Scrotum |
USMLE Favorite
Embryonic Structure | Female | Male |
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| Ovary | Testis |
| L majora | Scrotum |
| L minora | Ventral aspect of penis |
| Clitoris | Glans penis |
Testicular Descent
| 3rd month |
| 7th month |
| 7th month |
| 8th month |
| 9th month |
Derivatives of Neural Crest
- Neurons of spinal posterior nerve root ganglia
- Neurons of sensory ganglia
- Neurons of autonomic ganglia (sympathetic ganglia)
- Schwann cells
- Melanocytes
- Piamater and arachnoid matter
- Mesenchyme of dental papillae
- Cartilage cells of branchial arches
- Chromaffin tissue
- Albinism
- Melanoma
- Hirschsprungs disease
- Oropharyngeal teratoma
- Neurocristopathies (Cleft Lip, Cleft palate, Digeorges syndrome, Waarden burgs syndrome, Charge syndrome
Tumors of Neural Crest Origin
- Neuroblastoma
- Pheochromacytoma
- Carcinoid tumor
- Neurofibromatosis
- Medullary carcinoma thyroid
USMLE Case Scenario
A newborn boy does not pass meconium until 45 hours after his birth. Several weeks later his well educated mother complains that he has not been passing stool regularly. Anorectal manometry reveals increased internal anal sphincter pressure on rectal distention with a balloon. The patient’s disorder maybe attributed to distention with a balloon. The patient’s disorder maybe attributed to:
- Defective recanalization of the colon
- Failure of neural crest cells to migrate
- Herniation of abdominal contents into the umbilical cord
- Persistence of the proximal end of the yolk stalk
- Persistence of processus vaginalis
- Failure of gastrulation
Ans. 2. Failure of neural crest cells to migrate
Pharyngeal Apparatus (USMLE Favorite)
- Pharyngeal Arches are derived from Mesoderm
- Pharyngeal clefts are derived from Ectoderm
- Pharyngeal Pouches are derived from Endoderm
- Meckels Cartilage:
- Mandible
- Malleus
- Incus
- Sphenomandibular ligament
- Muscles: Muscles of mastication (Medial pterygoid and lateral pterygoid, masseter, temporalis)
- Two Tensors (Tensor tympani, tensor palati)
- Mylohyoid, anterior belly of digastrics
Pharyngeal Arch 2 Derivatives (Word S)
- Reicherts Cartilage:
- Stapes
- Styloid process
- Smaller cornu of Hyoid Bone
- Superior surface of Hyoid Bone
- Stylohyoid ligament
- Muscles of facial expression, Stapedius, Stylohyoid, Posterior Belly of Digastric
- Platysma
Pharyngeal Arch 3 Derivatives
- Greater cornu of Hyoid Bone
- Stylopharyngeus muscle
Think of Stylopharyngeus when thinking about Glossopharyngeal Nerve
Pharyngeal arch 4 and 6 Derivatives
- Cartilages of larynx
- Intrinsic muscles of larynx and pharynx
PHARYNGEAL ARCH 5 DOES NOT CONTRIBUTE TO DEVELOPMENT
Nerve Supply of Pharyngeal arches is: My Father gave me Some Rupees
- Mandibular nerve Ist arch
- Facial nerve 2nd arch
- Glossopharyngeal nerve 3rd arch
- Superior laryngeal nerve 4th arch
- Reccurent laryngeal nerve 6th arch
Treacher-Collins syndrome/Mandibulofacial dysostosis
- Abnormal formation of pharyngeal arch
- Faulty migration of neural crest cells
- Hypoplasia of the facial bones: An underdeveloped mandibular and zygomatic bone leading to a small and malformed jaw
- Ear anomalies: Consist small, rotated or even absent ears with or without bilateral stenosis or atresia of the external auditory canals
- Eye problems: Varying from colobomata of the lower eyelids and aplasia of lid lashes to short, downslanting palpebral fissures and missing eyelashes. Vision loss can occur and is associated with strabismus, refractive errors, and anisometropia
- Cleft palate
- Airway problems: Which are often results of mandibular hypoplasia
- Dental anomalies: Consist in tooth agenesis, enamel disformaties and malplacement of the maxillary first molars.
Less Frequent Defects
- Nasal deformity
- High-arched palate
- Coloboma of the upper lid
- Ocular hypertelorism
- Choanal atresia
- Macrostomia
- Preauricular hair displacement
Pharyngeal Pouch | Adult Structure |
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Pharyngeal Cleft/Groove | Adult Structure |
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Cleft Lip and Cleft Palate: (USMLE Favorite)
Cleft Lip:
- Failure of Fusion of Maxillary and Medial Nasal Process
- Usually associated with cleft palate. (Commonest)
- Midline cleft lip is due to failure of fusion of two medial nasal processes
- Cleft Palate: Failure of fusion of lateral palatine process, nasal septum and median palatine process (occasional)
Cleft Lip and Cleft Palate (Detailed Overview)
Unilateral cleft lip. Also called Harelip |
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Midline defect of upper lip |
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Midline defect of lower lip |
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Microstomia |
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Macrostomia |
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Oblique facial cleft |
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- 1st pharyngeal arch forms ant 2/3
- 3 rd and 4 th arch forms post 1/3
- Muscles of tongue develop from occipital myotomes
- Muscles of tongue are both smooth and skeletal muscles
- Muscles of tongue are supplied by hypoglossal nerve
- Safety muscle of tongue is genioglossus
- Tip of tongue drains to submental lymph nodes
- Posterior 1/3 of tongue is supplied by glossopharyngeal nerve
- Pain of cancer base of tongue is also reffered to ear through glossopharyngeal nerve
- Circumvallate pappilae of tongue are supplied by glossopharyngeal nerve
- Anterior 2/3 of tongue develops from lingual swellings and tuberculum impar
- Anterior 2/3 of tongue is supplied by chorda tympani (FACIAL) (taste)
- Anterior 2/3 of tongue is supplied by lingual nerve (general)
- Anterior 2/3 of tongue drains into submandibular lymph nodes
- Posterior 1/3 of tongue develops from hypobranchial eminence
- Posterior 1/3 of tongue is supplied by glossopharyngeal nerve (taste)
- Posterior 1/3 of tongue is supplied by glossopharyngeal nerve (general)
- Posterior 1/3 of tongue drains into jugulo omohyoid lymph nodes
- Tip drains into submental lymph nodes
Tonsil: (USMLE Favorite)
- Has nonkeratinized squamous epithelium
- It is an endodermal structure
- Rests on superior constrictor muscle of pharynx
- Vagus supplies tonsil
- Main nerve supply is the glossopharyngeal nerve
- Lymph drains into jugulo digastric nodes
- Arterial supply:
- Ascending palatine
- Descending palatine and
- Ascending pharyngeal artery supply tonsils
Diaphragm Development
- Septum transversum
- Pleuroperitoneal folds
- Body wall
- Dorsal mesentry of esophagus
Development of Intra-abdominal Organs Frequently Asked
Spleen
It is unique in respect to its development within the gut. While most of the gut viscera are endodermally derived (with the exception of the neural-crest derived suprarenal gland), the spleen is derived from mesenchymal tissue. Specifically, the spleen forms within, and from, the dorsal mesentery.
Pancreas
The pancreas develops between the layers of the mesentery from dorsal and ventral pancreatic buds of endodermal cells, which arise from the caudal or dorsal part of the foregut. Most of the pancreas is derived from the dorsal pancreatic bud. The larger dorsal pancreatic bud appears first and develops a slight distance cranial to the ventral bud.
The liver, gallbladder and the biliary duct system arise as a ventral outgrowth (hepatic diverticulum) from the caudal foregut in the 4th week
- This hepatic diverticulum extends into septum transversum, a mass of splanchnic mesoderm between the developing heart and the midgut
- The septum transversum forms the ventral mesentery in this region. This double-layered membrane gives rise to the lesser omentum and the falciform ligament
- The superior layers of the coronary and left triangular ligaments meet and continue as a ventral mesentery attached to the ventrosuperior aspect of the liver
Gallbladder arises from pars cystica (from the hepatic bud)
- The nervous system develops from the neural plate which appears at the beginning of the third week as thickening of the ectoderm
- Its lateral edges soon elevate to form the neural folds
- With further development, the neural folds continue to elevate, and form a tube known as neural tube
- The neural tube has an enlarged cranial part that forms the brain, and a narrow caudal part that becomes the spinal cord
- The wall of the neural tube at first has a single layer of cells. They multiply and form three layers- ependymal, mantle and marginal layer
Neural tube closure begins at cephalic end
The mantle layer divides into a
- Ventral part, the basal lamina and
- Dorsal part, the alar lamina, separated by a groove, the sulcus limitans
Alar plate gives rise to sensory areas of the spinal cord and the sensory nuclei
Basal plate forms the motor areas of the spinal cord and motor nuclei
The cerebellum and its nuclei develop from the dorsal parts of the alar plate
Inferior olivary and Substantia nigra are sensory nuclei and thus derived from the alar plate
Hypoglossal is a motor nuclei and develops from the basal plate
The Wall of the Spinal Cord
Neuroepithelial Layer | Mantle Layer | Marginal Layer |
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Remember
Forebrain | ||
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(Prosencephalon) | Telencephalon | Cerebral hemispheres |
Diencephalon | Thalamus Hypothalamus Posterior Pituitary Pineal body | |
Midbrain | ||
(Mesencephalon) | No division | Tectum |
Hindbrain | ||
(Rhombencephalon) | Metancephalon Cerebellum | Pons |
Myelencephalon | Medulla | |
Remainder of neural tube | No division | Spinal cord |
3rd ventricle develops from diencephalon
4th ventricle develops from rhombencephalon
- Myelin is formed in the central nervous system by oligodendrocytes
- There are no myelinated fibers in the CNS before the end of the fifth fetal month
- There is no myelination of the forebrain until the seventh fetal month. Most myelination in the telencephalon occurs in the third trimester and postnatally
- The first neurones to acquire myelin sheaths are the olfactory, optic and acoustic cortical areas and the motor cortex (pyramidal cells)
- The last to be myelinated are the projection commissure and association neurons of the cerebral hemispheres
- Myelination is a critical process for the development of the brain because it enhances the speed of neural communication. It occurs most rapidly during the first 2 years of life, but continues until early adulthood
In CNS Myelin is produced by Oligodendrocyte
A single oligodendrocyte myelinates as many as 20 or 30 different CNS axonal segments, each over a length of 1 mm or less
Oligodendrocyte membrane extensions wrap around the axons in a concentric fashion to form the myelin sheath. Myelin proteins include proteolipid protein, myelin basic protein, myelin-associated glycoprotein, and a number of less abundant proteins detectable by electrophoretic separation
Active myelin synthesis starts in utero and continues for the first 2 years of life; slower synthesis continues during childhood and adolescence.
High Yield USMLE Points Lately Asked
Developmental Anomalies of Lungs
- Lobe of Azygos Vein: This lobe appears especially in the right lung in approximately 1% of people. It develops when the apical bronchus grows superiorly, medial to the arch of the azygos vein and produces a linear marking on a radiograph of the lungs
- Sequestration of lung: Lung tissue getting trapped in the core of a lobe is called as intralobar sequestration. Lung tissue completely separated from tracheobronchial tree replacing complete lobe is lobar sequestration
- Potters Syndrome: It is pulmonary Hypoplasia with renal agenesis.
- Thyroglossal Duct Cysts and Sinus: Normally, the thyroglossal duct atrophies and disappears, but a remnant of it may persist and form a cyst in the tongue or in the anterior part of the neck, usually just inferior to the hyoid bone.
- Most thyroglossal duct cysts are observed by the age of 5 years. The swelling produced by a thyroglossal duct cyst usually develops as a painless, progressively enlarging, movable mass. The cyst may contain some thyroid tissue.
- After infection of a cyst, a perforation of the skin occurs, forming a thyroglossal duct sinus that usually opens in the median plane of the neck, anterior to the laryngeal cartilages.
- Ectopic Thyroid Gland: An ectopic thyroid gland is usually located along the course of the thyroglossal duct. Lingual thyroid tissue is the most common of ectopic thyroid tissues. Other sites:
- Larynx
- Trachea
- Esophagus
- Pericardium
- Pleura
- Ovaries
Struma Ovary:
- It is a rare ovarian tumor defined by the presence of thyroid tissue
- Most commonly, they occur as part of a teratoma, but may occasionally be encountered with serous or mucinous cystadenomas
- Benign strumosis is a rare version of mature thyroid tissue implants throughout the peritoneal cavity
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Developmental Anomalies of Tongue
Ankyloglossia: The lingual frenulum normally connects the inferior surface of the tongue to the floor of the mouth. Sometimes the frenulum is short and extends to the tip of the tongue. This interferes with its free protrusion and may make breastfeeding difficult. A short frenulum usually stretches with time, making surgical correction of the anomaly unnecessary.
Macroglossia: An excessively large tongue is not common. Amyloidosis is associated with Macroglossia
- Microglossia: An abnormally small tongue is extremely rare and is usually associated with micrognathia (underdeveloped mandible and recession of the chin) and limb defects (Hanhart’s syndrome)
- Bifid Tongue
- Fissured tongue
- Laryngeal Atresia: This anomaly results from failure of recanalization of the larynx, which causes obstruction of the upper fetal airway. Distal to the region of atresia (blockage) or stenosis (narrowing), the airways become dilated, the lungs are enlarged and echogenic
- Laryngeal web: Results from incomplete recanalization of the larynx during the 10th week. A membranous web forms at the level of the vocal folds, partially obstructing the airway
- Laryngoptosis: Larynx is situated lower down in neck
- Laryngeocele: Excessive enlargement of saccule of larynx.
Developmental Anomalies of Trachea
- Tracheoesophageal Fistula:
- A fistula between the trachea and esophagus
- Most affected infants are males
- In more than 85% of cases, the tracheoesophageal fistula (TEF) is associated with esophageal atresia
- A TEF results from incomplete division of the cranial part of the foregut into respiratory and esophageal parts during the fourth week
- Incomplete fusion of the tracheoesophageal folds results in a defective tracheoesophageal septum and a TEF between the trachea and esophagus
Polyhydramnios is often associated with esophageal atresia. The excess amniotic fluid develops because fluid cannot pass to the stomach and intestines for absorption and subsequent transfer through the placenta to the mother’s blood
Developmental Anomalies of Cardiovascular System
- Ectopia cordis: Non union of sternal plates exposing the heart to surface
- Dextrocardia: If the heart tube bends to the left instead of to the right, the heart is displaced to the right and there is transposition — the heart and its vessels are reversed left to right as in a mirror image. Dextrocardia is the most frequent positional abnormality of the heart. In isolated dextrocardia, the abnormal position of the heart is not accompanied by displacement of other viscera
- Maybe associated with
Situs Inversus/ Kartageners Syndrome/Immotile Cilia Syndrome
- Atrial Septal Defects: An atrial septal defect (ASD) is a common congenital heart anomaly and occurs more frequently in females than in males. The most common form of ASD is patent oval foramen. A small isolated patent oval foramen is of no hemodynamic significance; however, if there are other defects (e.g. pulmonary stenosis or atresia), blood is shunted through the oval foramen into the left atrium and produces cyanosis.
- Ventricular Septal Defects: VSDs are the most common type of CHD, accounting for approximately 25% of defects. VSDs occur more frequently in males than in females. VSDs may occur in any part of the IV septum but membranous VSD is the most common type frequently, small VSDs close spontaneously. Most people with a large VSD have massive left-to-right shunting of blood. Muscular VSD is a less common type of defect and may appear anywhere in the muscular part of the interventricular septum. Sometimes there are multiple small defects, producing what is sometimes called the ‘Swiss cheese’ VSD.
- Cor biloculare: Two chambered heart
- Cor Triloculare: Three chambered heart
- L. Cor triloculare biatriatum: (Two atria, one ventricle): Absence of the IV septum-single ventricle or common ventricle-resulting from failure of the IV septum to form is extremely rare and results in a three-chambered heart (L. cor triloculare biatriatum).
- Transposition of the Great Arteries: TGA is the most common cause of cyanotic heart disease in newborn infants. TGA is often associated with other cardiac anomalies (e.g. ASD and VSD).
In typical cases, the aorta lies anterior and to the right of the pulmonary trunk and arises from the morphologic right ventricle, whereas the pulmonary trunk arises from the morphologic left ventricle. The aorticopulmonary septum fails to pursue a spiral course during partitioning of the bulbus cordis and TA
This defect is thought to result from failure of the conus arteriosus to develop normally during incorporation of the bulbus cordis into the ventricles
Recent studies suggest that defective migration of neural crest cells may also be involved.
- Tetralogy of Fallot: This classic group of four cardiac defects
- Pulmonary stenosis (Obstruction of right ventricular outflow)
- VSD
- Dextroposition of aorta (Overriding or straddling aorta)
- Right ventricular hypertrophy
- Coarctation of the Aorta: Aortic coarctation (constriction) occurs in approximately 10% of children and an adult with CHDs. Coarctation is characterized by an aortic constriction of varying length. Most coarctations occur distal to the origin of the left subclavian artery at the entrance of the DA (juxtaductal coarctation). The classification into preductal and postductal coarctations is commonly used. Coarctation of the aorta occurs twice as often in males as in females and is associated with a bicuspid aortic valve in 70% of cases.
- Cystic hygroma: Large swellings usually appear in the inferolateral part of the neck and consist of large single or multilocular, fluid-filled cavities. Hygromas maybe present at birth, but they often enlarge and become evident during infancy. Most hygromas appear to be derived from abnormal transformation of the jugular lymph sacs
- Represents lymphatic venous anastamotic failure
- Located usually in the neck at lower in posterior triangle
- Brilliantly translucent
Developmental Anomalies of GIT
- Esophageal Atresia: Esophageal atresia is associated with tracheoesophageal fistula in more than 85% of cases. Atresia may occur as a separate anomaly, but this is less common. Esophageal atresia results from deviation of the tracheoesophageal septum in a posterior direction as a result there is incomplete separation of the esophagus from the laryngotracheal tube. A fetus with esophageal atresia is unable to swallow amniotic fluid; consequently, this fluid cannot pass to the intestine for absorption and transfer through the placenta to the maternal blood for disposal. This results in polyhydramnios
- Esophageal Stenosis: Narrowing of the lumen of the esophagus can be anywhere along the esophagus, but it usually occurs in its distal third, either as a web or as a long segment of esophagus with a thread like lumen. Stenosis usually results from incomplete recanalization of the esophagus.
- Short Esophagus (Congenital Hiatal Hernia): Initially the esophagus is very short. Its failure to elongate sufficiently as the neck and thorax develop results in displacement of part of the stomach superiorly through the esophageal hiatus into the thorax-congenital hiatal hernia. Most hiatal hernias occur long after birth, usually in middle-aged people.
- Duodenal Atresia: Complete occlusion of the lumen of the duodenum. If recanalization of the lumen fails to occur a short segment of the duodenum is occluded. The blockage occurs nearly always at the junction of the bile and pancreatic ducts (hepatopancreatic ampulla) but occasionally involves the horizontal (third) part of the duodenum.
- In infants with duodenal atresia, vomiting begins a few hours after birth. The vomitus almost always contains bile; duodenal atresia may occur as an isolated anomaly, but other congenital anomalies are often associated with it, e.g. anular pancreas cardiovascular abnormalities, anorectal anomalies, and malrotation. Importantly, approximately one third of affected infants have Down syndrome and an additional 20% are premature. Duodenal atresia is associated with bilious emesis (vomiting of bile) because the blockage occurs distal to the opening of the bile duct. Polyhydramnios also occurs because duodenal atresia prevents normal intestinal absorption of swallowed amniotic fluid. The diagnosis of duodenal atresia is suggested by the presence of a ‘double bubble‘ sign on plain radiographs or ultrasound scans. This appearance is caused by a distended, gas-filled stomach and proximal duodenum.
- Riedels Lobe: A tongue like extension of right lobe of liver.
- Phrygian cap: Fundus of the gallbladder folded upon itself giving rise to an appearance of cap worn by people of an ancient Asian community of Phrygia.
- Moynihans Hump: Normally the arterial supply of gallbladder is from cystic artery which is a branch of Right hepatic artery. Sometimes an accessory cystic artery is also seen to arise from either Gastroduodenal or right hepatic artery
The Right hepatic artery takes a tortuous course called ‘caterpillar turn’ or ‘Moynihans hump.’ This can be a source of profuse bleeding.
- Intrahepatic gallbladder is one of the ectopic locations of the gallbladder. The gallbladder is usually intrahepatic during its embryologic period and becomes extrahepatic later on in its development. In adults approximately 60% of intrahepatic gallbladders are associated with gallstones
- Double and Triple gallbladders have been reported, the latter being extremely rare. Double gallbladders may share a common cystic duct and be completely separated, or they maybe divided by a septum. When they do not share a common outlet, the cystic ducts of double or triple gallbladders open separately into the common bile duct or, less commonly, into the right hepatic duct
- Choledochal Cyst: Choledochal cysts are congenital cystic dilatations of the extrahepatic and/or intrahepatic biliary tree. They are rare. Originally, they were described as cystic dilatations of the extrahepatic duct system. Subsequently this classification was extended to include the frequent association with cystic dilatation of the duct system within the liver, a condition described in 1958 and now known as Caroli’s disease.
- Extrahepatic Biliary Atresia: This is the most serious anomaly of the extrahepatic biliary system and occurs in one in 10,000 to 15,000 live births
- The most common form of extrahepatic biliary atresia is obliteration of the bile ducts at or superior to the porta hepatis
- Biliary atresia could result from a failure of the remodeling process at the hepatic hilum or from infections or immunologic reactions during late fetal development
- Jaundice occurs soon after birth and stools are acholic (clay colored).
- Accessory Pancreatic Tissue: Accessory pancreatic tissue is most often located in
- The wall of the stomach
- Wall of duodenum
- In an ileal diverticulum a/Meckel diverticulum
- Anular Pancreas:
- May cause duodenal obstruction
- The ring like or anular part of the pancreas consists of a thin, flat band of pancreatic tissue surrounding the descending or second part of the duodenum.
- An anular pancreas may cause obstruction of the duodenum either shortly after birth or later. Infants present with symptoms of complete or partial bowel obstruction. An anular pancreas maybe associated with
- Down syndrome
- Intestinal atresia
- Imperforate anus
- Pancreatitis
- Malrotation
- Infants with these large omphaloceles often suffer from pulmonary and thoracic hypoplasia and a delayed closure is a better clinical decision. The covering of the omphalocele is by amnion and peritoneum.
- Umbilical Hernia: When the intestines return to the abdominal cavity during the 10th week and then herniate through an imperfectly closed umbilicus, an umbilical hernia forms. This common type of hernia is different from an omphalocele. In an umbilical hernia, the protruding mass (usually the greater omentum and part of the small intestine) is covered by subcutaneous tissue and skin. The defect through which the hernia occurs is in the linea alba. The hernia protrudes during crying, straining, or coughing and can be easily reduced through the fibrous ring at the umbilicus. Surgery is not usually performed unless the hernia persists to the age of 3 to 5 years.
- Gastroschisis: This anomaly is a relatively uncommon congenital abdominal wall defect. Gastroschisis results from a defect lateral to the median plane of the anterior abdominal wall. The linear defect permits extrusion of the abdominal viscera without involving the umbilical cord. The viscera protrude into the amniotic cavity and are bathed by amniotic fluid.
Anomalies of the Midgut
- Nonrotation occurs when the intestine does not rotate as it re-enters the abdomen. As a result, the caudal limb of the midgut loop returns to the abdomen first and the small intestines lie on the right side of the abdomen and the entire large intestine is on the left and the cecum lies just inferior to the pylorus of the stomach. The cecum is fixed to the posterolateral abdominal wall by peritoneal bands that pass over the duodenum. These bands and the volvulus (twisting) of the intestines cause duodenal obstruction. When midgut volvulus occurs, the superior mesenteric artery maybe obstructed, resulting in infarction and gangrene of the intestine supplied by it. Infants with intestinal malrotation are prone to volvulus and present with bilious emesis.
- Reversed Rotation: In very unusual cases, the midgut loop rotates in a clockwise rather than a counterclockwise direction. As a result, the duodenum lies anterior to the superior mesenteric artery rather than posterior to it, and the transverse colon lies posterior instead of anterior to it. In these infants, the transverse colon maybe obstructed by pressure from the superior mesenteric artery.
- Congenital Megacolon or Hirschsprung Disease:Infants with congenital megacolon or Hirschsprung’s disease lack autonomic ganglion cells in the myenteric plexus distal to the dilated segment of colon(Hirschsprung’s disease is the congenital absence of enteric neurons in the submucosal and myenteric plexuses, due to an arrest of the embryonic caudal migration of the enteric neurons along the gut. The aganglionic segment remains contracted, dilating the proximal normal bowelThe severity of symptoms and the age at diagnosis are related to the length of the aganglionic segment. Involvement of the rectum or additional parts of the colon results in constipation or obstipation in infancy, requiring emergent resection of the a ganglionic bowel and a pull-through anastomosis to the anus.)
- 22Imperforate Anus and Anorectal Anomalies: Imperforate anus occurs approximately once in every 5000 newborn infants and is more common in males. Most anorectal anomalies result from abnormal development of the urorectal septum, resulting in incomplete separation of the cloaca into urogenital and anorectal portions. There is normally a temporary communication between the rectum and anal canal dorsally from the bladder and urethra ventrally but it closes when the urorectal septum fuses with the cloacal membrane.
- Anal Agenesis, with or without a Fistula: The anal canal may end blindly or there maybe an ectopic anus or an anoperineal fistula that opens into the perineum. The abnormal canal may, however, open into the vagina in females or the urethra in males.
- Anal Stenosis: The anus is in the normal position, but the anus and anal canal are narrow. This anomaly is probably caused by a slight dorsal deviation of the urorectal septum as it grows caudally to fuse with the cloacal membrane. As a result, the anal canal and anal membrane are small.
