Human body is complex like a highly technical machine. It operates as a single unit but it is made up of a number of operational parts, which work interdependently. Each part is associated with a specific and sometime related functions. Human body is therefore complex in structure and function. In this book we simplify the study of structure and function.
The word Anatomy is originated from Greek word, that means “taking apart by cutting”. In anatomy we study the structure and their relation in the human body.
The term Physiology also originated from Greek word Physio—logikos meaning Discourse or Natural Knowledge. Physiology deals with the normal function of human body.
Several subdivisions of anatomy and physiology are present. Some are given below:
SUBDIVISION OF ANATOMY
- Surface anatomy—Study of form (morphology) and marking of surface of body.
- Gross anatomy—Study of structure without using microscope.
- Systemic anatomy—Study of specific system of body e.g. cardiovascular system.
- Regional anatomy—Study of specific region of body.
- Histology—Study of structure of tissue
- Cytology—Study of structure of cell
SUBDIVISION OF PHYSIOLOGY
- Cell physiology—Study of function of cells.
- Systems physiology—Study of function of system.
- Exercise physiology—Study of changes in cell and organ function during muscular activity.
- Neurophysiology—Study of function and character of nerve cells.
LEVEL OF STRUCTURAL ORGANIZATION
Our body consists of several levels of structural organisation. The lowest level of organisation is chemical level in which all atoms and molecules are included. For example protein, fat and vitamin
Molecules combine to form a structure that is called cell. Cell is the structural and functional unit of human body. Many kinds of cell are found in body. For example, nerve cell, blood cells, etc.
Several cells combine to form a structure called tissue. Tissues are group of similar cells which have common origin and same function. For example, nervous tissue, muscular tissue, etc.
Different kinds of tissue are joined to form organs, that have specific function and usually have recognisable shape, e.g. heart, liver, stomach etc.
Several organs and associated organ related to each other and having a common function form a system. For example digestive system, endocrine system, etc.
These systems have their individual organ and function and comprise total organism or human body.
Atoms→Molecules→Cell (functional and structural unit)→Tissue (similar cell group)→Organs (group of tissue)→System→Human body.
In our body 9 systems are present. They are:
- Skeletomuscular system
- Cardiovascular system (CVS)
- Digestive system
- Excretory system
- Respiratory system
- Endocrine system
- Reproductive system
- Nervous system
- Miscellaneous system (the sense organs—skin)
Skeletomuscular system: In this system we study all bones of body, cartilage and joints of body, their muscular tissue which is mainly skeletal muscle. Function—support, protection, movement and maintains posture, etc.
Cardiovascular system: In this system we study blood, heart, blood vessels, lymph, etc. Function—distribute O2 and nutrients to cell.
Digestive system: In this system we study gastrointestinal tract, associated organs such as liver, pancreas, etc. Function—physical and chemical breakdown and absorption of food.
Excretory system: In this system we study kidney, ureters, urinary bladder, urethra, etc. Function—regulate volume and chemical composition of blood, eliminate wastes and regulate electrolyte balance, etc.
Respiratory system: In this system we study lungs, respiratory tracts etc. Function—supply O2 and eliminate CO2, etc.
Endocrine system: In this system we study all hormone producing glands and cell such as the pituitary gland, thyroid gland, etc. Function—regulates body activities through hormones.
Reproductive system: In this system we study reproductive organs (testis and ovaries). Function—Reproduction.
Nervous system: In this system we study nervous organs such as brain, spinal cord, nerves. Functions—regulate all body activities.
Miscellaneous system: In this system we study special sense organs such as skin, eye, nose, etc. and skin derivatives e.g. Nail. Function—They receive sense that goes to brain and vice versa.
ANATOMICAL POSITION
For the descriptions of any region or part of human body assume that body is in a specific position i.e. called Anatomical position. In anatomical position person stands erect (upright position) facing the observer, with feet flat and close together on floor, arms placed, at the sides and palms of hands facing forward.4
Directional terms
These terms are used for the location of various body structure in relation to one another as given below:
- Anterior or ventral: Nearer or front of body, e.g. sternum anterior to heart.
- Posterior or dorsal: At back of body, e.g. oesophagus is posterior to trachea.
- Superior: Toward head or upper part of structure, e.g. Heart is superior to liver.
- Inferior: Away from head or towards lower part of structure.
