Definition of Anatomy
Anatomy is the science that deals with structural (morphological) arrangement of various components of an organ, tissue or part of the body and its correlation with function.
The word morphology is derived from Greek which means structure.
The word anatomy is derived from Greek “anatome” which means cutting up; ana = up, tome = cutting. Latin equivalent for anatomy is dissection. Dis = as under, secare = to cut. Cutting up of cadaver (dead body) is the method by which study of structure of living things is made possible.
Physiology is the study of functions of the body. Functions include digestion, respiration, circulation, reproduction, movement of lower limbs for walking and upper limbs for holding an object, etc. Structure and function are inseparable. Structural arrangement is based on function, and functional requirement decides the structural arrangement.
Biochemistry is the study of chemical processes involved in performing a function by the structure in a living organism.
Structure Contributing to Function
Structure plays an important role in function. For example, a building or a bridge is constructed keeping in mind its weight-bearing function (People, goods, etc.). Similarly, the structure of bones of skull and face differs from that of limb bones as their functions are different. The bones of skull and face are for lightening the head. The bones of limbs are for weight bearing.
Evolutionary Revolutions in Anatomy
From time immemorial, anatomy has been studied by methodically dissecting and observing the cadavers (dead bodies) that are preserved by injecting chemicals. The 2anatomical dissections are done region-wise and the various structures, their positions and relations are observed. Gross anatomy, microscopic anatomy (histology) and developmental anatomy (embryology) are the major subdivisions of such a study. Embryology is also studied by dissecting dead fetuses.
In the earlier times, the teaching and learning of anatomy was more of descriptive in nature. New breakthroughs in the field of medicine (imaging techniques, invasive procedures) have brought revolution in the teaching and learning of anatomy. At present, the descriptive anatomy needs to be learnt with a functional orientation and should form the basis for clinical application in the patient care. It is now possible to visualize internal structure without cutting open the body, even in a living individual. In fact, such techniques can be done properly if only there is sound knowledge of anatomy. Lacunae in anatomical knowledge while performing such techniques can lead to damage of structures and in turn, other complications. On the other hand, by using such techniques, knowledge of anatomy can be refined and intricate details can be added.
Importance of Anatomy
- Foundation for understanding health-related fields: Human anatomy is the foundation for students of health-related fields like medicine, nursing, dentistry, laboratory technology, and physician assistant courses. It can be better understood by visual observation of cadaveric dissections and pictures or photographs or colorful illustrations.
- Basis and clinical application: Anatomy is the basis for understanding structure and function of human body. Application of anatomical knowledge is required for understanding the clinical conditions, for planning and interpreting laboratory investigations and for planning and undertaking treatment procedures.
Subdivisions of Anatomy
For understanding the structure and its function in health and disease, the subject of anatomy can be studied under the following subdivisions.
- Gross anatomy or macroscopic anatomy: (Macro = large). A branch of anatomy for understanding the appearance of parts or organs and their relations with unaided eye. It is the study of organ systems, such as the nervous system, respiratory system, digestive system, etc. (Fig. 1.1A).
- Histology or microscopic anatomy: (Micro = small; histo = tissue). Study of structures that cannot be seen with the unaided eye. It requires the use of microscope (Fig. 1.1B).
- Embryology or developmental anatomy: Study of early developmental stages of an organism. Knowledge of embryology provides the basis for certain of the clinical conditions that might have resulted from errors during early developmental period of an organism. Embryology provides the basis for location and relations of the structure, e.g. location and relations of heart, liver, stomach, spleen, kidney, etc. (Fig. 1.1C).
- Radiographic anatomy or living anatomy: With the advancements in medicine, it is now possible to visualize internal structures in a living individual without opening the body. Various parts of body and organ systems can be visualized by X-rays, ultrasound, computed tomography (CT), magnetic resonance imaging (MRI), bronchoscopy, intravenous pyelography, etc. for understanding the normal appearance in health and for identifying the abnormality in disease. Sound anatomical knowledge is required for performing the technique and for interpretation of the structures visualized (Fig. 1.1D).
- Surface or topographic anatomy: This method can be used both on the cadavers and on the living individuals. This forms the basis for physical examination of a patient and for performing surgical procedures in clinical practice. In this method, internal structures of the body were studied by marking them on the surface of the cadaver or palpating them on the surface of the body like the liver, kidney, heart, etc. (Fig. 1.1E).
- Living anatomy: Study of anatomy in a living individual by using simple techniques like (Figs. 1.2A to D):
- Inspection: By visual observation, e.g. observing the movement of thyroid gland by asking a person to swallow wherein it moves up and down (Fig. 1.2A); observing the apex beat of the heart in a person with naked chest.
- Palpation: By feeling with the hand, e.g. feeling the apex beat of heart with your hand placed on the topographical location of apex of heart or feeling the radial pulse with your fingers by appropriately holding the topographical area where it can be felt near the wrist (Fig. 1.2B).