USMLE Case Scenario
Embryologically, The Gut rotates and the rotation occurs in a way that:
- The large intestine rotates in a clockwise manner around the axis of the celiac trunk
- The large intestine rotates in a clockwise manner around the axis of the superior mesenteric artery
- The large intestine rotates in a clockwise manner around the axis of the inferior mesenteric artery
- The large intestine rotates in a counterclockwise manner around the axis of the celiac trunk
- The large intestine rotates in a counterclockwise manner around the axis of the superior mesenteric artery
- The large intestine rotates in a counterclockwise manner around the axis of the inferior mesenteric artery
Ans. 5. The large intestine rotates in a counterclockwise manner around the axis of the superior mesenteric artery
Developmental Anomalies of Urinary Tract
- Horseshoe Kidney: In 0. 2% of the populations, the poles of the kidneys are fused; usually the inferior poles fuse. The large U-shaped kidney usually lies in the hypogastrium, anterior to the inferior lumbar vertebrae. Normal Persons with Turner’s syndrome have horseshoe kidneys.
- Ectopic Ureter: An ectopic ureter does not enter the urinary bladder. In males, ectopic ureters usually open into the neck of the bladder or into the prostatic part of the urethra, but they may enter the ductus deferens, prostatic utricle, or seminal gland. In females, ectopic ureters may open into the
- Bladder neck
- Urethra
- Vagina
- Vestibule of the vagina
Cystic Kidney Diseases
- In autosomal recessive polycystic kidney disease, diagnosed at birth or in utero by ultrasonography, both kidneys contain many hundreds of small cysts which result in renal insufficiency.
- Multicystic dysplastic kidney disease results from dysmorphology during development of the renal system. The outcome for children with multicystic dysplastic kidney disease is generally good because the disease is unilateral in 75% of the cases. In multicystic dysplastic kidney disease, fewer cysts are seen than in autosomal recessive polycystic kidney disease and they range in size from a few millimeters to many centimeters in the same kidney.
- Congenital Adrenal Hyperplasia (CAH): An abnormal increase in the cells of the suprarenal cortex results in excessive androgen production during the fetal period. In females, this usually causes masculinization of the external genitalia. Affected male infants have normal external genitalia, and the syndrome may go undetected in early infancy. Later in childhood in both sexes, androgen excess leads to rapid growth and accelerated skeletal maturation. CAH is a group of autosomal recessive disorders that result in virilization of female fetuses.
Developmental Anomalies of Genital System
- Mesonephric Duct Remnants in MalesThe cranial end of the mesonephric duct may persist as an appendix of the epididymis, which is usually attached to the head of the epididymis Caudal to the efferent ductules, some mesonephric tubules may persist as a small body, the paradidymis. It forms
- Epididymis
- Ductus deferens
- Seminal vesicles
- Ejaculatory ducts
- Appendix epididymis
- Mesonephric Duct Remnants in FemalesThe cranial end of the mesonephric duct may persist as an appendix vesiculosa. A few blind tubules and a duct, the epoophoron, correspond to the efferent ductules and duct of the epididymis in the male. The epoophoron may persist in the mesovarium between the ovary and uterine tube. Closer to the uterus, some rudimentary tubules may persist as the paroophoron. Parts of the mesonephric duct, corresponding to the ductus deferens and ejaculatory duct, may persist as Gartner’s duct cysts between the layers of the broad ligament along the lateral wall of the uterus and in the wall of the vagina.
- Paramesonephric Duct Remnants in MalesThe cranial end of the paramesonephric duct may persist as a vesicular appendix of the testis, which is attached to the superior pole of the testisThe prostatic utricle, a small saclike structure that opens into the prostatic urethra, is homologous to the vagina.
- Paramesonephric Duct Remnants in Females
- Part of the cranial end of the paramesonephric duct that does not contribute to the infundibulum of the uterine tube may persist as a vesicular appendage it forms
- Uterus
- Cervix
- Uterine tubes
- Hydatid of morgagni
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- The term cryptorchidism (Greek cryptos = hidden, orchis = testis) should be reserved for impalpable, usually abdominal, testes
- There is a higher incidence of undescended testes in premature than in full-term babies
- Two-thirds of undescended testes in newborn infants will descend, usually by 6 weeks in term and 3 months in preterm babies
- There is an increased incidence of cryptorchidism in anencephalics and other cerebral anomalies.
- Ectopic Testes: After traversing the inguinal canal, the testis may deviate from its usual path of descent and lodge in various abnormal locations
- Interstitial (external to aponeurosis of external oblique muscle)
- In the proximal part of the medial thigh
- Dorsal to the Penis
- On the opposite side (crossed ectopia)
- Exstrophy of the bladder results from a rare ventral body wall defect through which the posterior wall of the urinary bladder protrudes onto the abdominal wall. Epispadias is a common associated anomaly in males; the urethra opens on the dorsum of the penis.
Developmental Anomalies of CNS
- Spina Bifida: The original defect lies in the vertebrae when their laminae fail to cover the spinal cord dorsally. Spina bifida maybe simple or complicated. Complicated Spina bifida is associated with involvement of the cord and its membranes
- Rarely do the two halves of the vertebral body fail to fuse and the spinal cord protrudes anteriorly through the gap. This rarity is called as anterior spina bifida
- Spina bifida occulta: Here the spinal cord is normal. The defect is not manifest externally and usually a tuft of hair is present on the skin over the affected area
- Meningocele: The Arachnoid and the Piamater covering the spinal cord protrude through the opening of the bifid spine and form a cystic swelling
- Meningomyelocele: Here the spinal cord along with its meninges and the spinal nerves are seen to protrude. It is a more serious condition owing to development of infection of the cord itself
- This condition is associated with displacement of medulla and a part of cerebellum which cause obstruction of the foramen magnum producing hydrocephalus. An association of hydrocephalus and Meningomyelocele is called Arnold Chiari malformation
- Syringomyelia: Once the central canal of the spinal cord is distended with excessive fluid it is called Syringomyelia
- Myelomalacia: Abnormal softening of spinal cord. Usually seen after trauma to spinal cord
- In Syringomyelia there is softening of the spinal cord and the central canal becomes very wide at lesion in this position will interrupt the pain and temperature fibers which pass in front of the central canal as they cross from one side to another
- Syringomyelia usually occurs in the lower cervical and the upper thoracic regions of the spinal cord and the loss of pain and temperature
- Only the fibers of the pain and temperature which pass in front of the central canal are injured: the lateral spinothalamic tracts ‘themselves’ remain normal and there is no loss of pain and temperature in the lower limbs
- Touch can be felt in the area of the skin in which pain and temperature are lost: this condition in which pain and temperature is lost while touch is nearly normal called Dissociated sensory loss.
USMLE Case Scenario
Which of the following embryonic structures gives rise to the adrenal cortex?
- Ectoderm
- Endoderm
- Mesoderm
- Mesonephros
Ans. 3. Mesoderm
Types of Neurons Based on Poles
Unipolar Neurons
They have only one pole
Both Axon and Dendrons arise by a common stem.
Present in
- Fetal life
- Posterior root ganglion
- Sensory nucleus of the fifth cranial nerve
Bipolar Neurons
They have two poles
Axon and Dendron lie at opposite poles
Present in
- Cochlear ganglion of the eight nerves
- Vestibular ganglion of the eight nerves
- Retina
- Olfactory nerve
Multipolar Neurons
They have multiple poles
The Axon and all other Dendrons form multiple poles
Present in
- The spinal cord
- Cerebral cortex
- Cortex of cerebellum
- Leptotene: Chromosomes become visible
- Zygotene: Pairing of chromosomes
- Pachytene: Tetrad formation, crossing over, chiasmata formation
- Diplotene: Chromosomes break
- Metaphase: Spindle formation
- Anaphase: Chromosomes move from equator to poles
- Telophase: Chromosomes move completely to opposite sides
Sex Chromatin or Barr body
Of the two X-chromosomes in a Female only one is functionally active. The other (Inactive) X-chromosome forms a mass of heterochromatin that lies just under the nuclear membrane. This mass of heterochromatin can be identified in suitable preparations and can be useful in determining whether a particular tissue belongs to a male or a female. Because of this association with sex this mass of heterochromatin is called the SEX CHROMATING. It is also called a BARR-BODY after the name of the scientist who first discovered it.
- In NEURONS it forms a rounded mass lying very close to the nucleolus and is therefore called a NUCLEOLAR SATELLITE.
- In NEUTROPHIL LEUCOCYTES it may appear as an isolated round mass attached to the rest of the nucleus by a narrow band, thus resembling the appearance of a DRUM-STICK. Rarely, some individuals may have more than two X-chromosomes. In these cases only one X-chromosome is active (and hence euchromatic) while others are represented by masses of heterochromatin.
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Cell Division
The number of chromosomes found in somatic cells is constant and is termed the diploid (2n) number. Each gamete, however, has only half the diploid number and is said to be haploid (n). In order to maintain this regularity, two types of cell division occur: mitosis, which is the cell division occurring in somatic tissues during growth and repair, and meiosis, which is the specialized form of cell division occurring when gametes form.
Mitosis
The function of mitosis is to distribute and maintain the continuity of the genetic material in every cell of the body. This process consists of a number of different phases, which results in an equal distribution of the chromosomes to the two daughter cells. The cell cycle has four stages: mitosis (M), gap1 (G1), synthesis (S), and gap2 (G2). The G1 phase follows mitosis, during which RNA and protein synthesis occurs. S is the period during which DNA replication takes place and the DNA content of the cell doubles, and G2 is the period during which energy requirements for cell division are built-up and any repair of errors in DNA synthesis takes place.
This process occurs only during the formation of the gametes and results in four daughter cells, each with the haploid number of chromosomes. In males each primary spermatocyte forms four functional spermatids that develop into sperm, while in females each oocyte forms only one ovum, the remaining products of meiosis being nonfunctional polar bodies.
Lyonization
In females, the sex chromosomes are identical in size and are genetically homologous chromosomes (as in the case of autosomes); however, in the normal diploid interphase cell, one of the X’s forms a condensed heterochromatic body called the Barr body. These condensations, together with evidence from coat color pattern in mice, led Lyon to hypothesize X-inactivation.
She Stated
- In each somatic cell there is inactivation of all but one of the X-chromosomes;
- This process occurs early in development and is random with respect to maternally or paternally derived X-chromosomes in different cells; and
- Once a particular X is inactive, it is inactive in all daughter cells.
Important Points about Skin
- The Skin has stratified squamous epithelium
- Classically epidermis has four layers
- Normal turn over of epidermis is 4 weeks
- Skin doubling time is 4 weeks
- Stratum Germinativium composed of stratum Basale and Stratum Spinosum
- Stratum Granulosum (Granular cell layer)
- Stratum Lucidum (Clear cell layer)
- Stratum Corneum (horny cell layer)
- Stratum Germinativium is also called as Malphigian layer composed of
- Basal cell layer
- Prickle cell layer (stratum spinosum)
The Basal cell layer is composed of single layer of columnar cells resting on a clear wavy basement membrane From the basal borders of these cells Cytoplasmic processes extend anchoring the epidermis to dermis Melanocytes are present here.- Acantholytic cells are present here
- Dermatophytes are present here
- It is underdeveloped in VLBW infants
The prickle cell layer (stratum spinosum) consists of 4–6 layers of cells which are polygonal and connected together by tonofilaments giving them a prickly appearance.
- Stratum Granulosum
- Consists of 3–4 layers of flattened cells rich in keratohyaline granules
- The keratohyaline granules eventually fill much of the cell, and it is these granules which give the cells of the stratum Granulosum its granular appearance
- The keratohyaline granules contain a protein called filaggrin, the function of which appears to be to bind the tonofibrils together, converting them into keratin
- Stratum Lucidum
- Consists of few layers of dead, non nucleated cells without cell boundaries
- These cells are rich in Eleidin granules
- Stratum Corneum
- It is the most superficial layer of epidermis
- It is made of flat, dead cornified cells which have horny scales
- They are continuously shed from the surface and replaced by newer cells
- The Papillary layer or the loose connective tissue layer
- The Reticular layer or the deeper layer
The Hypodermis is continuous with the dermis. It is formed of loose CT rich in blood vessels, loose CT, nerve endings.
Cells in Skin are
‘Langerhans Cells’
- Are located primarily in the stratum spinosum
- They function in the immune system as antigen presenting cells
- They stain selectively with gold chloride and contain numerous rod like or racket-shaped Cytoplasmic granules (Birbeck’s granules)
‘Merkel Cells’
- Are located in the stratum basale
- They contain granules which contain catecholamines
- The base of a Merkel cell makes contact with the expanded terminal disk of a nerve fiber, forming a special receptor which functions as a mechanoreceptor (detection of touch)
‘Dendritic Cells’
- Are found throughout the epidermis
- They are antigen presenting cells
EPITHELIUM
Simple Squamous Epithelium
- Alveoli of lungs
- Mesothelium of pleura, peritoneum and pericardium
- Endothelium of heart and blood vessels
Simple Cuboidal Epithelium
- Lining of the thyroid follicles
- Germinal epithelium of ovary
- Anterior surface of lens of eye
Simple Columnar Epithelium
- The lining of stomach
- Intestines
- Gallbladder
Simple Columnar Ciliated
- Fallopian tubes and the uterus
- Central canal of spinal cord
- Osseous part of eustachian tube
It is a simple type of columnar cells resting on a clear wavy basement membrane. The cells are crowded over each other and appear multilayered. The nuclei are arranged at different levels, some situated basal and others centrally as a result of which a false impression of multilayered cells is created. However, most of the cells reach the basement membrane. The cells maybe ciliated or nonciliated
With cilia
- Nasal cavity, nasal air sinuses, nasopharynx, larynx, trachea and bronchi
- Eustachian tube in its cartilaginous parts
Without cilia
- Vas deferens
- Part of male urethra
Stratified Squamous Epithelium
The surface of the cells maybe keratinized (Protective function) as in case of
- Epidermis of skin
- External ear
- External nose
The surface of the cells maybe without keratin called Nonkeratinized as in case of
- Esophagus
- Tongue
- True vocal cords
- Cornea
- Tonsil
Stratified Columnar Epithelium
- Conjunctival fornicies
- Penile part of male urethra
- Anorectal junction
Transitional Epithelium
- It is a type of epithelium composed of multiple cell layers
- They have extra reserve of cell membrane
- The top cell layers are broader
- The intermediate cell layers are polyhedral without intercellular bridges separated by mucus like substance. The cells can undergo transition in relaxed and contracted state. In the relaxed state the number of layers is 6–8 while as in the contracted state it is 2–3 layers
- The basal cell layers are cuboidal.
It is present in
- Calyces
- Ureter
- Urinary bladder
- UV junction
- Male urethra
Gland | Duct | Type of Gland | Duct opening |
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| Vestibule of mouth opposite second upper molar |
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| On the floor of mouth on summit of sublingual papilla at the side of frenulum of tongue |
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| On the floor of mouth on summit of sublingual papilla |
Structures within Parotid Gland
- External carotid artery
- Retromandibular vein
- Facial nerve
Questions Frequenly asked from Histology of Liver
- Classic Hepatic Lobule: This model is based on the direction of blood flow. In sections, liver substructure exhibits a pattern of interlocking hexagons; each of these is a classic lobule. Whereas lobules in pigs are defined by a sheath of connective tissue, there is less connective tissue in humans and the lobule boundaries are indistinct. The central vein at its center and the alternating hepatocyte plates and sinusoids that lie between them.
- Portal Canal/triad: One triad occupies a potential space (portal space) at each of the 6 corners of the lobule. Each triad contains 3 main elements surrounded by connective tissue: a portal venule (a branch of the portal vein), a hepatic arteriole (a branch of the hepatic artery) and a bile ductule (a tributary of the larger bile ducts). A lymphatic vessel may also be seen. In the portal canal blood vessels and bile ductules are separated by a space called as Space of Mall
- Portallobule: This model is based mainly on the direction of bile flow, which is opposite to that of blood. From this perspective, the liver parenchyma is divided into interlocking triangles, each of which has a portal triad at the center and a central vein at each of its 3 comers
- Hepatic lobule: It is the structural unit of liver. It has a central vein. A single vein marks the center of each lobule. This vessel is easily distinguished from those in the portal triad by its larger opening and lack of a connective tissue investment.
- Kuffercells are Reticuloendothelial cells of liver
- Itto cells are fat storing cells in liver
- 'Space of Dissie’ and ‘Space of Mall’ are seen in Liver
Important Histological Features: (USMLE Favorite)
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Cells of Stomach
The Mucus neck cells
- Called so as they are present in the necks of glands
- They secrete mucin which serves as a protective layer against HCL
- They are low columnar with basal flat nuclei
The Chief cells (The Peptic cells or the Zymogen cells)
- Called as chief because they line the main part of the body of the gland
- They are low columnar with basal round nuclei
- They secrete pepsinogen
Oxyntic Cells (Parietal Cells)
- They are scattered in between peptic cells
- They are highly acidophilic
- Intrinsic factor of Castle is secreted by parietal cells
- They secrete HCL
- They contain secretory canaliculi and are rounded
The Argentaffin Cells
- They are chromaffin positive and stain positive with Silver salts
- They also contain acidophilic granules and are oval in shape
Cells of Intestine
Simple Columnar Cells
- Line the villi and crypts
- Have free brush border due to presence of microvilli to increase surface area
Goblet Cells
- Are also present in the villi and crypts
- They are unicellular glands
- They are flask shaped
- They secrete mucin
Paneth Cells
- Are acidophilic
- Secrete intestinal enzymes
- Rich in Rough ER
Argentaffin cells
- These are cells with silver staining properties
- They secrete serotonin
Diffuse Lymphatic Tissue, Isolated Lymphatic Nodules
The diffuse lymphatic tissue is a collection of lymphatic tissue in:
- Alimentary tract
- Respiratory tract
- Genitourinary tract
The lymphoid tissue is deposited randomly in the subepithelial layers and placed strategically so as to detect and destroy the pathogenic agents instantaneously and effectively. Located in adventitia
Functioning in close collaboration is other set of localized concretions of lymphocytes in the form of follicles and nodules such as:
- Pharyngeal tonsils
- Palatine tonsils
- Lingual tonsils
- Peyers patches in the small intestine especially in the ileum
- Lymphoid follicles in appendix/abdominal tonsil
Remember frequently asked Terms in USMLE
Eponyms | Description |
Bowman’s capsule | Glomerular capsule of the kidney seen on histology slides |
Bowman’s membrane | Layer in the cornea below epithelium seen on histology slides |
Brunner’s glands | Glands in the duodenum seen on histology slides |
Bundle of His | Atrioventricular bundle |
Cords of Billroth | Splenic cords of the spleen seen on histology slides |
Crypts of Lieberkuhn | Epithelial glands in the small intestine seen on histology slides |
Descemet’s membrane | Limiting layer of the cornea seen on histology slides |
Ducts of Bellini | Papillary duct of the kidney seen on histology slides |
Ducts of Luschka | Small ducts found in the connective tissue between the gallbladder and the liver |
Golgi aparatus | Intracellular organelle |
Golgi tendon organ | Sensory nerve ending embedded in a tendon for proprioception |
Graafian follicle | Tertiary follicle of an ovary seen on a histology slide |
Haversian canal | Central canal of an osteon of bone seen on a histology slide |
Haversian system | Osteon of bone seen on a histology slide |
Islets of Langerhans | Pancreatic islets of the pancreas seen on histology slides |
Leydig cells | Interstitial cells of the testis |
Loop of Henle | U shaped loop in the nephron of the kidney |
Krause end bulbs | Cylindrical/oval sensory receptor |
Malpighian corpuscle | Renal corpuscle of the kidney seen on histology slides |
Meissner’s corpuscle | Mechanoreceptor |
Meissner ‘s plexus | Submucosal plexus |
Merkel’s disk | Tactile receptor |
Moll’s gland | Glands of the conjunctiva |
Nissl bodies | Rough endoplasmic reticulum of a neuron |
Node of Ranvier | Area between two Schwann cells covering nerve fibers with axon which is not covered by myelin |
Organ of Corti | Small organ of sound transduction; spiral organ |
Pacinian corpuscle | Lamellar corpuscle |
Peyer’s patches | Aggregates of lymphatic tissue in the ileum seen on histology slides |
Purkinje fibers | Part of the conducting system of the heart |
Renal columns of Bertin | Renal columns seen on histology slides |
Ruffini’s corpuscle | Sensory receptor |
Space of Disse | Perisinosoidal space of the liver seen on histology slides |
Volkmann’s canals | Perforating canals of bone |
Wharton’s jelly | Mucous connective tissue seen in umbilical cord |
Upper Limb Brachial Plexus
- C5 and C6 roots join to form the upper trunk
- C7 root alone forms the middle trunk
- C8 and T1 roots join to form the lower trunk
Each trunk divides into an anterior and posterior division:
- All the posterior divisions join to form the posterior cord
- The upper two anterior divisions join to form the lateral cord
- The lowest anterior division alone forms the medial cord
Branches of the Brachial Plexus
Branches from the roots
- Nerve to serratus anterior (C5, C6, C7)
- Dorsal scapular nerve (C5)
- Muscular branches to the 3 scalene muscles
Branches from the trunks
- Suprascapular nerve (C5, C6)
- Subclavius nerve (C5, C6)
Branches from the cords
Medial cord
- Medial head of median nerve (C8, T1)
- Medial pectoral (C8, T1)
- Ulnar nerve (C8, T1)
- Median cutaneous nerve of forearm (C8, T1)
- Medial cutaneous nerve of arm (T1)
Lateral cord
- Lateral pectoral (C5, C6, C7)
- Lateral head of median (C5, C6, C7)
- Musculocutaneous (C5, C6, C7)
Posterior cord
- Radial (C5, C6, C7, C8, T1)
- Axillary (C5, C6)
- Nerve to latissimus dorsi (C6, C7, C8)
- Subscapular Upper (C5, C6)
- Subscapular lower
Upper trunk deformity is called
- Erbs palsy or policemans
- Waiters tip
- Porter tip deformity
Lower trunk deformity is called Klumpkes palsy
Ulnar nerve ‘Musicians Nerve’
- Ulnar nerve supplies medial 1/3 of palm. (Hypothenar area)
- Ulnar nerve in hand supplies:
- 3, 4 Lumbricals
- Palmar and dorsal interosei
- Adductor pollicis
- Hypothenar muscles
- Ulnar nerve in hand supplies flexor carpi ulnaris and medial half of flexor digitorum profundusLesion of ulnar nerve causes:
- Weakness of ulnar deviation
- Weakness of wrist flexion
- Adductor pollicis paralysis with loss of thumb adduction
In Ulnar Nerve Palsy there is
- Positive card test
- Positive book test/Froment sign
- Positive Egawas test
- Ulnar claw hand
Median nerve: ‘Laborers nerve’, Eye of hand
- Does not supply arm
- Supplies all flexors except flexor carpi ulnaris and medial half of flexor digitorum profundus in forearm
- Supplies thenar eminence
- Lumbrical 1 and 2
- Opponens pollicis
- Abductor pollicis brevis
- Flexor pollicis brevis in hand. (LOAF)
Implicated in:
Lunate dislocation
- Ape thumb deformity
- Carpal tunnel syndrome
- Pointing index
- Pen test is positive in median nerve injury
- Loss of opposition and abduction of thumb
Carpal Tunnel Syndrome
Affects the median nerve. Patients often note a tingling, a loss of sensation, or diminished sensation in the digits. There is also often a loss of coordination and strength in the thumb, because the median nerve also sends fibers to the abductor pollicis brevis, flexor pollicis brevis, and the opponens pollicis. A final function of the median nerve distal to the carpal tunnel is control of the first and second lumbricals which function to flex digits two and three at the metacarpophalangeal joints and extend interphalangeal joints of the same digits.
Supplies:
- Extensor compartment of arm, forearm
- Triceps
- Anconeus and extensors of forearm. Extension of MCP joint
- Injury to RN Causes
- Wrist drop
- Saturday night palsy/crutch palsy
- Commonly injured in Radial groove
USMLE Case Scenario
A 43-year-old man suffered an injury in his left upper limb. His radial nerve was injured. The radial nerve is at greatest risk for injury with:
- Fracture of the surgical neck of the humerus
- Fracture of the shaft of the humerus
- Supracondylar fracture of the humerus
- Olecranon fractures
Ans. 2. Fracture of the shaft of the humerus
Remember
The radial nerve lies in proximity to the humerus as it courses laterally at the junction of the middle and distal thirds of the shaft of the humerus. Therefore, it is at greatest risk of injury in shaft fractures.
Common Questions in Surgical Anatomy (Hot Questions)
- In ‘supracondylar fracture’ of humerus triangular relationship of three bony prominences is not disturbed. In elbow dislocation it is disturbed
- The ‘shoulder joint’ is the most commonly dislocated major joint in the body
- MC dislocation is inferior
- In subacromial bursitis, person feels pain when arm is abducted. ‘Dawbarns sign’ is seen in subacromial bursitis
- PIN (Posterior interosseous nerve) is a branch of radial nerve. No wrist drop is seen in injury to PIN
- If posterior medial aspect of elbow is banged against a hard object, it mat cause temporary ulnar nerve damage. This may result in painful tingling sensations along ulnar aspect of forearm and hand. Because of these sensations, this area of elbow is called ‘Funny bone/Crazy bone’
- Eye of hand: median nerve. Enables the individual to feelthinness and texture of cloth
- Pronator syndrome: compression of Median nerve between two heads of pronator teres
- Infection of pulp spaces is Felon/Whitlow
REMEMBER
USMLE Favorite
Important Nerves Involved in | |
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- The Axillary nerve is a branch of the posterior cord of the brachial plexus
It is particularly susceptible to the injury in shoulder dislocations that displace the humeral head or in fracture of the surgical neck of the humerus
A poorly placed crutch (Crutch Palsy) may also damage this nerve causing paralysis of the Teres minor and Deltoid muscles
- Arm abduction is impaired and there is associated loss of sensation over the lower half of the deltoid
- When the head of the humerus dislocates from the glenohumeral joint, it exits inferiorly, where the joint capsule is the weakest. Immediately inferior to the glenohumeral joint, the axillary nerve exits from the axilla by passing through the quadrangular space. At this location, the downward movement of the head of the humerus can stretch the axillary nerve. The axillary nerve innervates the deltoid muscle after leaving the axilla.