- Medial: Nearer to mid line of body. (Midline is an imaginary vertical line which divides body into equal left and right side e.g. The ulna is medial side in forearm.
- Lateral: Farther from mid line of body. For example lung is lateral to heart.
- Intermediate: Between two structure.
- Proximal: Nearer to attachment of an extremity (limb) to trunk or structure, e.g. humerus is proximal to radius.
- Distal: Away to attachment of an extremity (limb) to trunk.
- Superficial: On the surface of body.
- Deep: Away from surface of body, e.g. ribs are deep to skin of chest.
- Parietal: Forming outer wall of body cavity.
- Visceral: Forming inner wall of body cavity.
Abdominopelvic region
For the location of organ it is divided into nine regions.
Right | Middle | Left |
|---|---|---|
Hypochondriac region | Epigastric region | Left hypochondriac region |
Right lumbar region | Umbilical region | Left lumbar region |
Right iliac region | Hypogastric region | Left iliac region |
Body cavities
In body many internal organs are found in cavity, i.e. called body cavity.
The cavities help to protect, separate and support the organs. Body cavities may be separated from each other by structure such as muscles, bone, ligaments.5
In body two principal body cavities are found. They are:
- Dorsal body cavity
- Ventral body cavity
Dorsal body cavity: It is located near the dorsal (back) surface of body. It subdivided into two cranial cavity, which is formed by cranial (skull) bone and contain brain and spinal or vertebral cavity or vertebral canal, which is formed by vertebrae of backbone and contain spinal cord.
Ventral body cavity: It is located on ventral (front) aspect of body. It is lined by serous membrane. The organs inside are called viscera. They are subdivided into two—upper portion called thoracic cavity and lower portion called abdomino pelvic cavity. They are further subdivided given below:
Mediastinum
It is a region between lungs, extending from sternum to vertebral column. They include all contents except lungs such as trachea, oesophagus, thymus, etc.
Homeostasis
Human body is composed of various systems and organs, each consists of millions of cell. These cells need relatively stable conditions to function effectively and contribute to survival of body as a whole. The maintenance of stable condition for its cell is an essential function, such relative stability is called Homeostasis. It is a condition in which body's internal environment remains within certain physiological limits. Homeostasis is regulated by nervous system and endocrine system.
Feedback Systems
It is a cycle of events in which information about status of a condition is continually monitored and feeded back (reported) to central control region. It consists of three basic components—control center, receptor and effector.
- Control center: Determines point at which some aspect of body is in controlled condition.
- Receptor: Monitors changes in the controlled condition and then sends information.
- Effector: Receives the information.
It is of two types
- Negative Feedback Mechanism: It is the response reverse to the original stimulus and is called Negative Feedback Mechanism. For e.g. body temperature, blood pressure (BP).Nervous system and endocrine system are regulatedr by this:
- Positive Feedback Mechanism: If the response enhances the original stimulus, i.e. called Positive Feedback Mechanism. For e.g, blood clotting, labour contraction, etc.
Body Fluid
The term body fluid refers to body water and its dissolved substances. In body near about 60 per cent total body weight fluid are present.
Those fluid present within the cell, i.e. called intra cellular fluid (ICF). It is near about 2/3 of all body fluid and the other fluid present outer side of cell, i.e. called extra cellular fluid (ECF). It is present near about 1/3 of total body fluid. In ECF, near about 80 per cent interstitial fluid and 20 per cent blood plasma are present. Some interstitial fluid is localised in specific places such as lymph in lymphatic vessels, cerebrospinal fluid in brain, synovial fluid in joint, etc.
In infants body fluid or body water is near about 75 per cent of body weight. The percentage decrease with age.
Amount of body fluid × 1/Age
Fat is basically water free. Lean people have greater proportion of water to total body weight than fat people. Male have more body fluid than female.
In body fluids many electrolytes and nonelectrolytes are present. In nonelectrolytes glucose, urea are present. They are dissolved in fluid. In electrolytic, their percentage are given below.8
ECE (meq/Lit) | ICF (meq/Lit) |
|---|---|
Cations | |
Na+136–142 | 10–15 |
K+3.6–5 | 150–155 |
Ca2+4.6–5.5 | – |
Mg2+ 2–3 | 10–16 |
Others 1–2 | 1–2 |
Anions | |
CI− 95–105 | 5–8 |
HCO−3 20–26 | 6–8 |
Phosphate (PO4)2− | 85–95 |
Other | 10–20 |