THE HUMAN BODY : AN ORIENTATION
This chapter is devoted to the study of internal morphology, body wall and coelom of man. Knowledge of
some of these topics may prove useful to the study of human anatomy and physiology.
(Ana – up, Tome – Cutting) Study of internal structure of body with naked eye after dissection.
(A) Gross Anatomy : Study of large internal structures e.g. Heart, liver, Kidney.
(B) Microanatomy : Study of smaller internal structures with the help of microscope. It is divided into
(a) Histology – Study of tissues.
(b) Cytology – Study of structure of cell.
(C) Developmental Anatomy : Study of structural changes in an individual from conception to old age.
(D) Pathological Anatomy : Study of structural changes in cells, tissues and organs due to disease.
(E) Radiography Anatomy : Study of anatomy by means of radiographic images.
(Physics – Functioning, logos – study)
Study of various body functions. e.g. Digestion, respiration, excretion etc.
It has following branches :
(A) Physical Physiology: Study of physical activities which take place in the body e.g. pumping of
heart, contraction of muscles.
(B) Chemical physiology: Study of chemical changes which take place in the body e.g. hydrolytic
breakdown of food, Breakdown of glucose in respiration, protein synthesis etc.
Note : Both Anatomy and physiology are Complementary to each other because without structure
functioning can not take place.
Hierarchy of structural organization in humans :
Organisation is a systematic arrangement of smaller and simpler components in to larger and more
complex ones in a hierarchy of levels, where each higher level is formed of components of lower
level and itself becomes a part of still higher level for achieving a common goal.
Following types of organization found in humans :
(A) Atomic level : It is a basic unit of organization in human beings. An atom is made up of smaller or
subatomic particles like electrons, protons and neutrons e.g. Atoms of C, H, O, N.
(B) Molecular level : Atoms become associated to form molecules. The molecules found in living
system are known as biomolecules.
e.g. – Molecules of protein, lipid, starch etc.
(C) Sub cellular level – Different biomolecules combine to form cell organelles e.g. cell membrane,
(D) Cellular level : Cell organelles associate to each other and form cell which is the structural and
functional unit of human body. e.g. muscle cell, nerve cell etc.
(E) Tissue level : Cells are organised into tissue each of which has a common origin and function.
e.g. Epithelial, connective, muscular and nervous tissue.
(F) Organ level : Tissues are aggregated to form organs, each with a specific function.
e.g. Kidney, Heart etc.
(G) Organ System level : Organs coordinate their functioning to form an organ system e.g. Digestive,
respiratory and excretory system.
(H) Organismic or Individual level : A distinct entity or individual is formed by the integration of
Maintenance of life
The human beings share certain unified and basic characteristics like maintenance of boundaries by
integumentary system due to which internal environment remains distinct from the external environment It
also protects internal organs from drying out and being invaded by foreign agents. Some functional
characteristics are as follows :
(i) Cellular Structure. Each living being is a complex entity which is formed of one or more cells.
(ii) Organisation. It has an organization, that is, the living being consists of several components which
cooperate with one another for the well being of the whole organism.
(iii) Energy. It constantly receives energy not only to perform various activities of the body but also to
overcome entropy or tendency to randomness.
(iv) Homeostasis . It shows homeostasis or ability to maintain perfect internal environment through self
(v) Response. It is able to recognise and respond to different types of external and internal stimuli.
(vi) Growth. A living being is able to grow in size and attain maturity.
(vii) Reproduction. Life comes from pre-existing life. Young-ones grow and become mature. They
develop the faculty to produce young-ones of their own type.
(viii) Assimilation. It is able to obtain raw materials from outside and convert them into protoplasmic
(ix) Metabolism. A living being carries out numerous chemical processes in an organized and controlled
fashion. They constitute metabolism. Metabolism has two types of reactions, catabolism (break-up
reactions. e.g. cellular respiration) and anabolism (build-up reaction e.g. formation of glycogen by
(x) Healing and Repair. Living beings are