- The Lower Subscapular nerve innervates the Teres major, which is responsible for adducting and medially rotating the arm, it is a branch of the posterior chord (C5 C6) of the brachial plexus.
- The Suprascapular nerve innervates the Supraspinatus and Infraspinatus muscle that are responsible for abduction and lateral rotation of the arm. The nerve is derivated from the C5 and C6 nerve roots
In shoulder abduction:
Humerus elevates
Clavicle rotates
Lateral rotation of scapula occurs along with acromioclavicular joint movement.
- The Throacodorsal nerve innervates the latissimus dorsi muscle that is responsible from adduction and extension of the arm. The nerve arises from the posterior chord (C5, C6, C7) of the brachial plexus
- Musculocutaneous nerve supplies (BBC) biceps, bracialis and corocabrachialis.
- Brachioradialis is supplied by radial nerve.
Effects caused by Injuries of Important Nerves of Upper Limb
| Muscles of anterior compartment of arm Supplies Biceps, corocabrachialis, brachialis
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| Muscles of anterior compartment of forearm Injury to median nerve at wrist causes:
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| Deltoid and teres minor Injury causes
| Fracture surgical neck of humerus dislocation of shoulder |
| Posterior muscles of arm and forearm Injury causes
| Fracture of humeral shaft |
USMLE Case Scenario
Deltoid is a thick muscle. It arises from the anterior border and superior surface of the lateral third of the clavicle. Which of the following nerves innervates the deltoid?
- Radial
- Musculocutaneous
- Ulnar
- Anterior interosseous c nerve
- Cranial nerve XI
- Subscapular
- Axillary
Ans. 7. Axillary Nerve
Action of Various Muscles of Upper Limb
- Flexors of forearm: Biceps, brachialis, brachioradialis
- Extensors of arm: Triceps, Anconeus
- Muscles attached to greater tubercle: Supraspinatus, infraspinatus, teres minor
- Muscles attached to lesser tubercle: subscapularis
- Muscles attached to coracoid process: biceps, short head of biceps
- Abductors of shoulder joint: Deltoid, serratus anterior, trapezius
- Adductors of shoulder joint: pectoralis major, lattismus dorsi
Cleidocranial Dysostosis
- Defective intramembranous ossification
- Agenesis of clavicle and deformity of skull cap
Four Rotator Cuff Muscles are
Supraspinatus
Infraspinatus
Teres minor
Subscapularis
Remember: Clinical Anatomy (USMLE Favorite)
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- Triangular depression formed on the posterolateral side of the wrist and metacarpal I by the extensor tendons passing into the thumb
- Historically, ground tobacco (snuff) was placed in this depression before being inhaled into the nose
- The base of the triangle is at the wrist and the apex is directed into the thumb. The impression is most apparent when the thumb is extended:
- The lateral border is formed by the tendons of the abductor pollicis longus and extensor pollicis brevis;
- The medial border is formed by the tendon of the extensor pollicis longus;
- The floor of the impression is formed by the scaphoid and trapezium and distal ends of the tendons of the extensor carpi radialis longus and extensor carpi radialis brevis. Structures inside:
Remember essentially:
- The radial artery passes obliquely through the anatomical snuffbox
- Terminal parts of the superficial branch of the radial nerve pass subcutaneously over the snuffbox
- Origin of the cephalic vein from the dorsal venous arch of the hand
Volkmans Ischemic Contracture (Features) (P)
- Pallor
- Pain (Most important sign)
- Paralysis
- Parasthesias
- Pulselessness
Median nerve mostly involved with Deformity: Flexion of wrist, Extension of Fingers at MCP, Flexion at IP and Pronation of forearm. Flexor digitorum profundus and Flexor Pollicis Longus are muscles damaged.
Dupuytrens contracture
Progressive, Painless, Puckeringor fibrosis of skin of Palmar Fascia with flexion of MCP joints of ring and little fingers
Colles Fracture
- Fall on outstretched hands, Common in elderly women
- Distal fragment displaced dorsally, Angulated dorsally, supinated and is also called as ‘Dinner Fork’ Deformity
De Quervain syndrome
Also known as washerwoman’s sprain or mother’s wrist is a tendinosis of the sheath or tunnel that surrounds two tendons that control movement of the thumb. (Extensor pollicis brevis and abductor pollicis longus muscles). De Quervain is potentially more common in women; the speculative rationale for this is that women have a greater styloid process angle of the radius. Symptoms are pain, tenderness, and swelling over the thumb side of the wrist, and difficulty gripping. Finkelstein’s test is used to diagnose de Quervain syndrome in people who have wrist pain.
Scaphoid Fracture
Scaphoid is one of the Carpal bones which undergo fracture commonly as well as avascular necrosis. Avascular necrosis of ‘proximal’ fragment is seen
Injury occurs by fall on outstretched hands. MC site of injury is ‘Waist’
Tenderness in ‘Anatomical snuff box’ maybe seen. Best Radiological view is Oblique view
In absence of Radiological findings, suspect scaphoid fracture. Most common site is between proximal 1/3 and distal 2/3.
Hip joint
- Medial rotator of thigh:Gracilis
- Lateral rotators of femur are:Obturator internus, Obturator externusSartorius, Pyriformis
Superior gemellus, inferior gemellus
- Abductors of the hip include the gluteus medius and gluteus maximus
- Adductors of the hip include the adductors longus, brevis and magnus
- Extensors of hip include gluteus maximus
- Internal (medial) rotators of the hip include gluteus medius, minimus, Tensor facia lata
- Lateral rotators: quadriceps femoris (rectus femoris, vastus lateralis, medialis and intermedius)
- Iliopsoas is flexor of hip
Remember:
- Tensor fascia lata is extensor of knee, Abductor and medial rotator of hip. (Imp) TEAM
- Ilio tibial tract is flexor, external rotator, abductor of hip. (Imp)
Knee Joint
- Extensor of knee: quadriceps femoris
- Flexion of knee: long head of biceps femoris. Semimembranosus, semitendonosus, ischial head of adductor magnus
- Medial rotation: Semimembranosus, semitendonosus, popliteus
- Lateral rotation: biceps femoris
Important Points: (USMLE Favorite)
- Meralgia Parasthetica Lateral cutaneous nerve of thigh
- Anterior Tarsal Tunnel Syndrome: Deep peroneal nerve
- Tarsal Tunnel syndrome: Tibial nerve
- Joggers Foot: Medial plantar nerve
- Hip Pointer: Iliac Crest
- Tennis Leg: Gastrocnemius Soleus strain
Hip Joint
- Ileo femoral ligament is ligament of Bigelow
- It is the strongest ligament
- It prevents hyperextension of hip
- Pain of hip is referred to knee joint
Knee
- Coronary ligament is present between menisci and tibial condyle
- There is other Coronary ligament in liver
- Posterior dislocation of Femur is prevented by anterior cruciate ligament
- Posterior cruciate ligament prevents posterior dislocation of Tibia
- Ligament of Humphery and Wrisberg are anterior and posterior meniscofemoral ligaments
MENISCAL TEAR
- Medial meniscus is 20 times more prone to injury than lateral meniscus. The medial meniscus is firmly adherent to the deep part of tibial collateral ligament. In forceful strains (adduction and lateral rotation of the femur over the tibia with the foot firmly placed on the ground) the medial meniscus gets torn. It is because:
- The medial collateral ligament does not allow the meniscus to move away from under the femoral condyle
- It gets compressed crushed between femoral and tibial condyles that are moving with great force
- Part of torn cartilage may get displaced. This small piece floats in the joint cavity. It may get lodged between femoral and tibial condyles causing locking of knee joint in flexed position
Arterial Supply of Hip Joint
- Obturator artery
- Medial circumflex artery
- Lateral circumflex artery
- Superior gluteal artery
- Inferior gluteal artery
In Fracture Neck of femur, Blood supply is from these vessels.
USMLE Case Scenario
A 88-year-old osteoporotic female who was a chronic smoker stumbled and fell. The right leg is shortened and externally rotated with marked loss of range of movements at hip joint
The most likely cause is: Fracture Neck of femur
Nerve Supply of Hip Joint
- Femoral nerve through nerve to rectus femoris
- Anterior division of obturator nerve
- Nerve to quadrates femoris
- Superior gluteal nerve
Arterial Supply of Knee Joint
- Genicular branches of popliteal artery
- Genicular branches of femoral artery
- Genicular branches of lateral circumflex femoral artery
- Branches of anterior tibial artery
- Branches of posterior tibial artery
Nerve Supply of Knee Joint
- Femoral nerve through nerve to vasti
- Posterior division of obturator nerve
- Sciatic nerve through tibial and common peroneal nerves
Nerves Related to Lower Limb Compartments: (USMLE Favorite)
- Adductor compartment of thigh: Obturator nerve
- Flexor compartment of thigh: Femoral nerve
- Posterior compartment of thigh (hamstrings); tibial part of sciatic nerve
- Gluteal region: superior and inferior gluteal nerves
- Anterior compartment of leg: Deep peroneal nerve
- Lateral compartment of leg: Superficial peroneal nerve
- Posterior compartment of leg: Tibial nerve
| Anterior compartment of high |
| Medial compartment of thigh |
| Posterior compartment of thigh Posterior compartment of leg |
| Short head of biceps femoris |
| Lateral compartment of leg Injury causes loss of eversion of foot |
| Anterior compartment of leg Injury causes foot drop |
Superior gluteal nerve | Gluteus minimus, gluteus medius, tensor fascia lata NOT Gluteus maximus. Injury Causes |
(Very Important) | loss of abduction of limb |
Impairment of gait Patient cannot keep pelvis level when standing on one leg. Tredlenburgs sign + | |
Inferior gluteal nerve | Gluteus maximus. Injury causes: Weakened hip flexion Difficulty rising from sitting position. |
- Q angle: Quadriceps angle is formed by line of pull of quadriceps femoris muscle and that of ligamentum patellae as they intersect at center of patella. more pronunced in females
- Genu valgum (knock knee) angle < 165°
- Genu varum (bow legs) angle > 180°
The Common Peroneal Nerve
Branches into the superficial and deep peroneal nerves, which supply the muscles of the anterior compartment of the leg and cutaneous areas of the distal anterior leg, dorsum of the foot, and most of the digit
The Tibial Nerve
Supplies all the muscles in the posterior compartment of the leg (e.g. tibialis posterior, flexor digitorum longus, gastrocnemius, and soleus)
Movements at Different Joints
- Ankle: Dorsiflexion, Plantar flexion
- Subtalar joint: Inversion, eversion
- Mid tarsal joint: Forefoot adduction and abduction
Muscles Involved in Various Movements
| Gastrocnemius, soleus |
| Tibialis anterior |
| Tibialis anterior, tibialis posterior |
| Peroneus longus, peroneus brevis |
- It is related to the neck of fibula and winds around it
- It is the smaller terminal branch of Sciatic nerve
- It pierces peroneus longus
- It divides into superficial and deep peroneal nerves and supplies the anterior and lateral compartments of leg
- Injury to CPN produces foot drop
- It is subcutaneous
- It is the most common nerve in lower limb to get injured
Ankle Joint
Dorsiflexion |
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Plantar flexion |
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Inversion |
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Eversion |
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Reflexes
| C5, C6 |
| C5, C6 |
| C5, C6 |
| C6, C7 |
| L1, L2 |
| L2, L3, L4 |
| L5 S1 |
| S1, S2 |
| S3, S4 |
Important Points about Anatomy of Breast
- The protuberant part of the human breast is generally described as overlying the 2nd to the 6th ribs, and extending from the lateral border of the sternum to the anterior axillary line. Actually, a thin layer of mammary tissue extends considerably farther from the clavicle above to the 7th or 8th ribs below, and from the midline to the edge of latissimus dorsi posteriorly.
- The Axillary tail of Spence in the breast is of considerable surgical importance. In some normal cases it is palpable, and in a few it can be seen premenstrually or during lactation. A well-developed axillary tail is sometimes mistaken for a mass of enlarged lymph nodes or a lipoma.
- 43The lobule is the basic structural unit of the mammary gland. The number and size of the lobules vary enormously: they are most numerous in young women. From 10 to over 100 lobules empty via ductules into a lactiferous duct of which there are from 15 to 20. Each lactiferous duct is lined by a spiral arrangement of contractile myoepithelial cells and is provided with a terminal ampulla — a reservoir for milk or abnormal discharges.
- The ligaments of Cooper are hollow conical projections of fibrous tissue filled with breast tissue, the apices of the cones being attached firmly to the superficial fascia and thereby to the skin overlying the breast. These ligaments account for the dimpling of the skin overlying a carcinoma.
- The areola contains involuntary muscle arranged in concentric rings as well as radially in the subcutaneous tissue. The areolar epithelium contains numerous sweat glands and sebaceous glands, the latter of which enlarge during pregnancy and serve to lubricate the nipple during lactation (Montgomery’s tubercles).
- The nipple is covered by thick skin with corrugations. Near its apex lie the orifices of the lactiferous ducts. The nipple contains smooth muscle fibers arranged concentrically and longitudinally; thus is an erectile structure which points outwards. Lymphatics of the breast drain predominantly into the axillary and internal mammary lymph nodes. The axillary nodes receive approximately 75 percent of the drainage and are arranged in the following groups.
Blood Supply is via
- Internal thoracic artery
- Intercostal artery
- Lateral thoracic artery
Lymph nodes of Breast
- Lateral, along the axillary vein
- Anterior, along the lateral thoracic vessels
- Posterior, along the subscapular vessels
- Central embedded in fat in the center of the axilla
- Interpectoral, a few nodes lying between the pectoralis major and minor muscles
- Apical, which lie above the level of the pectoralis minor tendon in continuity with the lateral nodes and receive the efferents of all the other groups
The apical nodes are also in continuity with the supraclavicular nodes and drain into the subclavian lymph trunk which enters the great veins directly or via the thoracic duct or jugular trunk. The sentinal node is that lymph node designated as the first axillary node draining the breast.
The internal mammary nodes are fewer in number and lie along the internal mammary vessels deep to the plane of the costal cartilages
Mondor’s disease is thrombophlebitis of the superficial veins of the breast and anterior chest wall (although it has also been encountered in the arm).
Familial breast cancer Recent developments in molecular genetics and the identification of a number of breast cancer predisposition genes (BRCA1, BRCA2 and TPS3). These women have a risk of developing breast cancer two to 10 times above baseline.
- Lymph nodes below Pectoralis Minor Level 1
- Lymph nodes behind Pectoralis Minor Level 2
- Lymph nodes above Pectoralis Minor Level 3
- The principal nodes which drain the breast are: Axillary Group of Lymph nodes
- About 70 -75% of lymph from breast drains into Axillary group of Lymph nodes, 20% into internal mammary group of Lymph nodes and 5% into posterior intercostal group of lymph nodes
- Among the Axillary Group Chief is the Anterior group
- Rotters nodes are interpectoral nodes
- Absence of sternal head of pectoralis major: Polands syndrome
- Vena caval opening:
- Thoracic 8 level
- Inferior vena cava
- Rt phrenic nerve
- Esophageal opening:
- Thoracic 10 level
- Esophagus
- Vagus nerves
- Esophageal branch of it gastric artery
- Aortic opening:
- Thoracic 12 level
- Aorta
- Thoracic duct
- Azygous vein
CONTENTS OF IMPORTANT STRUCTURES
Contents of Spermatic Cord: (USMLE Favorite)
- The ducts deferens
- Testicular and cremastric arteries
- Artery of vas
- The pampiniform plexus of veins
- Lymph vessels from testis
- Genital branch of Genitofemoral nerve
- Remains of processus vaginalis
Contents of Rectus Sheath: (USMLE Favorite)
- Rectus abdominis and pyramidalis muscle
- Superior epigastric artery and inferior epigastric artery
- Superior epigastric vein and inferior epigastric vein
- Lower five intercostal nerves and subcostal nerve
Contents of Broad Ligament: (USMLE Favorite)
- Uterine tube
- Round ligament of uterus, ligament of ovary
- Uterine vessels, ovarian diseases
- Uterovaginal, ovarian nerve plexus
- Epoophoron, Paroophoron
- Lymph vessels, lymph nodes
- Perianal space
- Ischiorectal space
- Lunate fascia
- Pudendal canal
Contents of Adductor Canal are: (USMLE Favorite)
- Femoral artery
- Saphanous nerve
- Nerve to vastus medialis
- Esophageal opening lies in muscular part of diaphragm
- Vena caval lies in central tendon of diaphragm
- Aortic opening is not a true opening but an osseo aponeurotic opening
- Greater and lesser splanchnic nerves pierces each crus of diaphragm
- Lt crus is also pierced by hemi azygous vein
- Sympathetic chain passes behind medial arcuate ligament
- Subcostal nerves vessels pass behind lateral arcuate ligament
- Superior epigastric vessels and lymphatics pass through Foramen of Morgagni (Larrys space)
- Musculophrenic vessels pierce the diaphragm
- Hernia does not occur through vena caval opening
- Bochaldeks hernia occurs through posterolateral part of diaphragm
- Morgagni hernia occurs anteriorly on right usually
- Remember Accessory phrenic nerve is commonly a branch from the nerve to subclavius
Sites of Esophageal Constrictions
Distance from Incisor | Landmark |
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| Pharyngoesophageal junction |
| Aortic arch crossing |
| Left bronchus |
| Pierces diaphragm |
Esophagus
- Length 25 cm
- Commences at lower end of cricoid
- Has squamous epithelium
- Toughest layer is muscularis
- No serosa
THORAX
Heart
- Right coronary artery arises from anterior aortic cusp
- Left coronary arises from posterior aortic cusp
- Posterior interventricular artery determines coronary dominance
- In case it arises from left coronary, left dominance
- Right Coronary artery mostly supplies SA node, AV node, AV bundle
- The SA node is usually supplied by Right coronary artery and Right Vagus
- The AV node is usually supplied by Right coronary artery and Left vagus
- Sympathetic innervation is by T2-T6
- Maximum (90%) of venous drainage of Heart goes to Coronary Sinus
- In fetal life left sided svc drains into coronary sinus
- Great Cardiac Vein follows Anterior Interventricular artery
- Middle Cardiac Vein follows Posterior Interventricular artery
- Small Cardiac Vein follows Rt Marginal artery
- Inferior surface of heart is formed by Rt and Lt ventricle
- Base of heart is formed by Rt and Lt atrium
- Part of heart lying close to esophagus: Lt atrium
Structures Present In:
- Musculi pectinati: Atria of heart
- Trabeculae cornea: Rt ventricle of heart
- Moderator band/Septomarginal trabeculae: right ventricle
- Coronary sinus, SVC, IVC: open in Right atrium
- SA node is located in: Rt Atrium
- Whole of conducting system is mostly supplied by rt coronary artery except Right bundle branch (supplied by left coronary artery)
- Holmes heart: single ventricle
Coronary Sinus
It is the largest venous channel of the heart about 3 cms. It located in left posterior coronary sulcus
It is a remnant of left horn of sinus venosus = while the right horn gets incorporated into right atrium
It opens into the right atrium of the heart through an orifice of coronary sinus and has a valve called the Thebesian valve. It receives:
- Great cardiac vein
- Middle cardiac vein
- Small cardiac vein
- Right marginal vein
- Oblique vein of left atrium
- Right marginal vein
Thoracic Duct
- Also called as Pecquets duct
- Beaded in appearance
- 18 inches in length
- It is the largest lymphatic pathway in body
- The duct commences in the abdomen as an elongated lymph sac of the cisterna chylli is: Thoracic duct
- Begins from cisterna chyli at the level of T12 vertebrae
- Injury to thoracic duct by trauma leads to chylothorax
Bronchopulmonary Segment
- Vascular segment
- Independent
- Bronchial artery supplies till respiratory bronchiole
- Largest subdivision of lobe
Remember
Because the right main bronchus is wider and more vertical than the left, foreign objects are more likely to be aspirated into the right main bronchus. The superior segmental bronchus of the lower lobar bronchus is the only segmental bronchus that exits from the posterior wall of the lobar bronchi. Therefore, if a patient is supine at the time of aspiration, the object is most likely to enter the superior segmental bronchus of the lower lobe.
Peculiarities of Blood Supply of Lung
- Smallest functional unit of lung is lobule
- Blood supply of lung tissue proper is by Bronchial arteries
- Bronchial arteries are branches of descending: Thoracic Aorta
- They supply nutrition to bronchial tree and pulmonary tissue up to respiratory bronchiole
- Segments distal to respiratory bronchiole are supplied by branches from pulmonary vessels
- On the right side there is only one BA arising indirectly from descending Thoracic Aorta
- On the Left side there are two BA arising directly from descending Thoracic Aorta
- Bronchial arteries are responsible for Hemoptysis
- Pulmonary arteries carry deoxygenated blood
- Pulmonary veins carry oxygenated blood
- Sequestered segments are supplied by systemic circulation
AZYGOS Lobe of Lung
- Azygos means unpaired. Azygos lobe maybe seen on the right lung
- It is seen as a result of developmental anomaly related to lung bud and posterior cardinal vein
- The posterior cardinal vein (future azygos vein) gets embedded in the substance of lung which passes as lung bud below the arch formed by posterior cardinal vein
- The part of lung medial to the vein forms the azygos lobe
GEMS ABOUT INTRA-ABDOMINAL ORGANS
The Spleen
- It is a hemolymphatic organ:
- The second largest organ of the reticuloendothelial system
- It is located in the posterior left upper quadrant of the abdomen (left hypochondrium) where its relationships to the diaphragm, stomach, pancreas, left kidney, and splenic flexure of the colon are maintained by suspensory ligaments. The splenophrenic, splenorenal, and splenocolic ligaments are usually relatively avascular and their transection allows the spleen to be displaced medially and anteriorly
- The ‘Gastrosplenic ligament’ extends from the greater curvature of the body and fundus of the stomach to the spleen, contains the short gastric arteries and veins
- The ‘Splenorenal’ ligament (Lienorenal) and attached to the spleen at the hilum: Splenic artery and vein, lymphatic structures, and often the tail of the pancreas
- The splenic vein is formed by a coalescence of polar veins in the splenic hilum and courses with the splenic artery along the dorsal surface of the pancreas to enter the portal system.
The Stomach
Starts from gastroesophageal junction to the pylorus
It is bounded on the left by the spleen and on the right by the liver
The blood supply to the stomach is extensive
- Left gastric artery, which supplies the upper lesser curvature of the stomach from celiac trunk
- The right gastric artery branches off the hepatic artery, which originates from the celiac axis; it supplies blood to the distal lesser curvature
- The left gastroepiploic artery is a branch off the short gastric vessels; it comes from the splenic and therefore originally from the celiac axis
- The right gastroepiploic artery branches off the gastroduodenal artery, which comes originally from the hepatic artery and therefore from the celiac axis
The venous drainage of the stomach empties in a variety of directions, including venous tributaries along the esophagus, veins that flow with the short gastrics to the splenic vein, and venous drainage that is carried toward the duodenum and toward the portal vein
Nerve supply is predominantly by the vagus
An anterior (left) and posterior (right) vagus nerve courses with the esophagus until the gastroesophageal junction
The ‘criminal’ nerve of Grassi is the first branch of the posterior vagal nerve innervating the greater curvature fundus. At the junction of the fundus and the antrum of the stomach, the vagal nerves branch and innervate the antrum. This vagal branch point is called the crow’s foot
The lesser sac is bounded ventrally by the stomach and is an important location during operation, in that it is a frequent space for fluid collection and is an important plane for the exposure of gastric anatomy.
Duodenum
The duodenum extends from the pylorus about 20 to 30 cm and ends at the ligament of Treitz, which is where the jejunum begins. This is marked by adhesive bands between the duodenal-jejunal junction and the retroperitoneum on the left side of the abdomen
- The duodenum is divided into four anatomic regions:
- The first portion, or the cap or bulb
- The second portion, or the descending duodenum
- The third, or transverse, portion; and the
- Fourth, or ascending, portion
Gems about Duodenum
The duodenal cap lies just beyond the pylorus. Ninety percent of ulcers occur in the duodenal cap region.
The gastroduodenal artery lies directly behind the duodenal cap, and penetrating ulcers into the pancreas initially erode through the gastroduodenal artery, accounting for the massive bleeding that occurs with these ulcers.
The second (descending) portion of the duodenum: The ampulla of Vater and the minor papilla both enter into the duodenum in this portion. The second portion of the duodenum is approximately 10 cm in length.
The third and fourth portions of the duodenum (transverse and ascending portions) are mostly retroperitoneal.
The third portion is attached to the uncinate process and crosses the abdomen and over the aorta.
Compression of the junction of the third and fourth portions of the duodenum by the angle of the SMA and the aorta is called the SMA syndrome.
49The fourth portion of the duodenum blends into the jejunum at the ligament of Treitz, which attaches this junction to the retroperitoneum. Mobilization of the ligament of Treitz is necessary in duodenal resections. The ligament is often composed of small strands of striated muscle that eventually extend to the crus of the diaphragm.
‘Kerckring’s folds’ The mucosal surface of the small intestine contains numerous circular mucosal folds called the plicae circulares (valvulae conniventes, or valves of Kerckring) of the duodenum begin just beyond the cap and continue throughout the duodenum. The concentric folds of Kerckring are approximately 1 to 2 mm thick and 2 to 4 mm high. They are taller and more numerous in the distal duodenum and proximal jejunum, becoming shorter and fewer distally.