- Percussion: By tapping the surface of a body part with middle finger of one hand on the middle finger of other hand that was kept in contact with the body surface. Interpretation is by the resulting sound, i.e. a resonant note or a dull note. By this method, collection of fluid in the lung (pleural effusion) can be identified (Fig. 1.2C).
- Auscultation: By listening to the sounds arising within organs by using stethoscope, e.g. heart sounds, breath sounds and bowel sounds that aid in diagnosis and treatment (Fig. 1.2D).
- Clinical anatomy: Application of anatomical knowledge in the diagnosis and treatment of patients either by medical or by surgical methods. Surgical anatomy is the study of structures giving emphasis on its direct practical significance in the practice of surgery (Fig. 1.3).
- Comparative anatomy: Comparison of changes in the morphology and function of different organs and organ systems of the human body that has occurred during evolution from the fish to the mammalian stage.
- Physical or biological anthropology: A discipline that deals with physical, biological and behavioral aspects of human beings, their related nonhuman primates and their hominoid ancestors those are extinct. It is the study of human evolution. It focuses on origin, evolution and diversity of people of different race, ethnicity and sociocultural background.
- Human genetics: It is the study of heredity, the process of transmission of genes (characters or traits) from parents to offspring and associated variations that can play a role in the causation of defects or diseases.
Approaches for Studying Anatomy
The human body can be studied region-wise or system-wise for a logical understanding.
- Region-wise or regional anatomy: It is the study of one region of the body at a time and learning everything about that region. The regions of the body from head to foot are as shown in Table 1.1.
- System-wise or systemic anatomy: It is the study of one system at a time. For convenience of description and for easy understanding, it is divided into various systems as shown in Table 1.2.
Note: For a medical graduate, region-wise approach with a correlation of related systems and subdivisions is followed for a comprehensive understanding of the subject.
For other branches of medical field, a system-wise approach is followed giving emphasis on structures of importance for practicing their profession.
Anatomical Position and Planes
For visual orientation and for understanding of various structural arrangements of organs, the body has to be sectioned and studied along three fundamental planes, viz. sagittal, coronal and transverse. These descriptive planes and terms of direction are standardized with reference to anatomical position for maintaining uniformity in description, understanding and interpretation throughout the world by medical professionals. Adopting uniform medical terminology avoids confusion and ambiguity. Hence, all descriptions of the human body are made with reference to a standard position called the normal anatomical position (Fig. 1.4).6
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Anatomical Position
The relationship of one body part to the other body part of the human body is described by imagining as if the person standing in an artificial posture known as anatomical position which is used as a standard reference in medical profession.
In anatomical position, the body is imagined as described in Table 1.3 and Figure 1.4. Both in dissection of the cadaver or in examination of a living individual or during radiological imaging, two other positions frequently adopted are the supine and prone positions (Table 1.4 and Fig. 1.5A).
Various Positions of the Body are of Clinical Importance
For examination or for treatment purposes, certain other positions are adopted in clinical practice. They are right or left lateral, Trendelenburg, Fowler, Sims, etc. (Table. 1.4 and Figs. 1.5B to G).
Anatomical Planes
Anatomical planes describe the sectional views of a part of body or an organ. They help in understanding the relationship of one organ with the other and structural orientation of tissue. These are useful in radiology and in sectioning tissues for histological examination.7
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They help in understanding the basic movements that take place along these planes.
The descriptive planes used to describe the location of a structure or organ and the movements along these planes are represented in Table 1.5 and Figures 1.6A to D.
Anatomical Terminology
The importance of language of medical field to the students of that profession is for communicating with their professional colleagues and for understanding the subject. Scientific medical term is a word that gives information about a structure in the body or a process that takes place in an organ, organ system and organism. Some scientific terms have two or three different parts. These parts are known as:
- Prefix
- Root (or base)
- Suffix
Examples:
- Subcutaneous
- Sub = below (prefix)
- Cutis = skin (root)
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Table 1.5 Anatomical planes. PlaneDescriptionFigs. 1.6A to D: Anatomical planes.Sagittal plane- It is an imaginary vertical plane
- It passes through the center of the body
- By cutting along this plane, the body can be divided into two identical halves, i.e. right and left half
- Basic movements along this plane are flexion and extension
Coronal plane- It is an imaginary vertical plane
- It is at right angles to the sagittal plane
- This plane divides the body into an anterior/ventral part and a posterior/dorsal part
- Basic movements along this plane are abduction and adduction
Transverse plane- It is at right angles to both the sagittal and frontal planes
- This plane divides the body/limb into an upper part and a lower part
- Basic movements along this plane are rotations
Oblique planeIt is a plane perpendicular to all the above planes
- Myocardium
- Myo = muscle (prefix)
- Cardio = heart (root)
- Myocardium = muscular wall of the heart
- Appendicitis
- Appendix = appendix (a specific organ) (root)
- Itis = inflammation (suffix)
Naming of Structures
Names identify structures according to:
- Shape: Trapezius muscle—trapezius= trapezoid in shape
- Size: Palmaris longus—long tendon extending to palm
- Color: Erythrocyte—erythro = red (color), cyte = cell
- Function: Adductor magnus muscle—Ad = toward mid line (direction), duct = to carry (function), magnus = very large (size). It means a very large muscle that carries the function of moving towards midline.