Difference between Small and Large Intestine
Small intestine | Large intestine |
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Celiac Trunk
- LEFT GASTRIC ARTERY — Esophageal branch, gastric branch
- COMMON HEPATIC ARTERY — Right hepatic, left hepatic, Gastroduodenal artery→ supraduodenal, right gastroepiploic, superior pancreaticoduodenal artery
- SPLEENIC ARTERY — Short gastric, left gastroepiploic, pancreatic branches
Meckel’s Diverticulum
- A Meckel’s diverticulum, a true congenital diverticulum
- It is a vestigial remnant of the omphalomesenteric duct (also called the vitelline duct) and is the most frequent malformation of the gastrointestinal tract
- Meckel’s diverticulum is located in the distal ileum, usually within about 60-100 cm of the ileocecal valve
- It is typically 3-5 cm long, runs antimesenterically and has its own blood supply
- It is a remnant of the connection from the umbilical cord to the small intestine present during embryonic development
A Memory Aid is the Rule of 2’s
- 2% (of the population)
- 2 feet (from the ileocecal valve)
- 2 inches (in length)
- 2% are symptomatic
- 2 types of common ectopic tissue (gastric and pancreatic)
- Most common age at clinical presentation is 2
- Males are 2 times as likely to be affected
Anal canal above Dentate Line | Anal Canal Below Dentate Line |
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The liver
- Lies in the right upper quadrant of the abdomen
- It is the largest gland in the body, it weighs approximately 1500 gm
- The gallbladder lies on the dorsal surface of the liver in a transpyloric plane
- A peritoneal membrane (Glisson’s capsule) covers the liver
- The superior surface of the liver conforms to the undersurface of the right diaphragm. The relations of the inferior surface of the liver are the duodenum, colon, kidney, adrenal gland, esophagus, and stomach. Peritoneum invests the entire liver except for a bare area under the diaphragm on the posterosuperior surface adjacent to the inferior vena cava and hepatic vein.
Ligaments of Liver
- The falciform ligament, which attaches the liver to the anterior abdominal wall from the diaphragm to umbilicus and incorporates the ligamentum teres hepaticus
- The anterior and posterior right and left coronary ligaments, which in continuity with the falciform ligament connect the diaphragm to the liver. The lateral aspects of the anterior and posterior leaves of the coronary ligaments fuse to form the right and left triangular ligaments
- The gastrohepatic and hepatoduodenal ligaments, which consist of the anterior layer of lesser omentum and are continuous with the left triangular ligament. The hepatoduodenal ligament contains the hepatic arteries, portal vein, and extrahepatic bile ducts. It forms the anterior boundary of the epiploic foramen of Winslow and the communication between the greater and lesser peritoneal cavities.
Four Lobes of the Liver are Commonly Described
- Right
- Left
- Quadrate
- Caudate
Portal Vein
- The portal vein provides about three fourths of the liver’s blood supply
- The combination of the superior mesenteric and splenic veins forms the portal vein, behind the neck of the pancreas
- The portal vein then passes superiorly, posterior to the first part of the duodenum at the level of the second lumbar vertebra
- Portal vein is 1 to 3 cm in diameter and 5 to 8 cm in length before dividing into right and left branches at the portal hepatis
- The portal vein usually passes behind the bile duct and hepatic artery in the hepatoduodenal ligament
- The portal trunk divides into left and right hepatic branches in the portal fissure. The left branch of the portal vein is longer
- The portal vein divides into small veins and venules, which finally enter hepatic sinusoids
- The portal vein has no valves
Numerous tributaries of the portal vein connect outside the liver with the systemic venous system. Under normal circumstances these communications have little physiologic significance. However, if portal hypertension develops, these rudimentary portosystemic communications develop into large channels with increased collateral flow.
Sites of Portosystemic Anastomoses Include
- The submucosal veins of the proximal stomach and distal esophagus, which can receive blood from the coronary and short gastric veins to drain into the azygous veins (high blood flow through this pathway produces gastric varices, esophageal varices, or both)
- Umbilical and periumbilical veins, recanalized from the obliterated umbilical vein in the ligamentum teres hepaticus, and which may cause caput medusae or the loud Cruveilhier-Baumgarten bruit
- Tributaries of the inferior mesenteric vein, which include the superior hemorrhoidal veins that communicate with the middle and inferior hemorrhoidal veins of the systemic circulation and may cause large hemorrhoids; and
- Other retroperitoneal communications, including connections to the renal and adrenal veins.
Sphincter of Oddi
The circular smooth muscle fibers in the ampulla of Vater area constitute the sphincter of Oddi, which regulates the flow of bile from the liver into the duodenum
The three principal parts of the sphincter of Oddi are:
- The sphincter of the choledochus (i.e. the circular muscle fibers surrounding the intramural and submucosal bile duct);
- The pancreatic sphincter, which consists of a muscular septum between the bile and pancreatic ducts;
- Ampullary sphincter: The ampullary sphincter, the most important component of the sphincter of Oddi, includes a layer of longitudinal muscle fibers that help prevent reflux of intestinal contents into the ampullaRelaxation of the ampullary sphincter may promote reflux into the pancreatic duct.
Gallbladder
The gallbladder, a pear-shaped (pyriform), distensible appendage of the extrahepatic biliary system
Capacity: 30 to 50 ml of bile
Parts: It has a fundus, body, and neck
The duct of gallbladder cystic duct varies in length and usually contains spiral valves of Heister that regulate bile flow
Enlargement of the neck of the gallbladder such as from a stone may form a pouch (Hartmann’s pouch)
The triangle bounded by the cystic duct, common hepatic duct, and inferior border of the liver is the Triangle of Calot
The gallbladder receives its blood supply from the cystic artery, which originates from the right hepatic artery
Venous drainage of the gallbladder enters principally into the portal vein
The lymphatics drain into cystic duct nodes near the superior aspect of the cystic duct. (Cystic Lymph node of Lund)
The Triangle of Calot
It is a surgical landmark used to identify important structures during cholecystectomy, is bounded by the cystic duct, the common hepatic duct, and the inferior border of the liver
The right hepatic and cystic arteries are located within it and anomalous structures often pass through it
Moynihans Hump: An abnormal bend in the course of the right hepatic artery, throwing it into the configuration of a caterpillar hump, (Moynihan’s hump) invites injury unless it is carefully dissected free
- It is a retroperitoneal organ, lying posterior to the stomach and lesser omentum
- It extends from the duodenal C loop to the hilum of the spleen
- The gland has a distinctive yellow/tan/pink color and is multilobulated
- The gland is divided into four portions:
- The head (which includes the uncinate process)
- The neck
- The body and
- The tail
- The head of the gland extends to the right of the neck, lying within the confines of the duodenal C loop; it includes the posteroinferior extension arising from the ventral primordium, designated the uncinate process. The uncinate process extends posterior to the superior mesenteric vein, ending at the right margin of the superior mesenteric artery. The body of the pancreas lies immediately to the left of the neck; the tail of the pancreas extends to the left of the body into the splenic hilum.
- The head of the pancreas is intimately associated with the second portion of the duodenum, and these two structures are jointly supplied by two arterial arcades known as the anterior and posterior pancreaticoduodenal arteries. These arteries originate from the superior and inferior pancreaticoduodenal vessels as branches of the celiac axis and superior mesenteric artery, respectively. The distal body and tail of the pancreas are supplied by short branches of the splenic and left gastroepiploic arteries. Within the posterosuperior and posteroinferior aspects of the body of the pancreas lie the superior and inferior pancreatic arteries, respectively.
- Veins draining the pancreatic parenchyma eventually terminate in the portal vein, which arises posterior to the neck of the pancreas at the junction of the splenic and superior mesenteric veins
Multiple lymph node groups drain the pancreas
- From the head of the gland, nodes in the pancreaticoduodenal groove communicate with subpyloric, portal, mesocolic, mesenteric, and aortocaval nodes
- Lymphatics in the body and tail of the pancreas drain to retroperitoneal nodes in the splenic hilum or to celiac, aortocaval, mesocolic or mesenteric nodes
The Kidneys
- Bean shaped
- Retroperitoneal
- Right kidney is lower than left (but right suprarenal is higher than left.)
- Each kidney is 9 to 15 cm long, 4 to 5 cm wide and approximately 3 cm thick. They are located on each side of the vertebral column between the parietal perineum and the fascia and musculature of the posterior abdominal wall and are embedded in a variable amount of fat and surrounded by a layer of fascia (Gerota’s fascia)
- They lie on the side of the psoas muscle
- They are not parallel, with the upper poles being approximately 2 cm from the midline and the lower poles approximately 3.5 cm from the midline
- Coverings of Kidney (From inside to out)
- Fibrous capsule
- Perinephric fat
- Renal fascia with 2 layers
- Anterior layer of Toldts Fascia
- Posterior layer of fascia of Zuckerkandl
- Pararenal Fat
- 3 parts of diaphragm: Medial arcuate ligament, Lateral arcuate ligament, Diaphragm
- 3 muscles: Psoas major, quadrates lumborum, transverses abdominis
- 3 nerves: Subcostal, iliohypogastric, ilioinguinal nerves
- Right kidney: 12th rib
- Left kidney: 11th and 12th rib
Ureter
- 25 cm long (PGI)
- Totally retroperitoneal
- It enters true pelvis after crossing iliac vessel
Important Points about Ureter
- Starts at the hilum
- Changes its direction at the ischial spine
- Penetrates the bladder wall without any valve
- Enters the bladder at the lateral angle of the trigone
- Enters pelvis in front of bifurcation of common iliac artery
The Suprarenals or the Adrenal Glands
- Are bilateral retroperitoneal organs located on the superior medial aspect of the upper pole of each kidney
- Each gland weighs approximately 4 gm. The left adrenal is larger and flatter
- The normal adrenal cortex is bright yellow and thicker than the red-brown medulla.
Blood Supply of Suprarenals
- Superior suprarenal artery: branch of inferior phrenic artery
- Middle suprarenal artery: branch of abdominal aorta
- Inferior suprarenal artery: branch of renal artery
Venous Drainage
The left adrenal vein empties primarily into the left renal vein but may occasionally drain directly to the vena cava
Lymphatic plexuses within the subcapsular portion of the adrenal cortex and the adrenal medulla drain to the adjacent para-aortic subdiaphragmatic and renal lymph nodes.
Important Anatomical Relations
Relations at hilum of kidney (Anterior to Posterior) ‘VAP’
- Renal vein
- Renal artery
- Renal pelvis
Relations at Femoral Triangle (From Medial to Lateral) 'VAN’
- Femoral vein
- Femoral artery
- Femoral nerve
- Intercostal vein
- Intercostal artery
- Intercostal nerve
Cubital Fossa (From Medial to lateral side). ‘MBBR’
- Median nerve (Medial aspect)
- Brachial artery
- Biceps tendon
- Radial nerve
- Lateral boundary by brachioradialis muscle.
MALE REPRODUCTIVE TRACT
Testes
- It is male gonad
- Two oval structures are average 4 to 5 cm in length and 2.5 to 3.5 cm in width in the normal adult male
- 10–15 gms in weight (Indians average)
- Testis arises from the genital ridge
Covered by
- Tunica vaginalis
- Tunica albugenia
- Tunica vasculosa
- Blood supply is by testicular artery which is a branch of abdominal aorta
- Venous drainage of the testis is through the pampiniform plexus to the spermatic vein, which is usually single and emerges from the upper end of the cord and then follows the internal spermatic artery through the retroperitoneum. On the right the spermatic vein empties into the vena cava below the right renal vein, whereas on the left the spermatic vein empties into the main renal vein. Increased hydrostatic pressure, particularly on the left, may result in dilatation of the pampiniform venous plexus, producing a varicocele
- The lymphatic drainage of the testis is through the spermatic cord and the inguinal canal and then to the common iliac and preaortic and paraortic nodes, with the latter communicating across the midline at the level of the kidneys and also with the mediastinal and supraclavicular chains
- Histologically, there are two principal portions of the testis: The seminiferous tubules, which are responsible along with the Sertoli cells for spermatogenesis, and the interstitial or Leydig cells, which elaborate androgenic hormones, predominantly testosterone
Testicular Descent
- Iliac Fossa: 3rd month
- Deep Inguinal Ring: 7th month
- Pass through Inguinal Canal: 7th month
- At Superficial Inguinal ring: 8th month
- Enter Scrotum: 9th month
Are coiled structures each containing a single epididymal tubule 12 to 19 feet long and attached to the posterolateral surface of each testis
Remember:
From the tails of the epididymi sperm are transmitted into the vasa deferentia, which are direct continuations of the duct of the epididymi passing up the spermatic cord, across the inguinal canal, and then retroperitoneally to the ampulla of the seminal vesicles, with which they conjoin to form an ejaculatory duct on each side. The ejaculatory duct then empties directly into the prostatic urethra.
The principal blood supply for the epididymis is from the internal spermatic artery. Venous drainage corresponds to the arterial supply, and the lymphatic drainage of the epididymis parallels that of the testis. The prime function of the epididymis is not only as a conduit for spermatozoa but also for biochemical and functional maturation and ultimate storage.
Ductus deferens/Vas Deferens
It is 18 inches in length. The vas deferens is an easily discernible structure within the scrotum and spermatic cord because it is a heavily muscled tubular structure
Spermatic Cord
The spermatic cord, suspending each testis and its attached epididymis, is composed of the vas deferens, the internal spermatic artery, the external spermatic artery, the pampiniform plexus of veins, the lymphatic drainage system of the contents of the scrotum, and the autonomic nerve supply to the testis. In addition, the cord is surrounded by fibers of the cremasteric muscle, which assist by contraction and relaxation in the maintenance of optimal testicular temperature and provide for testicular retraction with sexual excitation or in the primitive fright reaction.
Contents of Spermatic Cord
- The ducts deferens
- Testicular and cremastric arteries
- Artery of vas
- The pampiniform plexus of veins
- Lymph vessels from testis
- Genital branch of genitofemoral nerve
- Remains of processus vaginalis
Scrotum
- The scrotal sac, consisting of two lateral compartments fused in the midline encloses the testes, epididymi, and terminal portions of the spermatic cords. The dartos, consisting of elastic fibers, connective tissue, and smooth muscle fibers, is attached to the corrugated skin of the scrotum, rich in sebaceous glands, and provides for muscular contraction of the scrotal sac in response to temperature changes or sexual excitation. The principal function of the scrotum is to aid in temperature control of the testes for optimal spermatogenesis, which takes place at temperatures several degrees lower than those in the intra-abdominal cavity
- The blood supply of the scrotum comes from the deep pudendal branches of the femoral artery and branches of the internal pudendal artery
- The lymphatics of the scrotal halves anastomose freely, surround the penis, and drain to the inguinal and femoral nodes. There are no connections between the lymphatics of the scrotum and the testes; the scrotal lymphatics do not accompany the pudendal vessels.
Seminal Vesicles
- Are paired, monotubular, convoluted structures lying beneath the base of the bladder and trigone. Posteriorly they are invested by Denonvilliers’ fascia, which separates them from the anterior wall of the rectum
- The two seminal vesicles fuse immediately with the ampullae of the vasa, forming the ejaculatory ducts, which open into the prostatic urethra at the level of the verumontanum. The seminal vesicles secrete a mucoid vehicle for the spermatozoa and also elaborate the body’s only source of fructose, which is used as an essential nutrient for maintenance of spermatozoal viability.
- It is a fibromuscular, glandular organ that surrounds the neck of the urinary bladder and the proximal portion of the male urethra. The gland is supported anteriorly by the puboprostatic ligaments, inferiorly by the genitourinary diaphragm (external urinary sphincter), and posteriorly by the rectal wall, which is separated from the prostate by an obliterated pelvic reflection of the peritoneum called Denonvilliers’ fascia.
- The prostate consisting of two portions: an anterior (inner) group of glands intimately associated with the urethra and a posterior (outer) portion of more fibromuscular character
- Arterial supply: The inferior vesical and internal pudendal arteries provide the blood supply to the prostate, entering the gland posterolaterally at the vesical neck
- Venous drainage of the prostate is complex and diffuse, with plexuses over the anterior and lateral portions of the gland that drain into the internal iliac veins
- Intercommunicating lymphatics of the prostate, bladder, seminal vesicles, vasa deferentia, and rectum provide drainage into both the internal and external iliac systems as well as the sacral promontory nodes
- Zones of Prostate:
- These zones have physiologic and surgical significance because Benign enlargement of the prostate (BHP) occurs in the transition or periurethral zone and Malignancy develops in the majority of cases in the Peripheral zone.
Urethra
18-20 cms in length with 3 parts
- Prostatic (3 cms semilunar)
- Membranous (2 cms stellate)
- Spongy/penile (15 cms slit shaped)
Prostatic part is widest and more dilatable part
Contains:
- Veru montanum (urethral crest)
- Colliculus seminalis
- Prostatic sinuses
- Prostatic utricle (analogous to uterus/vagina of females)
Cowper’s Glands: (Bulbourethral glands of Cowper) are small, paired glands lying between the layers of the urogenital diaphragm at the junction of the bulbous and membranous portions of the urethra. The ducts of the glands empty distally into the bulbous urethra traversing the corpus spongiosum. The secretions from this gland not only act as a lubricant but may also have factors that aid in seminal fluid coagulation after ejaculation.
Penile Tissue
- Organ of copulation and excretion of urine
- It consists of two parallel erectile tissues as the corpora cavernosa, which are situated dorsolaterally, and the corpus spongiosum, which invests the urethra ventrally, terminating distally in the erectile glans penis
- Each corpus cavernosum and the corpus spongiosum are enveloped in fascial sheaths, and all three corpora are surrounded by Buck’s fascia
- The blood supply of the penis is through the dorsal arteries derived from the internal pudendal arteries, which are branches of the internal iliac artery
- The venous drainage is through the dorsal veins, with the superficial dorsal vein emptying into the saphenous vein, and the deep dorsal vein emptying into the prostatic plexus known as the plexus of Santorini
- Penile erection is induced by the engorgement of the erectile tissues of the corpora, principally the corpora cavernosa
- Lymphatic drainage of the penis is abundant. The lymphatics from the shaft of the penis, the corpora cavernosa, and the skin pass through the superficial and deep inguinal nodes, communicating with the iliac nodes.
- The skin of the penis differs considerably from other skin of the body in its paucity of sebaceous glands, its elasticity, and its extensive blood supply.
REMEMBER
High Yield Points
- The bulbourethral glands secrete mucus for lubrication
- The epididymis concentrates and stores sperm for ejaculation
- The prostate gland secretes alkaline fluid to neutralize vaginal pH and induces clotting of the semen
- The seminal vesicles produce fructose, citric acid, prostaglandins, and fibrinogen. These comprise about 60% of the volume of semen
- The ampulla is the end of the vas deferens
- The bulbourethral glands secrete mucus for lubrication
- The epididymis concentrates and stores sperm for ejaculation
- The prostate gland secretes alkaline fluid to neutralize vaginal pH and induces clotting of the semen
The seminal vesicles produce fructose, citric acid, prostaglandins, and fibrinogen. These comprise about 60% of the volume of semen.
FEMALE REPRODUCTIVE TRACT
The Vagina
The vagina is a female copulatory organ. It is a muscular tube lined with stratified squamous epithelium. The adult vagina measures 12 to 13 cm in-depth. In virgin lower end of vagina is closed partially by annular fold of mucus membrane called hymen which gets distorted after intercourse forming rounded elevations called caruncle hymenale.
The Cervix
- It is the lower cylindrical portion of the uterus
- The cervix, is a fibromuscular organ covered with stratified squamous epithelium. The walls of cervix show mucosal folds called arbor vitae
- The squamocolumnar junction is the most common site of origin of squamous cell carcinoma
- The endocervical canal is lined by columnar epithelium, and racemose glands, lined with similar epithelium, are found in the fibromuscular stroma. Such glands, if obstructed, may form nabothian cysts on the cervical surface
- The nulliparous cervical os is round.
The Uterus
- The uterus is a hollow, fibromuscular-walled organ between the bladder
- The normal position of uterus is anteverted and anteflexed
- Angle of anteversion is 90°
- Angle of anteflexion is 120°
- The organ is pear shaped and in nonpregnant women measures approximately 8 cm in length and weighs 30 to 100 gm
- The fallopian tubes and the cervical canal communicate with the uterine cavity, which is lined by the endometrium
- The uterine fundus is covered by peritoneum except in the lower anterior portion, where the bladder is contiguous with the lower uterine segment and the peritoneum is reflected, and laterally where the folds of the broad ligament are attached. The uterus is supported by condensations of endopelvic fascia and fibromuscular tissue laterally at the base of the broad ligaments
Blood supply of uterus is by uterine artery which is tortuous and branch of anterior division of internal iliac artery lying on the lateral aspect of uterus in the broad ligament.
- Occurs when the uterus and its adjoining structures herniate through the vaginal canal
- Prolapse is described as first, second, or third degree in severity, the last being protrusion of the entire uterus from the vagina, with the entire vagina everted as a consequence.
- Although congenital weakness of the supporting tissues may occasionally cause uterine prolapse, the most frequent cause is childbirth. The signs of uterine prolapse are protrusion of the cervix or uterus through the introitus. Prolapse is frequently associated with cystocele or rectocele, and these defects may cause presenting symptoms. Symptoms include backache, significant pelvic pressure, and ulceration or bleeding of the prolapsed structures.
The Fallopian Tubes
Tortous ducts about 10 cms in length:
- Arise from the superior portion of the lateral borders of the uterus, superior to the attachment of the round ligaments, and are patent. The distal ends, the fimbriae, open into the abdominal cavity and the proximal ends open into the uterine cavity. It is divided into interstitial, isthmic, ampullar, and fimbriated portions
- The wall is thin with two muscular layers and an outer layer of peritoneum within the upper borders of the broad ligament.
The Ovaries
Lie in the ovarian fossa. Ovaries are almond-shaped structure measuring 2 × 3 × 3 cm and is located on the posterior surface of the broad ligament and inferior to the fallopian tube. The ovary has a cortex and a medulla. Germinal epithelium, a single layer of cuboidal cells, covers condensed fibrous tissue called the tunica albuginea. Follicles originate within the ovarian cortex and are composed of the basic embryonic complement; no new follicles are formed after birth
Mesovarium is a fold of peritoneum by which ovary is connected to the broad ligament
The Arterial blood supply is predominantly by ovarian artery a branch of Abdominal aorta
Venous drainage is by Pampiniform plexus. The left ovarian vein empties into the left renal vein; the right ovarian vein empties into the vena cava just inferior to the renal vein.
The Adult Inguinal Canal
- It is approximately 4 cm in length
- Extends between the internal (deep inguinal) ring and the external (superficial inguinal) ring opening
- The inguinal canal contains either the spermatic cord or the round ligament of the uterus
- The inguinal canal is bounded superficially by the external oblique aponeurosis
- The superior wall is composed of internal oblique muscle, transversus abdominis muscle, and the aponeuroses of these muscles
- The inferior wall of the inguinal canal is formed by the inguinal ligament and lacunar ligament
- The posterior wall (floor) of the inguinal canal is formed by the transversalis fascia and the aponeurosis of the transversus abdominis muscle
- Hesselbach’s triangle: The inferior epigastric vessels serve as the superolateral border of Hesselbach’s triangle. The medial border of the triangle is formed by the rectus sheath, and the inguinal ligament serves as its inferior border
- Hernias occurring within Hesselbach’s triangle are considered direct hernias, whereas hernias occurring lateral to the triangle are indirect hernias.
THE HEAD AND NECK AND CNS
The Scalp
The SCALP has five layers:
- S – Skin
- C – Connective tissue
- L – Loose connective tissue
- P – Pericranium
The scalp receives a rich vascular supply. This arises from both the external and internal carotid arteries with the vessels lying in the dense connective tissue layer.
The anterior part of the scalp is supplied by the supratrochlear and supraorbital arteries, and branches of the internal carotid via the ophthalmic artery
The lateral and posterior part of the scalp is supplied by the superficial temporal, posterior auricular and occipital arteries, and branches of the external carotid
The sensory nerves run with the arteries and are derived from the trigeminal nerve at the front and sides
The posterior aspect is supplied by the greater and lesser occipital nerves with motor supply to the occipitofrontalis muscle by the facial nerve
Venous drainage of the face and anterior scalp is via the facial vein. The lateral and posterior aspects are drained by the external jugular vein and the vertebral venous plexus, respectively. The veins of the scalp and face communicate directly with the intracranial venous sinuses via emissary veins, hence infections in the nasal region have the potential to cause cavernous sinus thrombosis
Lymph drainage from the scalp is to the preauricular and occipital lymph nodes
The loose areolar tissue under the galea aponeurotica is a ‘Dangerous zone for infections‘. Pus can spread freely in this layer and reach the intracranial sinuses through the emissary veins
Abscesses and hematomas under the pericranium are limited to the area of one bone because the pericranium is firmly adherent to the sutures between the skull bones
Osteomyelitis of the skull is associated with a subperiosteal swelling and edema of the scalp referred to as Port’s puffy tumor
Fractures of Facial Skeleton
The Le Fort I fracture separates the alveolus and palate from the facial skeleton above
The fracture line runs through points of weakness from the pyriform aperture, through the lateral and medial wall of the maxillary sinus running posteriorly to include the lower part of the pterygoid plates
The Le Fort II fracture is pyramidal in shape. The fracture involves the orbit, running through the bridge of the nose, and the ethmoids whose cribriform plate maybe fractured, leading to a dural tear and CSF leak. It continues to the medial part of the infraorbital rim, through the infraorbital foramen and through the infraorbital fissure. The orbital floor is always involved
The Le Fort III fracture effectively separates the facial skeleton from the base of the skull — The fracture lines run high through the nasal bridge, septum and ethmoids, again with the potential for dural tear and CSF leak, and irregularly through the bones of the orbit to the frontozygomatic suture. The zygomatic arch fractures, and the facial skeleton is separated from the bones above at a high level through the lateral wall of the maxillary sinus and the pterygoid plates.
Various Important Areas of Cerebrum
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Important Points about Functional Anatomy of Cerebral Cortex
Frontal lobe | Precentral cortex (Post Part) | Primary motor area | Area 4 – center for movement |
(concerned with initiation of voluntary movements and speech) | Area 4S – suppressor area. Inhibits movements initiated by area 4. | ||
Premotor area | Area 6 – concerned with coordination of movements initiated by area 4. | ||
Area 8 – frontal eye field. | |||
Area 44 and 45 (broca’s area) – motor area for speech. | |||
Supplementary motor area | Concerned with coordinated skilled movements. | ||
Prefrontal cortex (Ant Part) | Silent area or association area Center for higher functions – emotion, learning, memory | Area – 9 to 14, 23, 24, 29 and 32. Center for planned action Seat of intelligence. Personality of individual | |
Area 1 – concerned with sensory perception | |||
Parizetal lobe | Somesthetic area I | Area 2 and 3 – integration of these sensations. Spatial recognition. Recognition of intensity, similarities and diff. B/W stimuli | |
Somesthetic area II | Concerned with perception of sensation. | ||
Somesthetic association area | Synthesis of various sensations perceived by S. Area-I. Stereognosis | ||
Temporal lobe | Primary auditory area | Area 41, 42 and wernicke’s area – concerned with perception of auditory impulses, analysis of pitch, determination of intensity and source of sound Superior part of temporal gyrus. | |
Auditopsychic area | Area 22 – Interpretation of auditory sensation | ||
Area of equilibrium | Maintenance of equilibrium | ||
Occipital lobe | Primary visual area | Area 17 – Perception of visual impulse Lines of Gernari seen. | |
Visual association area | Area 18 - Interpretation of visual impulses | ||
Occipital eye field | Area 19 - Movements of eye |
Lemniscus, tract and sensation | Thalamic nucleus | Part of the internal capsule | Sensory areas of the cerebral cortex |
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Medial lemniscus (Proprioception and fine touch) | PLVNT | SENSORY RADIATION | Upper 1/3 of sensory area in post-central gyrus (Arm and leg region). |
Spinal lemniscus (Pain, temperature and crude touch) | |||
Trigeminal lemniscus (Pain, temperature, touch and proprioception from the «head», taste) | PMVNT | In posterior ½ of postlimb of internal capsule (IC) | Lower 1/3 of sensory area in post-central gyrus (Face region). |
Lateral lemniscus (hearing) | Medial geniculate body [MGB] | AUDITORY RADIATION in sublentiform part of IC | Auditory area in Heschl’s gyrus in temporal lobe (area 41 and 42). |
Internal Capsule
Part of internal capsule | Types of fibers in it |
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A small lesion at the level of internal capsule can result in a clinical scenario with widespread manifestations and most of them lethal depending on what part of internal capsule is damaged.
The internal capsule maybe damaged by a cerebrovascular lesion mostly by Hemorrhage (rupture of Charcots artery) leading to Hemiplegia on the opposite side of the body.
In this type of Hemiplegia motor functions are effected mostly and sensory functions later or not at all because motor fibers lie laterally and the arterial supply is more laterally as a result of which are motor fibers likely to be effected more.
Summary of the Lesion in Brown Sequard Syndrome
On the «same» side of the lesion
- Pyramidal tract damage results in: UMNL and motor paralysis below the injury (spastic paralysis, hyperactive reflexes, loss of superficial reflexes and Babinski sign)
- Proprioceptive tracts damage (gracile and cuneate) results in: loss of sense of position, sense of passive movement, sense of vibration and touch discrimination below the injury. These are the signs of sensory ataxia.
On the «opposite» side of the lesion:
- Lateral spinothalamic tract damage results in: loss of pain and temperature sensation beginning one or two dermatomes below the lesion
- Ventral spinothalamic tract damage results in: little or No change in the sense of simple touch.
Remember
Midbrain: Usually the fibers of the third (oculomotor) nerve are affected — alternating oculomotor hemiplegia, this means;
Hemiplegia on opposite half of the body (UMNL)
Signs of oculomotor nerve paralysis on the same side (LMNL)
Pons: Usually the fibers of the sixth (abducent) nerve are affected — alternating abducent hemiplegia, this means:
Hemiplegia on opposite half of the body (UMNL)
Signs of abducent nerve paralysis on the same side (LMN)
Medulla: Usually the fibers of the hypoglossal nerve are affected — alternating hypoglossal hemiplegia, this means
Hemiplegia on opposite half of the body (UMNL)
Signs of hypoglossal nerve paralysis on the same side (LMNL)
Arterial Territories and Important Points in Blood Supply of Brain
- Left middle cerebral artery: Blockage of this vessel would cause, among other effects, right-sided hemiplegia and sensory deficits mainly of the face and arms, a right visual field defect with inability to gaze to the right, and aphasia.
- Left anterior cerebral artery: This vessel supplies the medial aspects of the left hemisphere. Blockage may cause a weak, numb right leg (and possibly arm symptoms in milder forms). The face is typically spared.
- Right anterior cerebral artery: This vessel supplies the medial aspects of the right hemisphere. Blockage may cause a weak, numb left leg (and possibly arm symptoms in milder forms). The face is typically spared.
- Left posterior cerebral artery: This lesion presents as a right-sided visual field deficit, alexia without agraphia (if the corpus callosum is spared), and possible defects in naming colors.
- Right posterior cerebral artery: This lesion typically presents as a left-sided visual field deficit along with left-sided sensory loss if the thalamus is affected. There may also be left-sided neglect
- Visual cortex is supplied by posterior + middle cerebral artery.
- Left posterior inferior cerebellar artery: This lesion would cause infarction of the lateral medulla and inferior cerebellar surface, causing vertigo with vomiting, dysphagia, and dysarthria. In addition, there would be nystagmus looking toward the left, left–sided Horner’s syndrome, and loss of pinprick sensation on the left side of the face and on the right side of the trunk and extremities. This condition is also known as Wallenberg’s syndrome.
- Right posterior inferior cerebellar artery: This lesion would cause infarction of the lateral medulla and inferior cerebellar surface, causing vertigo with vomiting, dysphagia, and dysarthria. In addition, there would be nystagmus looking toward the right, right–sided Horner’s syndrome, and loss of pinprick sensation on the right side of the face and on the left side of the trunk and extremities. This condition is also known as Wallenberg’s syndrome.
Cranial Nerves: (USMLE Favorite)
- Optic nerve is not only a cranial nerve. It is a tract and direct extension of CNS
- This nerve is about 4 cm long
- The optic nerve is enclosed in 3 sheaths covering with meninges
- It is crossed by ophthalmic artery
- Trigeminal nerve is the largest cranial nerve
- Abducent nerve has the longest course
- Trochlear nerve has the longest intracranial course. Thinnest as well
- Cranial nerve 3 and 4 have their nuclei in midbrain
- Cranial nerve 5, 6, 7, 8 have their nuclei in pons
- Cranial nerve 9, 10, 11, 12 have their nuclei in medulla
- Cranial nerve emerging from dorsal aspect of brain: Trochlear
- MC nerve involved in intracranial aneurysms: Occulomotor
- Common nucleus for VII, IX, X nerves is Nucleus Tractus Solitarius. (NTS)
- Trochlear nerve has the longest intracranial course
Summary of Distribution of Cranial Nerves: (USMLE Favorite)
No. | Nerve | Type | Function |
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1. | Olfactory | Sensory | smell |
2. | Optic | Sensory | vision |
3. | Oculomotor | Motor | To all muscles of the eye except two: (superior oblique and lateral rectus) |
4. | Trochlear | Motor | To one eye muscle (superior oblique) |
5. | Trigeminal | Mixed mainly sensory with small motor part | Sensory to
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6. | Abducent | Motor | To one eye muscle (lateral rectus) |
7. | Facial | Mixed Motor ———Sensory Parasympathetic |
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8. | Vestibulocochlear | Sensory |
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9. | Glossopharyngeal | Mixed Motor ———Sensory Parasympathetic |
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10. | Vagus (Including Cranial accessory) | Mixed Motor ———Sensory Parasympathetic |
Parasympathetic and sensory to: The structures in the thorax and abdomen |
11. | Spinal Accessory | Motor | To two important muscles of the neck:
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12 | Hypoglossal | Motor | To all muscles of the tongue (except one) |
The First (Olfactory) Nerve Palsy
The chief function of the 1st cranial nerve (olfactory nerve) is concerned with the sense of smell. Cells of origin are located in the nasal mucosa. Nerve filaments group and pass through the cranium at cribriform plate and end in olfactory bulb. The olfactory nerve is composed exclusively of somatic afferent fibers.
The olfactory nerve branches penetrate through the cribriform plate, and collect in the olfactory bulb and nerve which passes under the frontal lobe to the temporal lobe and other centers
EXAMINATION
Each nostril is examined separately. One nostril is closed while the patient sniffs with the other. Mild aromatic substances such as orange, coffee, or tobacco should be used as strong irritant smells stimulate the sensory endings of the fifth nerve. The result of affection will be loss of smell or anosmia.
The Third (Oculomotor) Nerve Palsy
It supplies all extraocular muscles except the superior oblique and the lateral rectus
Complete paralysis results in:
- External ophthalmoplegia: In a complete lesion inability to move the eye upward, inward and downward
- External Squint: The eye is deviated laterally and downwards due to the unopposed action of the lateral rectus and superior oblique
- Diplopia: A person sees double
- Ptosis: Drooping of the upper eyelids due to paralysis of levator palpabrea superioris
- Dilated nonreactive pupil due to paralysis of the sphincter pupillae. The pupil also shows no reaction to light (direct or consensual), or to accommodation.
The Fourth (Trochlear) Nerve Palsy
- There is weakness or paralysis of the superior oblique muscle which normally moves the eye downwards and inwards
- Result: Defective depression of the adducted eye. The patient is unable to look at his shoulder
- Symptom presentation: DIPLOPIA (double vision), when looking downwards, e.g. when reading or descending the stairs. The head may tilt to the opposite side to minimize the diplopia.
The Sixth (Abducent) Nerve Palsy
The sixth nerve supplies the lateral rectus which normally rotates the eye laterally. Its paralysis causes:
- Internal Squint: The eyeball is turned inwards due to unopposed adduction of the medial rectus
- Diplopia, which is maximum on looking outwards.
The Fifth (Trigeminal) Nerve Palsy
The sensory fibers are divided into three divisions:
- Ophthalmic Division
- Maxillary Division
- Mandibular Division
Sensation
Sensation is tested in the distribution of the 3 divisions of the nerve. Routinely, it is sufficient to test the sensation at three Sites: on the forehead, the cheek and over the lower jaw, together with anterior two-thirds of the tongue
Motor Functions
A. Masseters And Temporalis:
- Any wasting of the temporalis
- The degree of contraction of the temporalis and masseter by palpation while asking the patient to bite hard.
Weakness in the facial muscles may result from:
- Upper motor neuron lesion:Here only the muscles of the lower part of face are affected. The eye closure is normalThis is because the muscles of the lower part (unlike those of the lower part) are activated through the upper motor neuron fibers of both sidesSpontaneous emotional expression is unaffected
- Lower motor neuron lesion:All the muscles of the face (upper and lower) are affected on the same sideFacial nerve passes through parotid gland but does not supply itFacial nerve supplies submandibular and lacrimal glands
Arterial supply to facial nerve: ascending pharyngeal artery.
Facial Nerve has:
- The longest intraosseous course
- It is the Mc paralyzed cranial nerve
Muscles supplied by facial nerve:
- Platysma
- Stylohyoid
- Muscles of facial expression
- Buccinator
- Stapedius
- Posterior belly of digastric
- Submandibular, Lacrimal, nasal gland
- Supplies gustatory sensation to soft palate
- Kindly never forget that despite the fact that facial nerve traverses the substance of parotid but does not supply it. (keeps it high and dry)
Facial nerve is related to
- Pterygopalatine ganglion
- Geniculate ganglion submandibular ganglion
Submandibular
The Eight (Vestibulocochlear) Nerve Palsy
The eighth nerve consists of two parts which have different functions Cochlear and vestibular nerves
- The cochlear part is concerned with hearing. An affection results is tinnitus and deafness
- The vestibular part is concerned with equilibrium. Its affection may result in vertigo.
The Ninth (Glossopharyngeal) Nerve Palsy
Paralysis of Glossopharyngeal nerve causes:
- Anesthesia of the pharynx
- Loss of taste on the posterior third of the tongue
Glossopharyngeal nerve is involved in:
- Jugular foramen syndrome: Involving IX, X, XI cranial nerves
- Collet Sicard Syndrome: Involving IX, X, XI, XII cranial nerves (Extracranially)
- Villaret Synrome: Lesion in retropharyngeal space involving IX, X, XI, XII cranial nerves
Paralysis of vagus nerve causes:
Ipsilateral paralysis of the palate,
Ipsilateral paralysis of the pharynx and
Ipsilateral paralysis of the larynx with anesthesia of the larynx on the affected side
Remember: The Recurrent Laryngeal nerve arises from vagus. On the Right side it winds around the subclavian artery and on the Left side it winds around the aortic arch behind ligamentum arteriosum.
The Eleventh (Accessory) Nerve Palsy
As a Result of damage to the Accessory nerve
Sternomastoids
Unilateral
Apparent wasting
The muscle does not stand out on testing
Bilateral
Wasting of the neck which appears like that of a chicken
Falling of head backwards
Trapezius
Unilateral paralysis
- Drooping of the shoulder when arm is hanging
- Weak movements on testing
Supplies all palatal muscles except Tensor palate
Spasmodic torticollis is due to central irritation of this nerve (cranial part)
The Twelfth (Hypoglossal) Nerve Palsy
- Lesion of one hypoglossal nerve results in deviation of the tongue ‘towards the paralyzed side’. If you ask the patient to protrude his tongue the muscles of the same side of the lesion become paralyzed and begin to atrophy (lower motor neuron lesion)
- Safety muscle of tongue is geniglossus supplied by hypoglossal nerve.
GEMS NEVER TO BE FORGOTTEN
The Pituitary Gland
Also known as Hypophysis cerebri. Pineal is Epiphysis cerebri
The average adult pituitary measures 11 × 15 × 5 mm
The gland is oval, bilaterally symmetrical, and brownish red
The pituitary is approximately 20% larger in females than in males and it enlarges about in females during pregnancy
It lies within the sella turcica (Turkish saddle)
This fossa is bordered anteriorly, posteriorly, and inferiorly by the sphenoid bone and laterally by the cavernous sinus
The floor of the sella forms the roof of the sphenoidal sinus
The diaphragma sellae, a thick reflection of dura mater, covers the roof of the sella and closely encircles the pituitary stalk in 50% of individuals
The arterial supply to the hypothalamic-pituitary region is complex and arises from three sources
- The inferior hypophyseal artery, a branch of the carotid artery, supplies the posterior pituitary.
- The superior hypophyseal arteries branch from the circle of Willis to supply the median eminence
- The middle hypophyseal arteries are of variable origin and supply the pituitary stalk
Capillary portions of the superior hypophyseal arteries drain from the hypothalamus, the median eminence, and the superior portions of the pituitary stalk. These vessels drain into the hypophyseal portal system, which forms a secondary venous plexus in the anterior pituitary and ultimately empties into the cavernous sinus. This portal venous system constitutes the principal blood supply to the anterior pituitary and serves as the medium through which releasing hormones from the hypothalamus reach the pituitary.
The Anterior pituitary arises from embryonic ectoderm (Rathke’s pouch) and includes the pars distalis, pars intermedia (vestigial in humans), and pars tuberalis
The Posterior pituitary of the gland arises from the diencephalon and includes the neural stalk, infundibulum, and posterior lobe
Embryonic defects in invagination and obliteration of the pharyngeal extent of Rathke’s pouch may lead to craniopharyngiomas or hormonally active ectopic pituitary adenomas.
Cavernous Sinus
- Paralysis of 3, 4, 6 cranial nerves indicates lesion of cavernous sinus
- Occulomotor, trochlear and ophthalmic nerves lie in lateral wall of cavernous sinus
- Abducent nerve is a direct content of cavernous sinus
- Infections from dangerous area of face can spread to cavernous sinus
Remember
The pituitary gland is located in the pituitary fossa within the skull. The floor of this fossa is formed by the sella turcica. The lateral walls of the fossa are formed by the cavernous sinuses. The abducens nerve passes through the cavernous sinus along with the internal carotid artery. As the tumor expands laterally, the first nerve that will be encountered is the abducens nerve, producing lateral rectus palsy.
Sympathetic and Parasympathetic Systems
Organ | Sympathetic | Parasympathetic |
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Pupil | Dilates | Constricts |
Lacrimal and salivary glands | Stops secretion | Produces secretion |
Heart | Accelerates | Slows |
Bronchioles | Dilates | Constricts |
Alimentary canal | Dilates | Contracts |
Urinary bladder | Dilates | Contracts |
Penis | Causes erection [For this reason the pelvic nerve was called the nervus erigens]. |
Limbic System
- Subcallosal Gyri
- Cingulate Gyri
- Hippocampal formation comprising of Hippocampal Gyrus, Parahippocampal Gyrus and Dentate gyrus
- Amygdaloidal nucleus
- Mammillary bodies
- Anterior thalamic nucleus
Briefly Functions of the Limbic System can be summarized by Five Fs
- Feeding
- Flight
- Feeling
- Fighting and
- Fun {sex}
What Passes through What
Foramen | Contents |
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Cerebrospinal Fluid (CSF)
- Clear fluid
- Colorless fluid
- Choroid Plexus (formed by)
- Chloride content ↑
- Cells minimal
- Cushions the brain
- Circulus arteriosus (branches) supply choroids plexus
- CSF is principally secreted by choroid plexus
- Choroid plexus is absent in anterior horn of lateral ventricle
- Total volume of CSF 150 ml
- Normal adult CSF pressure: 6 —12 mm Hg
- pH of CSF is: 7.33
- Epidural space is devoid of CSF
- Rate of CSF absorption is the main factor controlling CSF Pressure
- Persistent leakage can cause headache
- No neutrophils in normal state seen
ARTERIAL TERITORIES IN HEAD AND NECK AND CLINICAL CORRELATION
(USMLE Favorite)
* Occlusion of the vertebral artery may cause Medial Medullary Syndrome which is characterized by:
- Paralysis or atrophy of tongue on the side of lesion (XII nerve involvement)
- Paralysis of arm and leg on opposite side
- Impaired tactile and proprioceptive sense on opposite side. (Involvement of pyramidal tract and medial lemniscus)
- It is the largest and main branch of the vertebral artery
- It has a tortuous S-shaped course. Immediately after it arises from the vertebral artery, it runs backwards around the lower end of the olive passing through the rootless of the hypoglossal nerve, it then turns round the inferior cerebellar peduncle and finally divides into two terminal branches which supply: (a) the inferior vermis (b) the posterior part of the inferior surface of the cerebellum.
- Impaired pain and temperature sense on opposite side
- Nystagmus (involvement of vestibular nucleus)
- Dysphagia (involvement of nucleus ambigus)
- Nystagmus (involvement of cerebellum)
- Horner’s syndrome (involvement of sympathetic pathway)
Occlusion of the Anterior Spinal Artery May Cause
- Loss of motor function below the level of the lesion (due to damage to the corticospinal tracts)
- Loss of pain and temperature Sensation below the level of the lesion (due to damage to the spinothalamic tracts)
- Weakness of limbs (due to damage of the anterior grey horns in the cervical or lumbar regions of the cord)
- Loss of bowel and bladder control (due to damage of the descending autonomic tracts)
Occlusion of the Posterior Spinal Artery May Cause
Loss of position sense, vibration sense and light touch due to damage of the posterior white columns
Larynx
Larynx has three paired and three unpaired cartilages
Extends from C3-C6
Anatomic basis of stridor is in larynx
The larynx serves as the sounding source for speech. A fundamental tone is produced by the movement of the vocal cords, which is brought about by the flow of exhaled air past lightly approximated vocal cords
- The internal laryngeal nerve is sensory to larynx above vocal cords
- The recurrent laryngeal nerve is sensory to larynx below vocal cords
- All muscles of larynx except cricothyroid are supplied by recurrent laryngeal nerve
- Cricothyroid supplied by External laryngeal nerve
Muscles of Larynx and their Action
Abductor of vocal cords: Posterior Cricoarytenoid
Adductor of vocal cords:
- Lateral cricoarytenoid
- Transverse arytenoids
- Cricothyroid
- Thyroarytenoid
Tensor of vocal cords: Cricothyroid
Relaxor of vocal cords:
- Thyroarytenoids
- Vocalis
- Depression: Lateral Pterygoid
- Elevation: Temporalis, Massetter, Medial Pterygoid
- Protrusion: Pterygoids
- Retraction: Posterior fibers of Temporalis
- Lateral movements: Pterygoids
- Buccinator: Nota muscle of mastication
In Simple Terms
- The backward movement step is accomplished by the posterior fibers of the temporalis muscle
- The digastric helps to depress the lower jaw during chewing
- The lateral pterygoid helps to move the lower jaw forward during chewing
- The medial pterygoid helps to elevate the lower jaw during chewing
- The mylohyoid helps to depress the lower jaw during chewing
Ansa Cervicalis
Ansa cervicalis is a thin nerve loop that lies in the anterior wall of carotid sheath
Superior root is a continuation of descending branch of hypoglossal (XII) Cranial nerve. Superior root supplies Superior belly of omohyoid. Its fibers are derived from first cervical nerve
Inferior root is derived from spinal nerves C2 and C3
Loop of Ansa supplies:
- Inferior belly of omohyoid
- Sternothyroid
- Sternohyoid
Dangerous Areas: (USMLE Favorite)
- Dangerous area of face: Lowerpart of nose and upper lip
- Dangerous area of scalp: Loose areolar tissue layer of scalp
- Dangerous zone of eye: Ciliary body
Commonest Sites
- Commonest site of BHP: Periurethral zone
- Commonest site of cancer prostate: peripheral zone
- Commonest site of varicocele: Left side
- Commonest position of appendix: Retrocecal
- Commonest site of internal hemorrhoids: 3, 7 and 11 O’clock
Superficial Cutaneous Reflexes
Reflex | Stimulus | Response | Center – spinal segment involved |
---|---|---|---|
Scapular | Irritation of skin at the interscapular space | Contraction of scapular muscles and drawing in of scapula | C5 to T1 |
Upper abdominal | Stroking the abdominal wall below the costal margin | Ipsilateral contraction of abdominal muscle and movement of umbilicus towards the site of stroke | T6 to T9 |
Lower abdominal | Stroking the abdominal wall at umbilical and iliac level | Ipsilateral contraction of abdominal muscle and movement of umbilicus towards the site of stroke | T10 to T12 |
Cremasteric | Stroking the skin at upper and inner aspect of thigh | Elevation of testicles | L1, L2 |
Gluteal | Stroking the skin over glutei | Contraction of glutei | L4 to S1, S2 |
Plantar | Stroking the sole | Plantar flexion and adduction of toes | L5 to S2 |
Bulbocavernous | Stroking the dorsum of glans penis | Contraction of bulbocavernous | S3, S4 |
Anal | Stroking the perianal region | Contraction of anal sphincter | S4, S5 |
- Emotion
- Memory
- Higher functions
- Consolidation of long-term memory occurs in hippocampus
- Processing of short term memory to long term occurs in hippocampus
- Amygdala is the window of limbic system
- Damage to amygdala causes Kluver Bluck syndrome
- Reward center is in medial forebrain bundle.
Herniations
- Uncal or transtentorial herniation. The herniated uncus will compress the oculomotor nerve, the posterior cerebral artery, and the brainstem. The pathophysiologic consequences include oculomotor paralysis (manifesting with fixed and dilated pupil on the same side), ipsilateral infarction of the occipital lobe, and hemorrhages within the midbrain and pons. The latter may result in respiratory paralysis and death
- Cerebellar tonsillar herniation refers to downward displacement of the cerebellar tonsils through the foramen of magnum. This results from space-occupying lesions in the infratentorial compartment, such as bleeding and tumors. It leads to compression of the medulla and death by cardiorespiratory arrest
- Subfalcine (cingulate) herniation describes the lateral displacement of the cingulate gyrus beneath the falx cerebri. This event is caused by space-occupying masses in the cerebral hemisphere. It leads to compression of the anterior cerebral artery and infarction of dependent cerebral territories (mostly the medial portion of the frontal and parietal lobes)
- Reverse cerebellar herniation is a rare form of herniation due to midbrain lesions (again, hemorrhages and tumors) that push the midbrain upward through the incisura of the tentorium
- Transcalvarial herniation may develop in open (i.e. accompanied by calvarial bone fractures) head injuries if brain parenchyma is displaced outside the cranial cavity through a calvarial defect
- Split brain syndrome: Disconnection syndrome of cerebral cortex resulting from transection or congenital absence of cerebral cortex.
Types of Fibers in CNS
Association fibers: Connecting different areas of same cerebral hemisphere
- Superior longitudinal fasiculus
- Inferior longitudinal fasiculus
- Cingulum
- Uncinate fasiculus
- Corticospinal tract
- Internal capsule
Commisural fibers: connecting corresponding parts of two cerebral hemispheres
- Corpus callosum
- Anterior commisure
- Posterior commisure
- Hippocampal commisure
- Habenular commisure
- Hypothalmic commisure
Effects | Upper motor neuron | Lower motor neuron lesion | |
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Clinical observation | Muscle tone | Hypertonic | Hypotonic |
Paralysis | Spastic type of paralysis | Flaccid type of paralysis | |
Wastage of muscle | No wastage | Present | |
Superficial reflexes | Lost | Lost | |
Plantar reflex | Abnormal – babinski’s sign | Absent | |
Deep reflexes | Exaggerated | Lost | |
Clonus | Present | Lost |
Anatomy of Eye: (USMLE Favorite)
- The ‘Extroter’ of Eye ball is Inferior Oblique and Inferior Rectus
- The ‘Introter’ of Eye ball is Superior Oblique and Superior Rectus.