- Location: Quadriceps femoris muscle—Quadri = four (number), ceps = head (shape), femoris = in relation to femur (location).
Importance of Spelling
While writing medical records, misspellings can be the basis for life-threatening medical errors. Example: Difference between perineum (area between the genitals and the anus) and peritoneum (membrane covering intestines and lining the abdomen). Just two (to) letters and the whole meaning of a sentence or paragraph or medical record is changed.
Anatomically Related Terms
To describe various structures with reference to each other, several terms are required.
Descriptive Terms Indicating Direction and Location
These are described for describing along midsagittal and transverse planes. These are pair of words with meaning in opposite direction. These are used for expressing the relationship of a given structure to another structure. They are presented in Table 1.6 and Figures 1.7A to I.11
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History of Anatomy
Herophilus (335–280 BC)
- Greek physician—Father of Anatomy
- Made a twist in medicine.
- Introduced human experimentation.
- He started the practice of making incisions on human beings and doing public dissections on human corpses.
- Described the eye, liver, salivary glands, pancreas, genitals, duodenum, prostate gland, and measuring of pulse.
- First to distinguish nerves from tendons.
- He discovered parts of brain.
- Described a part of the cerebellum and called it calamus scriptorius, because it looked like a writing pen.
“When health is absent, wisdom cannot reveal itself, art cannot manifest, strength cannot fight, wealth becomes useless, and intelligence cannot be applied.”
—Herophilus
Galen of Pergamum (130–210 AD)
- Ancient Roman physician.
- Conducted dissections of monkeys, pigs.
“The best physician is also a philosopher.”
—Galen
Mondino de Liuzzi–Mundinus (1270–1326)
- Italian physician and anatomist—restorer of anatomy.
- First to incorporate a systematic study of anatomy and dissection into a medical curriculum.
- Written first dissection manual and true anatomy text.
- Stated that the purpose of anatomy is the verification or demonstration of the text.
Leonardo da Vinci (1452–1519)
- A Master of Arts, Mathematics, Engineering and Science.
- He is known for his anatomical sketches which he used to draw by dissecting human corpses though he is not a medical person and dissection was not legal.
- He was remembered for the perfect drawing of things he observed, e.g. Mona Lisa painting in Louvre Museum of Paris.
- His work is the basis for cross-sectional anatomy.
Andreas Vesalius (1514–1564)
- He is the first medical student to dissect human body who continued as professor of anatomy in Padua in Italy.
- He emphasized that anatomy can be learnt only through dissection.
- He wrote 7 volumes De (On the Fabric of the Human Body).
- His drawings were like a 3D view of anatomy.
“I am not accustomed to saying anything with certainty after only one or two observations.”
—Andreas Vesalius
William Hunter (1718–1783)
- Scottish anatomist and obstetrician.
- He started the procedure of embalming of the cadaver.
- He worked till he dropped and lectured when he was dying.
- His head was preserved in the Hunterian Museum, Glasgow, Scotland.
Henry Gray (1827–1861)
- English anatomist.
- He is recipient of Astley Cooper Prize for his work “On the Structure and Use of Spleen”.
- In 1858, his first edition of Anatomy, with 750 pages and 363 figures was published.
20th and 21st Century
- The cadaveric dissections were made compulsory in learning anatomy.
- There is increased zeal to learn anatomy. This lead to stealing of cadavers from grave yards. The scandal of Burke the butcher, Hare the thief and Knox the person who buys the cadavers was brought to light. Warburton Anatomy Act came into effect taking the legal aspects into consideration for cadaveric dissections.
- Anatomy was recognized as a science and the chemical formalin was used as a preservative to preserve the dead bodies.
- Formation of anatomical societies was encouraged.
- Anatomy acts—United Kingdom (UK) Murder Act (1752) permitted use of corpses of executed criminals for dissection. Anatomy Act of UK (1832) permitted donation of the body of the deceased by his kin for dissection purpose. Bombay Anatomy Act (1949) modified in 1975 was formulated for use of unclaimed body in an approved institution for anatomy dissection or for similar medical education uses.
- Body donation awareness: With increasing awareness of organ and body donation, several voluntary organizations are encouraging body donation to overcome the shortage of cadavers.
1. Define anatomy.
2. Describe anatomical position.
3. Define terms used to describe anatomical directions and planes of the body.
4. Name the different organ systems of human body.