- Action of Superior oblique is Abduction, Intorsion and depression
- Dilator Pupillae dilates pupil and is supplied by Sympathetics
- Sphincter Pupillae constricts pupil and is supplied by Parasympathetics
- LR6S04
- Lateral rectus is supplied by 6th Cranial Nerve (Abducent)
- Superior oblique is supplied by 4th Cranial Nerve (Trochlear)
- Rest other ocular muscles are supplied by 3rd Cranial Nerve (Occulomotor)
- Muscle attached to posterior tarsal margin: Mullers muscle
- Ligament of Lockwood is found in Orbit.
Structures passing through ‘Superior Orbital Fissure’ are
Live Free To See No Insult at All
- Lacrimal Nerve
- Frontal Nerve
- Trochlear Nerve
- Superior Ophthalmic Vein
- Nasociliary Nerve
- Inferior Ophthlamic Vein
- Abducent Nerve
- Maxillary nerve
- Zygomatic nerve
- Infraorbital vessels
- Orbital branch of pterygoplatine ganglion
Lesions and Effects of (Visual Pathway)
- Central scotoma ~ macula
- Ipsilateral blindness ~ optic nerve
- Bitemporal hemianopia ~ optic chiasm
- Homonymous hemianopia ~ optic tract
- Upper homonymous quadrantanopia ~ temporal optic radiations
- Lower homonymous quadrantanopia ~ parietal optic radiations
- Also, cortical lesions produce defects similar to those of the optic radiations, but may spare the macula.
Spinal Cord
- Spinal cord in adults ends at L1- L2
- Spinal cord in infant sends at L3
- Thoracic and sacral curves are concave anteriorly
- Subarachnoid space/Subdural space ends at S2
- Dural sheath ends at S2
- Filum terminale and piamater extend up to tip of coccyx
- Number of spinal nerve pairs: 31.
Cauda Equina Syndrome
It is a serious neurologic condition in which there is acute loss of function of the lumbar plexus, neurologic elements (nerve roots) of the spinal canal below the conus of the spinal cord
After the conus, the canal contains a mass of nerves (the cauda equina or ‘horse-tail’) that branches off the lower end of the spinal cord and contains the nerve roots from L1-5 and S1-5. The nerve roots from L4-S4 join in the sacral plexus which affects the sciatic nerve, which travels caudally (toward the feet)
| C1-C7 Add1 |
| T1 –T6 Add 2 |
| T7-T9 Add 3 |
| Corresponds to L1-L2 |
| Corresponds to L5-S1 |
Ascending Tracts of Spinal Cord
Situation | Tract | Function |
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Anterior white funiculus | Anterior spinothalamic tract | ‘Crude‘ touch sensation |
Lateral spinothalamic tract | Pain and temperature sensation | |
Ventral spinocerebellar tract | Subconscious kinesthetic sensations | |
Dorsal spinocerebellar tract | Subconscious kinesthetic sensations | |
Lateral white funiculus | Spinotectal tract | Concerned with spinovisual reflex |
Fasiculus dorsolateralis | Pain and temperature sensations | |
Spinoreticular tract | Conciousness and awareness | |
Spino olivary tract | Proprioception | |
Spinovestibular tract | Proprioception | |
Fasciculus gracilis | Tactile sensation | |
Posterior white funiculus | Fasciculus cuneatus | Tactile localization |
Tactile discrimination | ||
‘Vibratory’ sensation | ||
‘Conscious kinesthetic sensation’ | ||
‘Stereognosis’ |
Descending Tracts of Spinal Cord
Situation | Tract | Function |
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Pyramidal tracts | Anterior corticospinal tract |
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Lateral corticospinal tract |
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Extra Pyramidal tracts | Medial longitudinal fasciculus |
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Anterior vestibulospinal tract |
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Lateral vestibulospinal tract | ||
Reticulospinal tract |
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Tectospinal tract |
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Rubrospinal tract |
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Olivospinal tract |
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- Hand E Stain (Hematoxylin and Eosin): Hematoxylin, a natural dye product, acts as a basic dye that stains blue or black. Nuclear heterochromatin stains blue and the cytoplasm of cells rich in ribonucleoprotein also stains blue
- The aniline dye, Eosin, is an acid dye that stains cytoplasm, muscle, and connective tissues various shades of pink and orange. This difference in staining intensity is useful in differentiating one tissue from another
- Vital Stain: Such as Neutral red, Trypan blue are used for staining living cells such as Reticuloendothelial cells
- Metachromatic Stains are used for staining mast cells with Toluidine blue. The stains react with granules of mast cells (metachromasia) to give a new color to the cells
- Periodic Acid-Schiff Method (PAS): Principally used to demonstrate structures rich in carbohydrate macromolecules such as glycogen, glycoprotein, and proteoglycans found in ground substance of connective tissues, basement membranes and mucus
- Phosphotungstic Acid Hematoxylin (PTAH): This is an ideal stain for the demonstration of striated muscle fibers and mitochondria, which stain blue
- Silver Stains: Certain tissue components called Argyrophilic have a natural affinity for silver salts. Reticular fibers and the granules in diffuse endocrine cells are argyrophilic
- Sudan Stains: Sudan dyes are used to stain lipids. The Sudan dyes, e.g. Sudan IV, dissolve in droplets containing triglycerides and color them intensely.
Important Points about Vessels: (USMLE Favorite)
- Umbilical arteries carry venous blood
- Pulmonary vasculature also follows reverse pattern
- Coronary arteries have three elastic lamina: Internal, middle and external
- Umbilical arteries have no elastic lamina
- The arteries of lower limb have more developed muscular tissue than those of upperlimb
IMPORTANT POINTS ABOUT SKULL BONES Skull
Scaphocephaly | Boat shaped skull due to premature union of saggital suture |
Acrocephaly/Oxycephaly | Pointed skull due to premature union of coronal suture |
Plagiocephaly | Twisted skull due to assymetrical union of sutures |
Trigonocephaly | Triangular prominence of forehead due to premature fusion of metopic suture |
Brachycephaly | Short and broad skull |
Seen in Cleidocranial dysostosis | |
Seen in Downs Syndrome | |
Seen in Achondroplasia | |
Dolicocephaly | Long and thin skull |
Seen in Marfans syndrome | |
Anencephaly | Vault of skull not developed resulting in the absence of a major portion of the brain, skull, and scalp |
Pneumatic Bones: (USMLE Favorite)
- Contain air spaces. Usually present in skull
- Make the skull light in weight
- Act as air conditioners
- Maxilla
- Sphenoid
- Ethmoid
- Mastoid Bones
- Patella
- Pisiform
- Fabella
Bones Ossified at Birth
- Lower end of femur
- Upper end of tibia
- Calcaneum
Important Points about Muscles
- Anti rape muscle/muscle virgineous: Gracilis
- Cheating muscle: Superior oblique of eye
- Safety muscle of tongue: Genioglossus
- Tailors muscle: Sartorius
- Thermostat of testis cremaster
- Bladder muscles in whorls detrusor
Hybrid/Composite Muscles
- Adductor magnus
- Biceps Femoris
- Pectineus
- Digastric
- Flexor digitorum superficialis
Digastric Muscles
- Digastric: Anterior belly, posterior belly
- Omohyoid: Superior belly, inferior belly
- Occipitofrontalis: Occipital belly, frontal belly
- Gastrocnemius: Lateral head, medial head
- Ligament of Treitz: Skeletal part, smooth part
Important Lymph Nodes (USMLE Favorite)
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- Cloquets node/Rossenmullers node
- Mucocutaneous lymph node syndrome
- Sister mary josephs node
- Virchows node
- Rotter’s lymph nodes are small interpectoral lymph nodes located between the pectoralis major and pectoralis minor muscles. They receive lymphatic fluid from the muscles and the mammary gland, and deliver lymphatic fluid to the axillary lymphatic plexus.
Thoracic duct
- Thoracic duct starts as continuation of cisterna chylii
- Crosses from right to left at four level
- Passes through aortic opening of diaphragm
- The right lymphatic duct drains the right arm, the right side of the chest, and the right side of the head. The thoracic duct drains the rest of the body. Both the right lymphatic duct and the thoracic duct dump into the large venous channels at the base of the neck. Occlusion of this drainage cans produce intractable edema in sites feeding these ducts.
Primary lymphoid organs are Thymus and Bone marrow
Lymphatics are absent in
- Epidermis
- Eye
- Cornea
- Lens
- Articular cartilage
- Placenta
- Bone marrow
- Glottis
Eponym Nerves: (USMLE Favorite)
- Arnolds nerve/Aldermans nerve auricular branch of vagus
- Nerve of Bell long thoracic nerve
- Buffer nerve carotid sinus and vagal fibers from aortic arch
- Saphenous nerve longest/largest cutaneous branch of femoral nerve
- Herrings nerve branch of glossopharyngeal nerve to carotid sinus
- Exners nerve from pharyngeal plexus to cricothyroid membrane
- Vidian nerve Greater pertrosal + deep pertrosal nerve (N of Pterygoid canal)
- Nerve of Wrisberg: (2 nerves) Nervus intermedius (branch of Facial nerve), medial cutaneous nerve of forearm
Freys syndrome/Baillargers Syndrome
Due to abnormal and inappropriate regeneration Auriculotemporal branch of trigeminal nerve there is rednesss, sweating especially on cheeks while eating, talking (gustatory sweating)
Important Points about Veins
- Great cerebral vein of Galen is formed by union of internal cerebral veins
- Great cerebral vein of Galendrains into straight sinus
- Facial vein communicates to cavernous sinus via: Superior ophthalmic vein, inferior ophthalmic vein, deep facial vein
- Long saphenous vein is the largest and longest superficial vein of lower limb formed on medial side of dorsal venous arch
- Injury to great saphenous vein corresponds to area of femoral nerve distribution.
- 79The portal vein begins at the level of the second lumbar vertebra and is formed from the convergence of the superior mesenteric and splenic veins. It is 3. 8 cm long and lies anterior to the inferior vena cava and posterior to the neck of the pancreas. It lies obliquely to the right and ascends behind the first part of the duodenum, the common bile duct and gastroduodenal artery. At this point it is directly anterior to the inferior vena cava. It enters the right border of the lesser omentum, and ascends anterior to the epiploic foramen to reach the right end of the porta hepatis. It then divides into right and left main branches which accompany the corresponding branches of the hepatic artery into the liver
- Portal vein is formed behind the neck of pancreas by union of superior mesentric and spleenic vein
- Normal pressure is 5–10 mm Hg
- Portal venous system is valveless.
- Left suprarenal drains into left renal vein
- Left testicular vein drains into left renal vein
- Left ovarian vein drains into left renal vein
- Batesons vertebral venous plexus is valveless
Varicose Veins
Are dilated, tortuous veins and are very common; they may either give no symptoms or cause aching and discomfort in the legs. Varices are recognized as tortuous dilated veins in the leg, a varicose vein is one which permits reverse flow through its faulty valves. Occasionally complications of varicose veins may develop. These include:
- Thrombosis: Which is referred to as superficial thrombophlebitis
- Sometimes thrombosis extends into the deep venous system to cause Deep vein thrombosis, although this is infrequent
- Hemorrhage: Can occur when large superficial varices are damaged
- The most serious problem is venous ulceration which complicates varicose veins.
Excepts in Anatomy
- All muscles are mesodermal in origin except muscles of Iris (Sphincter pupillae and dilator pupillae) which are ectodermal
- All Pharyngeal arches persist except fifth which disappears
- All intrinsic muscles of Larynx are supplied by recurrent laryngeal nerve except cricothyroid which is supplied by external laryngeal nerve
- All major salivary gland are supplied by facial nerve except Parotid gland (Although passes through the substance of parotid)
- All divisions of Trigeminal nerve except Mandibular division lie in lateral wall of Cavernous sinus
- All muscles of pharynx are supplied by pharyngeal plexus except stylopharyngeus which is supplied by Glossopharyngeal nerve.
- All muscles of soft palate are supplied by pharyngeal plexus except tensor palate which is supplied by Nerve to medial pterygoid
- All muscles of tongue are supplied by hypoglossal nerve except palatoglossus which is supplied by pharyngeal plexus.
Important Vessels and Source of Bleeding: (USMLE Favorite)
- Hemoptysis: Bronchial artery
- Duodenal ulcer: Gastroduodenal artery
- Gastric ulcer: Left Gastric artery
- SDH: Bridging veins
- EDH: Middle meningeal artery
- Tonsillectomy: Paratonsillar vein
- Menstruation: Spiral arteries
Duodenal ulcer: The duodenal cap lies just beyond the pylorus. Externally, the cap has attachments to the hepatoduodenal ligament in the pancreatic head. Most of the ulcers occur in the duodenal cap region. The gastroduodenal artery lies directly behind the duodenal cap, and penetrating ulcers into the pancreas initially erode through the gastroduodenal artery, accounting for the massive bleeding that occurs with these ulcers
Extradural hemorrhage: Usually follows arterial hemorrhage between the skull and the dura. Most frequently, acute epidural hematomas occur in the temporal or temporoparietal region as a consequence of hemorrhage from one of the branches of the middle meningeal artery.
- Parotid duct: Stensons duct
- Submandibular duct: Whartons duct
- Pancreatic duct: Wirsungs duct
- Accessory pancreatic duct: Santoniris duct
- Gartners duct: Remanant of Mesonephric duct (WOLLFIAN)
- Thoracic duct: Pecquet duct
Important Membranes in Body: (USMLE Favorite)
| Inner layer of cells of root sheath of hair |
| Outer layer of cells of root sheath of hair |
| 'Anterior’ limiting membrane of Cornea |
| ‘Posterior’ limiting membrane of Cornea |
| Pigment membrane in Retina |
| Astroglial membrane covering Optic Disk |
| Exocelomic Membrane |
| Pars Flaccida of the tympanic membrane |
Important Cells in Histology (USMLE Favorite)
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Reed Sternberg cell
These cells characteristically are neoplastic giant cells with a bilobed mirror-image nucleus that may have large (‘owl-eyes’) nucleoli surrounded by a clear halo. Most commonly, these cells are associated with Hodgkin’s disease.
The Langhans cell
It is a giant cell with peripherally arranged nuclei found in granulomas
The LE cell
It is a degenerating neutrophil seen in lupus erythematosus in in vitro preparations
The Mott cell
It is a ‘constipated’ plasma cell filled with immunoglobulins, producing a grape-cluster appearance to the cell. Mott cells are seen in multiple myeloma and some parasitic infestations
The Touton giant cell
Has distributed nuclei and is found in tumors other than Hodgkin’s lymphoma
Diaphragms of Body (USMLE Favorite)
- Diaphragm of oral cavity: Mylohyoid
- Diaphragm of Superior thoracic aperture: Sibsons Fascia
- Pelvic diaphragm: Levator ani and coccygeus
- Urogenital diaphragm: Deep transverse perinea and sphincter urethrae, perineal mermbrane
- Diaphragm sella: Fold of duramater overlying pituitary fossa
- Iris diaphragm: In eye
Eponym Fascias (USMLE Favorite)
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USMLE Case Scenario
The Fascial layer separating the rectum from the coccyx is:
- Waldeyers Fascia
- Fascia Coli
- Denonveliers Fascia
- Gerota’s Fascia
- Cruveilhier’s Fascia
- Camper’s Fascia
- Colles’ Fascia
- Scarpa’s Fascia
Ans. 1. Waldeyers Fascia
Bursitis
Bursitis is inflammation of a bursa, which is a thin-walled sac lined with synovial tissue
The function of the bursa is to facilitate movement of tendons and muscles over bony prominences:
- Subacromial bursitis (subdeltoid bursitis) is the most common form of bursitis. Trochanteric bursitis involves the bursa around the insertion of the gluteus medius onto the greater trochanter of the femur.
- Olecranon bursitis occurs over the posterior elbow, and when the area is acutely inflamed, infection should be excluded by aspirating and culturing fluid from the bursa. Achilles bursitis involves the bursa located above the insertion of the tendon to the calcaneus and results from overuse and wearing tight shoes.
- Retrocalcaneal bursitis involves the bursa that is located between the calcaneus and posterior surface of the Achilles tendon.
- Ischial bursitis (weaver’s bottom) affects the bursa separating the gluteus medius from the ischial tuberosity and develops from prolonged sitting and pivoting on hard surfaces.
- Iliopsoas bursitis affects the bursa that lies between the iliopsoas muscle and hip joint and is lateral to the femoral vessels.
- Anserine bursitis is an inflammation of the sartorius bursa located over the medial side of the tibia just below the knee and under the conjoint tendon and is manifested by pain on climbing stairs.
- Prepatellarbursitis (housemaid’s knee) occurs in the bursa situated between the patella and overlying skin and is caused by kneeling on hard surfaces. Treatment of bursitis consists of prevention of the aggravating situation, rest of the involved part, administration of a nonsteroidal anti-inflammatory drug (NSAID), or local glucocorticoid injection.
Bursitis of Knee Joint
- Housemaid’s knee is the result of inflammation of Prepatellar bursa
- Miners beat knee is the result of inflammation of Prepatellar bursa
- Clergymans knee is the result of inflammation of subcutaneous infrapatellar bursa
Important Nutrient Arteries
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Axis artery of upper limb: seventh cervical intersemental artery persisting as:
- Axillary
- Brachial
- Anterior interosseous artery and
- Deep palmar arch
Axis artery of lower limb: fifth lumbar intersemental artery persisting as:
- Inferior gluteal artery
- Companion artery of sciatic nerve
- Popliteal artery
- Peroneal artery and
- Plantar arch
Important Vessels (USMLE Favorite)
The Marginal artery of Drummond is also known as the Marginal artery of the colon.
The anastomoses of the terminal branches of the ileocolic, right colic and middle colic arteries of the continuous arterial circle or arcade along the inner border of the colon known as the marginal artery of Drummond.
Components
- Ileocolic artery - colic branch
- Right colic artery – ascending and descending branches
- Middle colic artery – right and left branches
- Left colic artery – ascending and descending branches
- Sigmoid arteries – unnamed terminal branches
- From this marginal artery, straight vessels (known as vasa recta) pass to the colon
- The marginal artery is an important connection between the SMA and IMA, and provides collateral flow in the event of occlusion or significant stenosis. The junction of the SMA and IMA territories is at the:
- Superior mesentric artery (SMA), and of the left colic and sigmoid branches of the IMA, form a splenic flexure. Anastomoses here are often weak or absent, hence the marginal artery at this point (known as Griffiths’ point) is often focally small or discontinuous. For this reason, the splenic flexure is a watershed area prone to ischemia and infarction
- One of the commonest area of colonic ischemia is called Sudeck’s point.
Charcots Artery
Charcots Artery: lenticulostriate arteries which arise at the commencement of the middle cerebral artery supply blood to part of the basal ganglia and posterior limb of the internal capsule. The lenticulostriate perforators are end arteries. The name of these arteries is derived from some of the structures it supplies: the lenticular nucleus and the striatum.
Heubner’s Artery
Heubner’s artery: A branch of anterior Cerebral artery, supplies the anteromedial part of the head of the caudate and anteroinferior internal capsule Its vascular territory is the anteromedial section of the caudate nucleus and the anteroinferior section of the internal capsule.
Artery of Adamkiewicz: Arteria Radicularis Magna, Great radicular artery of Adamkiewicz. Provides the major blood supply to the lumbar and sacral cord. When damaged or obstructed, it can result in anterior spinal artery syndrome, with loss of urinary and fecal continence and impaired motor function of the legs; sensory function is often preserved to a degree. It is important to identify the location of the artery when treating a thoracic aortic aneurysm or a thoracoabdominal aortic aneurysm.
The Dorsalis Pedis Artery
- The dorsalis pedis artery is the continuation of the anterior tibial artery after the artery anterior tibial artery crosses the ankle to reach the dorsum of the foot
- Its pulse is the most distal palpable pulse in the lower limb and therefore is useful for evaluating the arterial supply to the limb
- On the dorsum of the foot, the pulse maybe felt as the artery passes over the navicular bone between the extensor hallucis longus tendon and the extensor digitorum longus tendon.
Batson’s Vertebral Venous Plexus
Batson’s vertebral venous plexus: The valveless vertebral venous veins that communicate with the prostatic venous plexus and explain the readiness with which carcinoma of the prostate spreads to the pelvic bones and vertebrae.
Tortuous Arteries
- Facial artery
- Splenic artery
- Uterine artery
- Vaginal artery
- Ophthalmic artery
- Lingual artery
- PICA (Post Inferior Cerebellar Artery)
USMLE Case Scenario
A 66-year-old male patient from Florida complains of loss of pain and temperature sensation over the left side body ipsilateral dysphagia, hoarseness, and diminished gag reflex with vertigo and diplopia of two months duration. Most likely tortuous vessel affected is:
- AICA
- PICA
- Common carotid
- Internal carotid
- Arch of aorta
Ans. 2. PICA: The condition itself is Lateral Medullary (Wallenburgs Syndrome)
End Arteries
- Central artery of retina
- Central branches of cerebral artery
- Coronary artery
- Segmental branches of renal/splenic artery
Important Arteries and Their Branches: (USMLE Favorite)
Internal Carotid Artery
No Branches in Neck
- Caroticotympanic
- Pterygoid
- Cavernous branch to trigeminal ganglion
- Superior and inferior hypophyseal
- Ophthalmic
- Anterior cerebral
- Middle cerebral
- Posterior communicating
- Anterior choridal
External Carotid Artery
- Superior thyroid
- Lingual
- Facial
- Occipital
- Posterior auricular
- Ascending pharyngeal
- Maxillary
- Superficial temporal
Subclavian Artery
- Vertebral artery
- Internal thoracic artery
- Thyrocervical trunk (Inferior thyroid, suprascapular, superficial cervical)
- Costocervical trunk (Superior intercostal, Deep cervical)
Vertebral Artery
- Spinal
- Muscular
- Meningeal
- Anterior spinal
- Posterior spinal
- Posterior inferior cerebellar
- Medullary
- Formed by Union of Two Vertebral Arteries:
- Posterior cerebral arteries
- Superior cerebellar
- Pontine
- Labyrinthine
- Anteroinferior cerebellar
Internal Iliac Artery
- It is smaller terminal branch of common iliac artery
- It is about one and half inches long (3–3.5 cn)
- It begins in front of sacroiliac joint
- It divides into ant and post Divisions at upper margin of greater sciatic notch
Branches from Anterior Division: (Six in males and seven in females.)
- Superior vesical artery
- Inf vesical
- Obturator
- Middle rectal
- Inf Gluteal
- Internal pudendal
- In females, inferior vesical is replaced by vaginal artery
- Uterine artery is the 7th branch in females
Branches from Posterior Division
- Superior gluteal
- IIio lumbar
- Lateral sacral
Questions asked in USMLE Examinations
- Inferior thyroid artery is a branch of: Thyrocervical trunk
- Ascending pharyngeal artery is a branch of external carotid artery
- Internal pudendal artery in females is a branch of internal iliac artery
- Left gastroepiploic artery is a branch of splenic artery
- Splenic artery is a branch of celiac trunk
- Uterine artery is a branch of internal iliac artery
- Cystic artery is a branch of right hepatic artery
- Cilio retinal artery is a branch of choridal artery
- Middle meningeal artery is a branch of maxillary artery
- Anterior spinal artery is a branch of vertebral artery
- Ophthalmic artery is a branch of internal carotid artery
Structures Pasing between/Piercing
- Structure passing between two heads of gastrocnemius: Sural nerve
- Structure passing between two heads of lateral pterygoid: Maxillary artery
- Structure passing between pronator teres: Median nerve
- Structure passing through tarsal tunnel: Posterior tibial nerve
- Structure passing through choroid fissure of eye: Hyaloids artery
- Structure passing through foramen of Vesalius: Emissary vein
- Structure passing through carotid sheath: Internal carotid/common carotid artery, internal jugular vein, vagus nerve. External carotid is External to sheath
- Structure piercing corocabrachialis: Musculocutaneous nerve
- Structure piercing clavipectoral fascia (encloses subclavius): Lateral pectoral nerve, thoracoacromial vesses Cephalic vein
- Structure piercing thyrohyoid membrane: Internal laryngeal nerve
Important Structures ‘Accompanying’ (USMLE Favorite)
- Axillary nerve accompanies posterior humeral circumflex artery
- Radial nerve accompanies profunda brachii vessels
- Short saphenous vein accompanies sural nerve
- Great saphenous vein accompanies saphenous nerve
- Superior thyroid vessels accompany external laryngeal nerve
- Superior laryngeal vessels accompany internal laryngeal nerve
- Inferior laryngeal vessels accompany recurrent laryngeal nerve
USMLE Case Scenario
Stroking the skin of the medial side of the thigh evokes a reflex contraction of the muscle, the cremasteric reflex, which is most, pronounced in children. It may represent a protective reflex, and the cremaster may also have a role in testicular thermoregulation. Cremaster consists of loosely arranged muscle fasciculi lying along the spermatic cord. It is variable in thickness and is thickest in young men. It may form an incomplete coating around the cord, known as the cremasteric fascia, which extends around the testis but lies within the external spermatic fascia. Cremaster is innervated by:
- The terminal branches of the subcostal nerve
- The terminal branches of the iliohypogastric nerve
- The terminal branches of the ilioinguinal nerve
- The genital branch of the genitofemoral nerve
- The femoral branch of the genitofemoral nerve
Ans.4. The genital branch of the genitofemoral nerve
USMLE Case Scenario
A 45-year-old man is evaluated by a neurologist because of a gait disorder. When the physician passively moves the patient’s right great toe upward or downward, the patient cannot accurately report the direction of motion. This finding can best be explained by a lesion of which of the following structures?
- Right fasciculus cuneatus
- Right fasciculus gracilis
- Right lateral lemniscus
- Right medial lemniscus
Ans: 2. Right fasciculus gracilis
USMLE Case Scenario
As part of a complete neurological examination, a medical student takes a cotton-tipped applicator and touches the patient’s left eye with a thin wisp of cotton as the patient looks to the right. The patient closes both of his eyelids in response. Which of the following cranial nerves is responsible for the motor limb of this reflex?
- Abducens
- Facial
- Optic
- Trigeminal
Ans.2. Facial
USMLE Case Scenario
The Epithelium of the Bronchi contains:
- Simple ciliated columnar cells, basal cells, and goblet cells
- Simple ciliated columnar cells, basal cells, but not goblet cells
- Non ciliated columnar cells, basal cells, and goblet cells
- Stratified ciliated columnar cells, basal cells, and goblet cells
Ans.4. Stratified ciliated columnar cells, basal cells, and goblet cells
USMLE Case Scenario
The Dandy-Walker malformation is a developmental abnormality in which:
- In which the roof of the third ventricle fails to perforate with concomitant hyperplasia of the cerebellar vermis
- In which the roof of the fourth ventricle fails to perforate with concomitant hyperplasia of the cerebellar vermis
- In which the roof of the third ventricle fails to perforate with concomitant hypoplasia of the cerebellar vermis
- In which the roof of the fourth ventricle fails to perforate with concomitant hypoplasia of the cerebellar vermis
Ans.4. In which the roof of the fourth ventricle fails to perforate with concomitant hypoplasia of the cerebellar vermis.
89The Dandy-Walker malformation is a developmental abnormality in which the roof of the fourth ventricle fails to perforate to form the foramen of Magendie. The resultant cystic dilatation of the fourth ventricle expands the posterior fossa, elevating the tentorium and causing hydrocephalus because of obstruction of the aqueduct of Sylvius, with concomitant hypoplasia of the cerebellar vermis.
USMLE Case Scenario
The kidneys and ureter arise from:
- The pronephros and a diverticulum from the wolffian duct
- The mesonephros and a diverticulum from the wolffian duct
- The metanephros and a diverticulum from the wolffian duct
- The pronephros and a diverticulum from the gartners duct
- The mesonephros and a diverticulum from the gartners duct
- The metanephros and a diverticulum from the gartners duct
Ans.2. The mesonephros and a diverticulum from the wolffian duct.
USMLE Case Scenario
From its origin, the uterine artery crosses the ureter anteriorly in the broad ligament before branching at the level of the uterus. One major branch ascends the uterus tortuously within the broad ligament until it reaches the region of the ovarian hilum where it anastomoses with branches of the ovarian artery. The uterine artery arises as a branch of:
- The anterior division of the internal iliac artery
- The anterior division of the external iliac artery
- The posterior division of the internal iliac artery
- The posterior division of the external iliac artery
- The common iliac artery
Ans.1. The anterior division of the internal iliac artery
USMLE Case Scenario
A 34-year-old patient arrives in the emergency room after having suffered severe head trauma in a accident. Radiographic studies of the head reveal a basilar skull fracture in the region of the foramen ovale. Which of the following nerve passes through this foramen:
- Maxillary
- Mandibular
- Ophthalmic
- Occulomotor
Ans.2. Mandibular
USMLE Case Scenario
A Lecturer in Florida is demonstrating a thick fibrous band that runs on the visceral surface of the liver. It is attached on one end to the inferior vena cava and on the other end to the left branch of the portal vein. In the Adult the structure corresponds to:
- Ductus venosus
- Ligamentum teres
- Ligamentum venosum
- Umbilical arteries
- Ligamentum arteriosum
- Ligamentum nucha
- Ligament of Treitz
Ans.3. Ligamentum venosum
USMLE Case Scenario
A Lecturer in Florida is demonstrating a fibrous band that runs on the visceral surface of the liver. It is attached on one end to the inferior vena cava and on the other end to the left branch of the portal vein. In the embryo structure corresponds to:
- Ductus venosus
- Ligamentum teres
- Ligamentum venosum
- Umbilical arteries
Ans.1. Ductus venosus
USMLE Case Scenario
A 66-year-old driver suffers a stroke while driving on highway. He has a history of hypertension, is a heavy smoker, and drinks beer every weekend A right upper motor neuron paralysis of the facial nerve is noted; the other cranial nerves are normal. He has a hemiplegia on the right side, with equal paralysis of the arm and leg. His lesion most likely involves the:
- Left internal capsule
- Left midbrain
- Left pons
- Left medulla
Ans.1. Left internal capsule
Remember:
The anterior limb of the internal capsule conveys frontopontine fibers, the genu conducts corticobulbar fibers, and the posterior limb of the internal capsule conveys corticospinal fibers to the contralateral arm and leg. Hemorrhage of the left internal capsule results in right-sided dense hemiplegia in which paralysis of the arm and leg are of the same intensity.
USMLE Case Scenario
A structure is caused by failure of obliteration of the vitellointestinal duct. It is classically located in the distal ileum within 30 cm of the ileocecal valve, and the structure is a true diverticulum. The anatomist is talking about:
- Ligament of Trietz
- Meckel’s diverticulum
- Appendicis epiploicae
- Sacculations
Ans.2. Meckel’s diverticulum
USMLE Case Scenario
A newborn boy does not pass meconium until 48 hours after his birth. Several weeks later his mother complains that he has not been passing stool regularly. Anorectal manometry reveals increased internal anal sphincter pressure on rectal distention with a balloon. The patient’s disorder maybe attributed to distention with a balloon. The patient’s disorder maybe attributed to:
- Defective recanalization of the colon
- Herniation of abdominal contents into the umbilical cord
- Persistence of the proximal end of the yolk stalk
Ans.2. Failure of neural crest cells to migrate
USMLE Case Scenario
The vagina is a muscular tube lined with:
- Non stratified squamous epithelium that is histologically similar to the mucosa of the cervix and vulva
- Stratified squamous epithelium that is histologically similar to the mucosa of the cervix and vulva
- Stratified cuboidal epithelium that is not histologically similar to the mucosa of the cervix and vulva
- Stratified cuboidal epithelium that is histologically similar to the mucosa of the cervix and vulva
Ans.2. Stratified squamous epithelium that is histologically similar to the mucosa of the cervix and vulva.
USMLE Case Scenario
A 5-year-old child aspirates a peanut. Following bronchopulmonary segments would this foreign object most likely enter.
- Superior segment of the right lower lobes
- Inferior segment of the right lower lobe
- Superior segment of the left lower lobe
- Superior segment of the left lower lobe
Ans.1. Superior segment of the right lower lobe
Because the right main bronchus is wider and more vertical than the left, foreign objects are more likely to be aspirated into the right main bronchus. The superior segmental bronchus of the lower lobar bronchus is the only segmental bronchus that exits from the posterior wall of the lobar bronchi. Therefore, if a patient is supine at the time of aspiration, the object is most likely to enter the superior segmental bronchus of the lower lobe.
USMLE Case Scenario
Fracture of neck of Fibula produces foot drop due to injury of:
- Common peroneal nerve
- Tibial nerve
- Obturator nerve
- Femoral nerve
Ans: 1. Common peroneal nerv
USMLE Case Scenario
Which of the following embryonic structures gives rise to the adrenal cortex?
- Ectoderm
- Endoderm
- Mesoderm
- Mesonephros
Ans.3. Mesoderm
USMLE Case Scenario
USMLE Case Scenario
The arterial blood supply to the palatine tonsil is derived from branches of the external carotid artery. The principal artery is the tonsillar artery, which is a branch of the:
- Facial artery
- Lingual artery
- Superficial temporal artery
- Maxillary artery
- Superior thyroid artery
Ans.1. Facial artery
USMLE Case Scenario
Occlusion of which artery would result in insufficient perfusion of the urinary bladder:
- Internal iliac
- External iliac
- Renal
- Suprarenal
Ans.1. Internal iliac
USMLE Case Scenario
Statement True about Esophagus is:
- The upper 2/3 of the esophagus contains striated muscle and is innervated by the vagus nerve (CNX). The lower 1/3 contains smooth muscle from splanchnic mesoderm and is innervated by the splanchnic plexus
- The lower 2/3 of the esophagus contains striated muscle and is innervated by the vagus nerve (CNX). The upper 1/3 contains smooth muscle from splanchnic mesoderm and is innervated by the splanchnic plexus
- The upper 2/3 of the esophagus contains smooth muscle and is innervated by the vagus nerve (CNX). The lower 1/3 contains skeletal muscle from splanchnic mesoderm and is innervated by the splanchnic plexus
- The upper 2/3 of the esophagus contains striated muscle and is innervated by the splanchnic plexus. The lower 1/3 contains smooth muscle from splanchnic mesoderm and is innervated by the vagus nerve
Ans.1. The upper 2/3 of the esophagus contains striated muscle and is innervated by the vagus nerve (CNX). The lower 1/3 contains smooth muscle from splanchnic mesoderm and is innervated by the splanchnic plexus.
USMLE Case Scenario
The mesentery, a large fold of peritoneum, suspends the small intestine from the posterior abdominal wall. The base of the mesentery attaches to the posterior abdominal wall:
- To the right of the third lumbar vertebra and passes obliquely to the left and inferiorly to the right sacroiliac joint
- To the left of the third lumbar vertebra and passes obliquely to the left and inferiorly to the right sacroiliac joint
- To the right of the second lumbar vertebra and passes obliquely to the left and inferiorly to the right sacroiliac joint
- To the left of the second lumbar vertebra and passes obliquely to the right and inferiorly to the right sacroiliac joint
Ans.4. To the left of the second lumbar vertebra and passes obliquely to the right and inferiorly to the right sacroiliac joint.
The mesentery contains blood vessels, nerves, lymphatics, and lymph nodes, as well as considerable fat. It attaches to the small intestine along the length of one side, the mesenteric border, leaving the remainder of the surface of the bowel covered by its visceral peritoneum, the serosa. The broad-based attachment of the mesenteric base stabilizes the small bowel and prevents it from twisting upon its blood supply.
USMLE Case Scenario
USMLE Case Scenario
During an abdomino pelvic surgery a big, tortuous vessel was seen by a gynecologist on the lateral side of uterus. The vessel was found to be a branch of internal iliac artery. Most likely the vessel found by the gynecologists was:
- Splenic artery
- Ovarian artery
- Vaginal artery
- Uterine artery
Ans.4. Uterine artery
USMLE Case Scenario
A surgeon wishes to perform a splenectomy on a 77-year-old patient who has been in an automobile accident. Before removing the spleen, the splenic artery and splenic vein are ligated. Within which of the following peritoneal structures are the splenic artery and vein found?
- Gastrocolic ligament
- Gastrosplenic ligament
- Lesser omentum
- Splenorenal ligament
Ans.4. Splenorenal ligament
USMLE Case Scenario
A 44-year-old has a normal thyroid gland which normally moves with swallowing because the thyroid gland is enclosed by which of the following fascia?
- Carotid sheath
- Investing layer of the deep cervical fascia
- Pretracheal fascia
- Prevertebral fascia
Ans.3. Pretracheal fascia
USMLE Case Scenario
A 15-year-old typist from ilinos comes to the health clinic because of recurrent episodes of wheezing during basketball practices. His activity has been hampered by shortness of breath shortly after beginning practice and during games. The symptoms are accompanied by a nonproductive cough and chest tightness. He denies any symptoms at rest. The symptoms occur whether the practices are indoors or outdoors. On physical examination, he is comfortable and denies any symptoms. His physical examination is unremarkable. Which of the following cells are most likely to mediate his symptoms?
- Eosinophils
- Lymphocytes
- Mast cells
- Monocytes
- Neutrophils
This patient has symptoms of exercise-induced asthma. The symptoms of exercise-induced asthma are due to mast cell release of histamines, which degranulate with the initiation of exercise.
USMLE Case Scenario
Carotid Sheath is an important structure. It contains a cranial nerve. The cranial nerve is:
- IX
- X
- XI
- XII
Ans.2. X
USMLE Case Scenario
The cranial nerve passing through the substance of parotid gland is:
- Abducens
- Facial
- Optic
- Trigeminal
- Glossopharyngeal
- Vagus
Ans.2. Facial
USMLE Case Scenario
A feature of Sharipos Syndrome is agenesis of:
- Corpus callosum
- Anterior commisure
- Posterior commisure
- Hippocampal commisure
Ans. 1. Corpus callosum
USMLE Case Scenario
During cranial nerve examination, a neurologist asks her 33-year-old patient to protrude his tongue. On doing so, her tongue deviates to the right side. This finding results from paralysis of tongue muscle namely:
- Genioglossus
- Styloglossus
- Palatoglossus
- Hyoglossus
Ans.1. Genioglossus
The genioglossus muscle is innervated by the hypoglossal nerve. The function of the genioglossus muscle is to pull the tongue forward (protrude) and toward the opposite side. When the right genioglossus muscle is paralyzed, the left genioglossus muscle pulls the tongue forward and to the right.
USMLE Case Scenario
Bells Palsy is a LMNL of a cranial nerve. The cranial nerve most commonly involved is:
- Abducens
- Facial
- Optic
- Trigeminal
Ans.2. Facial
USMLE Case Scenario
95An inflammatory process in the temporal bone has resulted in a swelling of the facial nerve within the facial canal. Which muscle maybe paralyzed as a result of this compression?
- Anterior belly of the digastrics
- Geniohyoid
- Stapedius
- Stylopharyngeus
Ans.3. Stapedius
The stapedius muscle is innervated by the facial nerve. This muscle is located in the middle ear and attaches to the neck of the stapes. Contraction of the Stapedius reduces the amplitude of oscillation of the stapes and thus reduces the perceived loudness of a sound. Paralysis of this muscle may result in hyperacusis.
USMLE Case Scenario
A 34-year-old male smoker notices loss of taste sensation in his anterior part of tongue. He reports to a physician who tells him that one of his nerves maybe damaged which supplies taste sensation to this part of his tongue. The nerve specifically most likely to be damaged is:
- Glossopharyngeal
- Lingual
- Chorda tympani
- Vagus
Ans.3. Chorda tympani
USMLE Case Scenario
The neck of the pancreas links the head and body. It is often the most anterior portion of the gland. The lower part of the neck lies anterior to the superior mesenteric vein. This is important during surgery for pancreatic cancer since malignant involvement of these vessels may make resection impossible. The anterior surface of the neck is covered with peritoneum. The posterior surface of neck is closely related to:
- Pylorus of stomach
- Aorta
- Internal iliac vein
- External iliac vein
- Common iliac vein
- Portal vein
Ans.6. Portal vein
The neck of the pancreas is defined as that portion of the pancreas which lies anterior to the portal vein, and is closely related to the upper posterior surface. The lower part of the neck lies anterior to the superior mesenteric vein just before the formation of the portal vein.
USMLE Case Scenario
An ENT surgeon plainly tells his patient from North Carolina that he has got hyperacusis and that one of his important nerve is damaged. The nerve most likely to be damaged is:
- Auriculotemporal
- Greater Auricular
- Auricular branch of Vagus
- Nerve to Stapedius
Ans.4. Nerve to Stapedius
USMLE Case Scenario
A 66-year-old patient from Ohio has a large meningioma involving the parasagittal region and falx cerebri neurologic deficits expected to be produced by mass lesion in this region is:
Ans.1. Lower limb paralysis
A meningioma of the parasagittal region and the falx cerebri would be located superiorly, between the two hemispheres. In this position, it could compress the sensory (postcentral gyrus) or motor cortex (precentral gyrus) supplying the lower extremities and cause lower limb paralysis.
USMLE Case Scenario
A 66-year-old man working in a bar complains of trouble swallowing and hoarseness. On physical exam, he is noted to have ptosis and a constricted pupil on the left, and a diminished gag reflex. Neurological examination shows decreased pain and temperature sensation on the left side of his face and on the right side of his body. Which vessel is most likely occluded?
- Spinal artery
- PICA
- AICA
- Vertebral artery
Ans.2. PICA
The signs and symptoms in this patient are consistent with occlusion of the posterior inferior cerebellar artery (PICA). PICA is a branch of the vertebral artery (which is itself a branch of the subclavian artery). Occlusion of PICA causes a lateral medullary syndrome characterized by deficits in pain and temperature sensation over the contralateral body (spinothalamic tract dysfunction); ipsilateral dysphagia, hoarseness, and diminished gag reflex (interruption of the vagal and glossopharyngeal pathways); vertigo, diplopia, nystagmus and vomiting (vestibular dysfunction); ipsilateral Horner’s syndrome (disruption of descending sympathetic fibers); and ipsilateral loss of pain and temperature sensation of the face (lesion of the spinal tract and nucleus of the trigeminal nerve).
USMLE Case Scenario
Vessel lying within cavernous sinus is:
- Internal carotid
- External carotid
- Common carotid
- External jugular vein
Ans.1. Internal carotid
USMLE Case Scenario
A 55-year-old male received a hit on left hypochondriac region. Spleen was found to be lacerated. On operation, a large tortuous vessel was found to be seen. Doctor reported it as splenic artery. It is a branch of:
- Celiac trunk
- Superior mesenteric artery
- Inferior mesenteric artery
- Thoracic aorta
Ans.1. Celiac trunk
USMLE Case Scenario
A 55-year-old male had a surgery. His leino renal ligament was seen to contain an artery. Most likely the artery was:
- Short gastric artery
- Splenic artery
- Pancreatic artery
- Renal artery
Ans.2. Splenic artery
USMLE Case Scenario
A 55-year-old is to be operated for inguinal hernia. An antomist while discussing the hernia describes one artery as a land mark for differentiating direct and indirect inguinal hernias. The artery most likely is:
- Superior epigastric artery
- Inferior epigastric artery
- Umbilical artery
- Obliterated umbilical artery
Ans. 2. Inferior epigastric artery
Remember:
Indirect inguinal hernias lie lateral to the inferior epigastric artery, whereas direct inguinal hernias lie medial to these vessels.
USMLE Case Scenario
The superficial perineal fascia is a continuation into the perineum of the membranous fascia from the anterior abdominal wall. The superficial perineal fascia is called as:
- Colles fascia
- Fascia colli
- Campers fascia
- Waldeyers fascia
- Thoraco lumbar fascia
Ans.1. Colles fascia
USMLE Case Scenario
An aneurysm of the axillary artery within the axilla is most likely to compress which of the following neural structures?
- Axillary nerve
- Long thoracic nerve
- Lower trunk of the brachial plexus
- Medial cord of the brachial plexus
Ans. 4. Medial cord of the brachial plexus
Remember:
Within the axilla, the axillary artery is within the axillary sheath and is surrounded by the three cords of the brachial plexus, which are also within the axillary sheath. An aneurysm of the axillary artery may compress any of the three cords.
USMLE Case Scenario
Physical examination of 32-year-old medical graduate from kansas reveals a winged left scapula and an inability to raise his left arm above the horizontal. Which of the following nerves is most likely affected?
- Axillary nerve
- Long thoracic nerve
- Lower subscapular
- Suprascapular nerve
Ans.2. Long thoracic nerve
Remember:
The serratus anterior, innervated by the long thoracic nerve, is responsible for stabilization of the scapula during abduction of the arm from 90 to 180 degrees. When the long thoracic nerve is damaged, it is difficult to elevate the arm above the horizontal. This nerve arises from C5, 6, and 7. Remember: ‘winged scapula’ is a classic clue for long thoracic nerve injury.
USMLE Case Scenario
Waldeyer’s ring is a circumpharyngeal ring of mucosa-associated lymphoid tissue which surrounds the openings into the digestive and respiratory tracts. It is made-up:
- Posterosuperiorly by the lingual tonsil
- Posteroinferiorly by the lingual tonsil
- Anteroinferiorly by the lingual tonsil
Ans.4. Anteroinferiorly by the lingual tonsil
Waldeyers Ring: Anteroinferiorly by the lingual tonsil, laterally by the palatine and tubal tonsils, and posterosuperiorly by the nasopharyngeal tonsil
USMLE Case Scenario
A 33-year-old female engineer complains to her orthopedician that her thumb does not work right. The physician notes weakness of the thumb in extension, although rotation, flexion, abduction, adduction, and opposition are normal. Which of the following nerves is most likely involved?
- Ulnar
- Radial
- Median
- Axillary
Ans.2. Radial
- Redial extension is provided by the extensors pollicis longus and brevis, which are innervated by the radial nerve
- The median nerve supplies the thenar group, which allows the thumb to oppose, flex, abduct, and rotate
- The ulnar nerve supplies the adductor pollicis, which adducts the thumb
- Axillary nerve supplies Teres Minor and Deltoid.
USMLE Case Scenario
A branch of the posterior cord of the brachial plexus particularly susceptible to injury in shoulder dislocations that displace the humeral head with impaired Arm abduction and loss of sensation over the lower half of the deltoid. The nerve involved is:
- Ulnar
- Radial
- Median
- Axillary
Ans.4. Axillary
USMLE Case Scenario
A nerve innervates the muscle of the anterior compartment of the arm but does not innervate any muscle in the hand is:
- Ulnar
- Radial
- Musculocutaneous
- Median
Ans.3. Musculocutaneous
USMLE Case Scenario
A 36-year-old Acromegaly patient complains of a tingling sensation in the 1st, 2nd, and 3rd digits of the right hand and loss of coordination and strength of the right thumb. The condition is most likely to be:
- Claw hand
- Carpal tunnel syndrome
- Ape hand deformity
- Dupynterns contracture
Ans.2. Carpal tunnel syndrome
Overgrowth in the wrist area has compressed the carpal tunnel, thereby impinging on the median nerve. The median nerve (root C5-T1) provides motor innervation to the forearm flexors, thenar muscles, and radial lumbricals. It provides sensory innervation to the radial 2/3 of the palm, volar surfaces of the thumb, 2nd and 3rd digits, and radial 1/2 of the 4th digit.
USMLE Case Scenario
A 55-year-old suffered trauma to his penis. His Dorsal artery of penis got damaged. The said vessel is a branch of:
- Anterior division of internal iliac artery
- Posterior division of internal iliac artery
- Anterior division of external iliac artery
- Posterior division of external iliac artery
Ans.1. Anterior division of internal iliac artery
The internal pudendal is a branch of the anterior division of the internal iliac artery. It gives rise to the inferior rectal artery, perineal artery, artery of the bulb in men, urethral artery, deep artery of the penis and dorsal artery of the penis.
USMLE Case Scenario
A 66-year-old reports pain in his left upper extremity and tingling and numbness in his 4th and 5th digits of his left hand. There is mild swelling of the left hand. The man reports most of his pain and numbness occurs when he is doing electric work with his arms overhead. X-ray reveals the presence of a cervical rib. The artery liable to be compressed is:
- Axillary
- Radial
- Brachial
- Subclavian
Ans.4. Subclavian
The subclavian artery passes laterally over the upper surface of the first rib and lies posterior to the scalenus anterior. In the case of thoracic outlet syndrome, this artery is usually compressed between the scalenus anterior and a cervical rib. Thoracic outlet syndrome is a broad term for a group of disorders in which there is compression of certain neurovascular bundles. The presence of a cervical rib adds to the compression, and repetitive motion and poor posture are other predisposing factors. When the neurovascular bundle is entrapped, the patient presents with neurological and/or circulatory changes in the upper extremity on the involved side.
USMLE Case Scenario
A 44-year-old complains of Galactorrhea and Amonorrhea. CT Scan was done. Image shows a pituitary tumor compressing optic chiasma. Hemianopia produced would be of type:
- Bitemporal hemianopia
- Binasal hemianopia
- Unilateral hemianopia
- Superior quadrant unilateral hemianopia
Ans.1. Bitemporal hemianopia
USMLE Case Scenario
The person shown in figure has features as identified in figure. Most likely he is suffering from a disease that affects which part of CNS.
- Cerebellum
- Substantia nigra
- Nucleus basalis
- Frontal lobe
Ans.2. Substantia nigra
USMLE Case Scenario
The chorda tympani nerve of is a branch of cranial nerve. The cranial nerve is:
- Abducens
- Facial
- Optic
- Trigeminal
Ans.2. Facial
USMLE Case Scenario
A 45-year-old from India notices swelling in his groin. He is reported to have an abscess after further investigations reveal tuberculosis of spine. The abscess is found along sheath of a muscle whose function is: to flex the thigh at the hip. The muscle involved is:
- Gluteus maximus
- Psoas
- Gluteus minimus
- Sartorius
Ans.2. Psoas
USMLE Case Scenario
Pyramidalis is a triangular muscle that lies in front of the lower part of rectus abdominis within the rectus sheath. It is attached by tendinous fibers to the front of the pubis and to the ligamentous fibers in front of the symphysis. The muscle diminishes in size as it runs upwards, and ends in a pointed apex that is attached medially to the linea alba. This attachment usually lies midway between the umbilicus and pubis, but may occur higher. The pyramidalis is supplied by:
- The terminal branches of the subcostal nerve
- The terminal branches of the iliohypogastric nerve
- The terminal branches of the ilioinguinal nerve
- The terminal branches of the genitofemoral nerve
Ans.1. The terminal branches of the subcostal nerve
USMLE Case Scenario
The muscles of the pharynx with the exception of one muscle are supplied from the pharyngeal plexus by the pharyngeal branch of the vagus. The exception is:
- Palatopharyngeus
- Stylopharyngeus
- Salpingopharyngeus
- Inferior constrictor
Ans. 2. Stylopharyngeus
The muscles of the pharynx-with the exception of stylopharyngeus, which is supplied by the glossopharyngeal nerve are supplied from the pharyngeal plexus by the pharyngeal branch of the vagus. This branch emerges from the upper part of the inferior vagal ganglion.
USMLE Case Scenario
The paired renal arteries supply the kidneys through a number of subdivisions described sequentially as segmental, lobar, interlobar, and arcuate arteries. These are end arteries with no anastomoses. The renal arteries branch laterally from the:
- Iliac vessels just below the origin of the superior mesenteric artery
- Iliac vessels just above the origin of the superior mesenteric artery
- Aorta just below the origin of the superior mesenteric artery
Ans.3. Aorta just below the origin of the superior mesenteric artery
The renal arteries branch laterally from the aorta just below the origin of the superior mesenteric artery. Both cross the corresponding crus of the diaphragm at right angles to the aorta. The right renal artery is longer and often higher, passing posterior to the inferior vena cava, right renal vein, head of the pancreas and descending part of the duodenum. The left renal artery is a little lower and passes behind the left renal vein, the body of the pancreas and splenic vein.
USMLE Case Scenario
The aortic aperture is the lowest and most posterior of the large openings. It is at the level of the lower border of the twelfth thoracic vertebra and the thoracolumbar intervertebral disk, slightly to the left of the midline. It is an osseoaponeurotic opening defined by the diaphragmatic crura laterally, the vertebral column posteriorly and the diaphragm anteriorly. Strictly speaking, it lies behind the diaphragm and its median arcuate ligament. The aortic opening transmits:
- The aorta, thoracic duct, azygos veins
- The inferior vena cava, thoracic duct, azygos veins
- Esophagus, thoracic duct, azygos veins
- The phrenic nerve, thoracic duct, azygos veins
Ans.1. The aorta, thoracic duct, azygos veins
USMLE Case Scenario
The epithelial lining of the trachea is composed of:
- Pseudostratified columnar nonciliated cells, goblet cells and basal cells
- Pseudostratified columnar ciliated cells, goblet cells and basal cells
- Stratified columnar nonciliated cells, goblet cells and basal cells
- Stratified noncolumnar ciliated cells, goblet cells and basal cells
Ans.2. Pseudostratified columnar ciliated cells, goblet cells and basal cells
USMLE Case Scenario
Kidney is surrounded by a special layer of fascia called:
- Waldeyers fascia
- Fascia coli
- Denonveliers fascia
- Gerota’s fascia
- Cruveilhier’s fascia
- Camper’s fascia
- Colles’ fascia
- Scarpa’s fascia
Ans.4. Gerota’s fascia
USMLE Case Scenario
The ovarian vessels follow a downward course and pass between the layers of the infundibulopelvic ligament and the broad ligament to reach the ovary. The true statement regarding blood supply of ovary is:
- The ovarian arteries arise from aorta, the left ovarian vein and the right ovarian vein empties into the vena cava
- The ovarian arteries arise from aorta and the left ovarian vein empties into the left renal vein; the right ovarian vein empties into the vena cava
- The ovarian arteries arise from uterine artery and the right ovarian vein empties into the left renal vein; the left ovarian vein empties into the vena cava
- The ovarian arteries arise from uterine artery and the left ovarian vein empties into the left renal vein; the right ovarian vein empties into the vena cava
Ans.2. The ovarian arteries arise from aorta and the left ovarian vein empties into the left renal vein; the right ovarian vein empties into the vena cava.
USMLE Case Scenario
A 44-year-old suffers fracture of surgical neck of humerus. Most likely effected nerve is:
- Radial
- Musculocutaneous
- Ulnar
- Anterior interosseous c nerve
- Cranial nerve XI
- Subscapular
- Axillary nerve
Ans.7. Axillary nerve
USMLE Case Scenario
Valves of Kerckring are seen in:
- Appendix
- Small intestine
- Cecum
- Sigmoid colon
- Rectum
- Anal canal
Ans.2. Small intestine
The mucosal surface of the small intestine contains numerous circular mucosal folds called the plicae circulares (valvulae conniventes, or valves of Kerckring). These folds are 3 to 10 mm in height; they are taller and more numerous in the distal duodenum and proximal jejunum, becoming shorter and fewer distally. Intestinal villi barely visible to the naked eye resemble tiny finger-like processes projecting into the intestinal lumen.
USMLE Case Scenario
A nerve innervates the anconeus muscle of the arm. Most likely nerve supply of anconeus is:
- Ulnar
- Radial nerve
- Musculocutaneous
- Median
Ans.2. Radial nerve
USMLE Case Scenario
The cranial nerves lying in the cavernous sinus are:
- VII, IX
- X, XI
- XII, VI
- Divisions of V nerve
- Divisions of VII nerve
Ans.4. Divisions of V nerve
USMLE Case Scenario
Annular bronchial cartilage is congenitally absent, leading to bronchomalacia and Bronchiectasis is termed as:
- Cystic fibrosis syndrome
- Ehlers-Danlos syndrome
- Mounier-Kuhn syndrome
- Kartageners syndrome
- Immotile cilia syndrome
- Williams-Campbell syndrome
Ans.6. Williams-Campbell syndrome
USMLE Case Scenario
Fold of serous pericardium surrounding right and left pulmonary veins are connected by an irregular pericardial reflection creates a space termed the:
- Oblique sinus
- Transverse sinus
- Coronary sinus
Ans.1. Oblique sinus
USMLE Case Scenario
After a fight a sharp instrument passed through the superior orbital fissure of a 45-year-old man. It would most likely damage the:
- Abducens nerve
- Facial nerve
- Mandibular nerve
- Maxillary nerve
- Middle meningeal artery
- Ophthalmic artery
- Optic nerve
Ans.1. Abducens nerve
Almost everything that innervates the eye, other than the optic nerve, passes through this fissure. This includes the oculomotor nerve (CN III), the trochlear nerve (CN IV), the ophthalmic nerve (V1), and the abducens nerve (CN VI).
USMLE Case Scenario
Meckel’s Diverticulitis is persistence of:
- Portion of the vitelline duct on the mesenteric border of the distal ileum, may produce bleeding, intestinal obstruction
- Portion of the vitelline duct on the mesenteric border of the proximal ileum, may produce bleeding, intestinal obstruction
- Portion of the vitelline duct on the antimesenteric border of the proximal ileum, may produce bleeding, intestinal obstruction
- Portion of the vitelline duct on the antimesenteric border of the distal ileum, may produce bleeding, intestinal obstruction
Ans.4. Portion of the vitelline duct on the antimesenteric border of the distal ileum, may produce bleeding, intestinal obstruction
USMLE Case Scenario
A 27-year-old woman presents with hyperthyroidism, and subtotal thyroidectomy is successfully performed, but following the surgery, the woman is extremely hoarse, and can barely speak above a whisper. This hoarseness is most probably related to damage to a nerve which is a branch of CRANIAL NERVE:
- IX
- X
- XI
- XII
Ans.2. X
USMLE Case Scenario
A physician is performing a cranial nerve examination on a patient. While testing the gag reflex, it is noted that when the right side of the pharyngeal mucosa is touched, the patient’s uvula deviates to the right. When the left side of the pharyngeal mucosa is touched, the patient does not gag. Which of the following is the most likely location of his lesion?
- Left glossopharyngeal nerve and left vagus nerve
- Right glossopharyngeal nerve and left vagus nerve
- Left glossopharyngeal nerve and Right vagus nerve
- Right glossopharyngeal nerve and Right vagus nerve
Ans.1. Left glossopharyngeal nerve and left vagus nerve
USMLE Case Scenario
A cranial nerve innervates the stylopharyngeus muscle and the parotid gland. Visceral afferents supply the carotid sinus baroreceptors and carotid body chemoreceptors, and mediate taste from the posterior one-third of the tongue. Somatosensory fibers supply pain, temperature, and touch information from the posterior one-third of the tongue, upper pharynx, middle ear and eustachian tube. The cranial nerve mentioned is:
- IX
- X
- XI
- XII
Ans.1. IX
USMLE Case Scenario
An injury to the lateral portion of the dorsal columns would most likely damage:
- Fine motor control of fingers
- Motor control of the contralateral foot
- Sweating of the ipsilateral face
- Proprioception from the ipsilateral leg
- Vibratory sense from the ipsilateral arm
- Vibratory sense from the contralateral arm
- Sensory control of the contralateral foot
Ans. 5. Vibratory sense from the ipsilateral arm
USMLE Case Scenario
Atresia (blockage) of this canal results from failure of the meatal plug to canalize. Usually the deep part of the meatus is open, but the superficial part is blocked by bone or fibrous tissue. Most cases are associated with the:
- First arch syndrome
- Second arch syndrome
- Third arch syndrome
- Fifth arch syndrome
Ans.1. First arch syndrome
USMLE Case Scenario
The tensor tympani muscle, attached to the malleus, is derived from mesenchyme in the first pharyngeal arch and is innervated by:
- CN V, the nerve of this arch
- CN VI, the nerve of this arch
- CN VII, the nerve of this arch
- CN VIII, the nerve of this arch
Ans.1. CN V, the nerve of this arch
USMLE Case Scenario
Fine motor control of the fingers would be carried principally by the:
- Contralateral lateral corticospinal tract
- Ipsilateral lateral corticospinal tract
- Ipsilateral rubrospinal tract
- Ipsilateral Tectospinal tract
- Ipsilateral vestibulospinal tract
Ans.2. Ipsilateral lateral corticospinal tract
USMLE Case Scenario
The rectum is separated from the prostate by:
- Waldeyers fascia
- Fascia coli
- Denonveliers fascia
- Gerota’s fascia
- Cruveilhier’s fascia
- Camper’s fascia
- Colles’ fascia
- Scarpa’s fascia
Ans.3. Denonveliers fascia
USMLE Case Scenario
An 89 years old elderly patient suffering from Picks disease also had multiple small strokes. During her stay in the nursing home on multiple occasions she aspirated food, and neurological examination reveals that her gag reflex is absent. These findings suggest involvement of the nucleus of which of the following cranial nerves?
- Facial (VII)
- Glossopharyngeal (IX)
- Hypoglossal (XII)
- Spinal accessory (XI)
- Vestibulocochlear (VIII)
Ans.2. Glossopharyngeal (IX)
Cranial nerve IX is the glossopharyngeal nerve, which has a nucleus in the medulla and is necessary for the gag reflex
USMLE Case Scenario
The esophagus begins at the lower border of the cricoid cartilage at the level of C6 vertebra. It is about 25 cm (10 inches) long. The intra-abdominal part of the esophagus varies in length according to the tone of its muscle and the degree of distension of the stomach. It passes through the diaphragm at the level of:
- T6 vertebra
- T8 vertebra
- T10 vertebra
- T12 vertebra
Ans.3. T10 vertebra
USMLE Case Scenario
The upper part of the anal canal above the pectinate line is endodermal, and the lower part is derived from the ectoderm. The upper half of the canal is lined by columnar epithelium and the lower half with stratified squamous epithelium. True statement would be:
- A carcinoma of the lower canal is usually an adenocarcinoma, while that arising from the upper part would be a squamous cell carcinoma
- A carcinoma of the upper canal is usually an adenocarcinoma, while that arising from the lower part would also be an adenocarcinoma
- A carcinoma of the upper canal is usually a squamous cell carcinoma, while that arising from the lower part would also be a squamous cell carcinoma
- A carcinoma of the upper canal is usually an adenocarcinoma, while that arising from the lower part would be a squamous cell carcinoma
Ans.4. A carcinoma of the upper canal is usually an adenocarcinoma, while that arising from the lower part would be a squamous cell carcinoma
USMLE Case Scenario
The cranial nerve carrying the pain sensations from tip of tongue is:
- VI
- V2
- V3
- VII
- IX
- X
- XI
- XII
Ans.3. V3
The mandibular division of the trigeminal nerve (V3) carries general somatic sensation from the anterior two-thirds of the tongue.
USMLE Case Scenario
Which of the following eye muscles rotates the eye downward and away from midline?
- Inferior oblique
- Superior oblique
- Inferior rectus
- Superior rectus
Ans.2. Superior oblique
USMLE Case Scenario
A 44-year-old engineer noticed that he has an eye that is persistent directed toward his nose. A lesion of which of the following nerves could produce this finding?
- CN II
- CN IV
- CN V
- CN VI
Ans.4. CN VI
USMLE Case Scenario
The Fascial layer separating the rectum from the coccyx is:
- Waldeyers fascia
- Fascia coli
- Denonveliers fascia
- Gerota’s fascia
- Cruveilhier’s fascia
- Camper’s fascia
- Colles’ fascia
- Scarpa’s fascia
Ans.1. Waldeyers fascia
USMLE Case Scenario
Carotid Sheath is an important structure. It contains:
- Facial nerve and internal carotid artery
- Facial nerve and external carotid artery
- Facial artery and external carotid artery
- Vagus nerve and external carotid artery
- Vagus nerve and internal carotid artery
Ans.5. Vagus nerve and internal carotid artery
USMLE Case Scenario
Meckels ganglion is related to a cranial nerve. The cranial nerve is:
- Abducens
- Facial
- Optic
- Trigeminal
Ans.4. Trigeminal
USMLE Case Scenario
The cranial nerve supplying the Trapezius muscle is:
- VII
- IX
- X
- XI
- XII
Ans.4. XI
USMLE Case Scenario
A Nerve innervating the muscles of the Posterior compartment of the arm is:
- Ulnar
- Radial
- Musculocutaneous
- Median
Ans.2. Radial
USMLE Case Scenario
Physical examination of 36-year-old medical graduate from Texas reveals a winged left scapula and an inability to raise his left arm above the horizontal. Which of the following muscles is most likely affected?
- Serratus posterior
- Serratus anterior
- Deltoid
- Scalenus anterior
- Scalenus medius
- Scalenus posterior
- Levator scapulae
- Sternomastoid
- Rhombidius minor
Ans.2. Serratus anterior
Remember:
The serratus anterior, innervated by the long thoracic nerve, is responsible for stabilization of the scapula during abduction of the arm from 90 to 180 degree.
USMLE Case Scenario
A Newborn boy does not pass meconium until 55 hours after his birth. Several weeks later his mother complains that he has not been passing stool regularly. Anorectal manometry reveals increased internal anal sphincter pressure on rectal distention with a balloon. The patient’s disorder is:
- Intussusception
- Hirschsprungs disease
- Exomphalos
- Dysphagia lusoria
- Anal atresia
- Malrotation of gut
Ans.2. Hirschsprungs disease
USMLE Case Scenario
A physician during cranial nerve examination asks her patient to protrude his tongue. On doing so, her tongue deviates to the right side. This finding results from paralysis of tongue muscle. The likely nerve paralyzed is:
- Facial
- Vagus
- Hypoglossal
- Glossopharyngeal
- Chorda tympani
- Lingual
Ans. 3. Hypoglossal
The genioglossus muscle is innervated by the hypoglossal nerve. The function of the genioglossus muscle is to pull the tongue forward (protrude) and toward the opposite side. When the right genioglossus muscle is paralyzed, the left genioglossus muscle pulls the tongue forward and to the right.
USMLE Case Scenario
As part of a complete neurological examination, a medical student takes a cotton-tipped applicator and touches the patient’s left eye with a thin wisp of cotton as the patient looks to the right. The patient closes both of his eyelids in response. Which of the following cranial nerves is responsible for the sensory limb of this reflex?
- Abducens
- Facial
- Optic
- Trigeminal
Ans.4. Trigeminal
USMLE Case Scenario
A 34-year-old patient arrives in the emergency room after having suffered severe head trauma in a accident. Radiographic studies of the head reveal a basilar skull fracture in the region of the foramen ovale. Which of the following nerve passes through this foramen:
Ans.2. Mandibular
USMLE Case Scenario
Annular pancreas is a condition that results when normal pancreatic tissue completely or partially encircles the duodenum. Annular pancreas is thought to arise from failure of normal clockwise rotation of the ventral pancreatic bud. In children, there is a common association with other serious congenital anomalies such as intracardiac defects, Down’s syndrome, and intestinal malrotation. It commonly encircles:
- First part of duodenum
- Second part of duodenum
- Third part of duodenum
- Fourth part of duodenum
- Jujenum
- Ileum
Ans.2. Second part of duodenum
USMLE Case Scenario
Pancreas is a mixed gland divided into four portions: the head, the neck, the body, and the tail. It is a retroperitoneal organ. The structure related to the head of the pancreas is:
- Hilum of spleen
- Uncinate process
- Portal vein
- Tuber omentale
- Pappilary process
- Foramen of Winslow
- Ligament of Treitz
- Linea semilunaris
Ans.2. Uncinate process
USMLE Case Scenario
The Distal portion of the gallbladder has the appearance of a diverticulum, which is called:
- Morrisons pouch
- Zenkers diverticulum
- Meckel’s diverticulum
- Spiral valve of Heister
- Hartmann’s pouch
- Uncinate process
- Tuber omentale
- Pappilary process
- Foramen of Winslow
Ans.5. Hartmann’s pouch
USMLE Case Scenario
Pancreas is a mixed gland divided into four portions: the head, the neck, the body, and the tail. It is a retroperitoneal organ. The endocrine portion of pancreatic function is served by the structures termed the islets of Langerhans. The islets are nearly spherical collections of cells scattered throughout the pancreatic parenchyma and is composed of several distinctive cell types. True statement is:
- The insulin-producing alpha cells compose the majority of the islet population
- The insulin-producing beta cells compose the majority of the islet population
- The insulin-producing alpha cells compose the minority of the islet population
Ans.3. The insulin-producing beta cells compose the majority of the islet population
USMLE Case Scenario
Embryologically, the gut rotates and the rotation occurs in a way that:
- The large intestine rotates in a clockwise manner around the axis of the celiac trunk
- The large intestine rotates in a clockwise manner around the axis of the superior mesenteric artery
- The large intestine rotates in a clockwise manner around the axis of the inferior mesenteric artery
- The large intestine rotates in a counterclockwise manner around the axis of the celiac trunk
- The large intestine rotates in a counterclockwise manner around the axis of the superior mesenteric artery
- The large intestine rotates in a counterclockwise manner around the axis of the inferior mesenteric artery
Ans.5. The large intestine rotates in a counterclockwise manner around the axis of the superior mesenteric artery
USMLE Case Scenario
The ligaments that should be carefully considered during mobilization of the splenic flexure to avoid injury to the spleen are:
- Leinorenal and splenocolic attachments
- Phrenocolic and leinorenal attachments
- Phrenocolic and splenocolic attachments
- Greater omentum and splenocolic attachments
- Lesser omentum and leinorenal attachments
Ans.3. Phrenocolic and splenocolic attachments
The large intestine rotates in a counterclockwise manner around the axis of the superior mesenteric artery
USMLE Case Scenario
The anastomosis between the superior and inferior mesenteric vessels is known as the:
- Marginal artery of Drumond
- Sudecks point
- Batesons Plexus
- Vasa recta
- Anastomosis of Riolan
Ans.5. Anastomosis of Riolan
USMLE Case Scenario
As Per the anatomical knowledge of a student, which is not true about pain:
- A sudden burning pain in the epigastric region suggests a perforated viscus
- Severe intermittent cramping pain with short pain-free intervals favors small bowel obstruction
- Sudden excruciating tearing pain maybe associated with a ruptured aneurysm
- Pain of acute cholecystitis frequently radiates around the right costal margin to the right scapula and to the shoulder
- Pain in acute pancreatitis is usually epigastric in origin, with subsequent radiation along both costal margins to the back
- Ureteral calculi causes pain radiating to the groin
- Pain of stomach is referred to perineum
Ans.7. Pain of stomach is referred to perineum
USMLE Case Scenario
Maximal tenderness in the right lower quadrant over Mcburney’s point is suggestive of an inflammation of an organ. The characteristic feature of the organ implicated is:
- It is rich in blood supply with rich anastomosis
- It is rich in lymphatic tissue
- It is a derivative of foregut
- It has a fixed location
- It has a wide lumen
Ans.3. It is rich in lymphatic tissue
USMLE Case Scenario
The arterial supply to the hypothalamic-pituitary region is complex and arises from three sources. The inferior hypophyseal artery, the superior hypophyseal arteries and the middle hypophyseal arteries. These vessels drain into the hypophyseal portal system, which forms a secondary venous plexus in the anterior pituitary and ultimately empties into the cavernous sinus. The inferior hypophyseal artery is:
- A branch of the internal carotid artery
- A branch of the external carotid artery
- A branch of the common carotid artery
- A branch of the vertebral artery
- A branch of the subclavian artery
Ans.1. A branch of the internal carotid artery
USMLE Case Scenario
Oxyphil cells are a feature of:
- Spleen
- Pituitary
- Adrenals
- Prostate
- Lens of eye
- Cochlea
- Thymus
- Thyroid
- Parathyroid
Ans.9. Parathyroid
USMLE Case Scenario
The superior parathyroid glands are usually located on the posterior surface of the upper portion of the thyroid lobe. The lower parathyroid glands are more ventral, close to the lower pole of the thyroid gland. True statement about the development of parathyroids is:
- The superior parathyroids arise from the second pharyngeal pouch and the inferior parathyroids arise from the third pharyngeal pouch
- The superior parathyroids arise from the second pharyngeal pouch and the inferior parathyroids arise from the fourth pharyngeal pouch
- The superior parathyroids arise from the third pharyngeal pouch and the inferior parathyroids arise from the fourth pharyngeal pouch
- The superior parathyroids arise from the fourth pharyngeal pouch and the inferior parathyroids arise from the third pharyngeal pouch
Ans.4. The superior parathyroids arise from the fourth pharyngeal pouch and the inferior parathyroids arise from the third pharyngeal pouch
USMLE Case Scenario
The transition between the oblique fibers of the thyropharyngeus muscle and the transverse fibers of the cricopharyngeus muscle creates a point of potential weakness in the pharyngoesophageal segment, which is the site of origin of:
Ans.3. Pharyngoesophageal diverticulum
USMLE Case Scenario
The esophagus is a hollow tube of muscle that is approximately 25 cm in length and extends from the pharynx to the stomach. It is arbitrarily divided into four segments: pharyngoesophageal, cervical, thoracic, and abdominal.
True statement about esophagus is that:
- The esophagus is a nonmucosal-lined muscular tube that has a serosa
- The esophagus is a nonmucosal-lined muscular tube that lacks a serosa
- The esophagus is a mucosal-lined muscular tube that has a serosa
- The esophagus is a mucosal-lined muscular tube that lacks a serosa
Ans.4. The esophagus is a mucosal-lined muscular tube that lacks a serosa
USMLE Case Scenario
Throughout the fat of the breast, coursing from the overlying skin to the underlying deep fascia, strands of dense connective tissue provide shape and hold the breast upward. These strands, devoid of epithelial elements, are called:
- Montogmerys tubercles
- Sappys Plexus
- Axillary tail of spence
- Cooper’s ligaments
- Milk line
- Pectoral fascia
Ans.4. Cooper’s ligaments
USMLE Case Scenario
Retropubic space is named after:
- Fallopius
- Meckel
- Camillo golgi
- Hunter
- Scarpa
- Retzius
- Tredlenburg
Ans.6. Retzius
USMLE Case Scenario
In the cochlear pathway, the axons terminate in the dorsal and ventral cochlear nuclei in the medulla and the pathway to the auditory cortex consists of at least four orders of neurons and includes the superior olivary complexes, the lateral lemnisci, the inferior colliculi, and the medial geniculate bodies. The auditory cortex:
- Lies in the posterior portion of the Inferior temporal gyrus
- Lies in the posterior portion of the superior temporal gyrus
- Lies in the posterior portion of the superior frontal gyrus
- Lies in the posterior portion of the middle frontal gyrus
- Lies in the posterior portion of the inferior frontal gyrus
Ans.2. Lies in the posterior portion of the superior temporal gyrus
USMLE Case Scenario
The primordia of the principal respiratory organs appear as a medial longitudinal groove in the ventral wall of the pharynx by the fourth week of gestation. True statement is:
- The tube is lined with ectoderm, from which the epithelium of the respiratory tract develops
- The tube is lined with mesoderm, from which the epithelium of the respiratory tract develops
- The tube is lined with endoderm, from which the epithelium of the respiratory tract develops
- The tube is lined with endothelium, from which the epithelium of the respiratory tract develops
- The tube is lined with mesothelium, from which the epithelium of the respiratory tract develops
Ans.3. The tube is lined with endoderm, from which the epithelium of the respiratory tract develops
USMLE Case Scenario
Folds of serous pericardium surrounding the entrance of the right and left pulmonary veins are connected by an irregular pericardial reflection that creates a space called as:
- Transverse sinus
- Oblique sinus
- Occipital sinus
- Maxillary sinus
- Coronary sinus
- Sinus of morgagni
- Sinus venosus
Ans.2. Oblique sinus
USMLE Case Scenario
The Mullerian ducts develop into the:
- Ovaries, uterus, cervix, and lower vagina
- Ovaries, uterus, cervix, and upper vagina
- Cervix, and upper vagina only
- Uterus, cervix, and upper vagina
- Fallopian tubes, uterus, cervix, and upper vagina
- Ovaries, fallopian tubes, uterus, cervix, and upper vagina
Ans.5. Fallopian tubes, uterus, cervix, and upper vagina
USMLE Case Scenario
A semicircular line which is about halfway between the umbilicus and pubic symphysis is named as line of:
- Mc Burney
- Nelaton
- Rion
- Douglas
- Waldeyer
- Morrison
- Heister
- Scarpa
- Zuckderkand
Ans.4. Douglas
USMLE Case Scenario
Lymphatics from the gallbladder drain into the lymph node, located near the superior aspect of the junction of the infundibulum of the gallbladder and the cystic duct. It is known as:
- Lymph node of Rossenmüller
- Lymph node of Cloquet
- Delphic node
- Lymph node of lund
Ans.4. Lymph node of lund