DIFFERENT ORGAN SYSTEMS
● Osseous System (Skeleton) : Our modern buildings and machines appear as "Engineering Marvels". However, many of the so called ingenious devices seen in bridges, buildings and machines are also observed in the human skeleton. The primary purpose of skeleton is to support the body. It is strong enough to resist great pressure, yet flexible enough to absorb a certain amount of shock, without shattering. It also permits necessary movements.
The skeleton is the framework of bones which are organized to form distinct parts such as skull, vertebral column, thoracic cage, upper and lower extremity bones.
● Articular System : The articular system is joining various bones at their ends or edges by means of cartilages, membranes and ligaments. The joints give the movements by co-ordinated contraction of groups of muscles which are controlled by nerves.
● Muscular System : There are three types of muscles in the body.
(1) Skeletal
(2) Visceral
(3) Cardiac
Their names suggest, their location. Skeletal muscles are usually attached to bones, visceral muscles are found in the visceral organs such as stomach, intestine etc. and the heart is made up of cardiac muscles. Skeletal muscles are voluntary, while cardiac and visceral muscles are involuntary in nature. Involuntary and voluntary muscles are controlled by autonomic and central nervous system respectively. Skeletal muscles work with bones, ligaments and cartilages to produce movement at the body joints.
● Digestive System : Food is one of the basic needs of life. Digestive system is concerned with food - its swallowing, digestion, absorption, assimilation and metabolism. The digestive system consists of alimentary canal and the associated glands. The alimentary canal starts from the mouth as a hollow musculo-glandular tube, dilated and deviated, on its about 30 feet devious journey and ends at the anus. Various parts of the alimentary canal are pharynx, oesophagus, stomach, duodenum, jejunum, ileum. caecum, large intestine (colon) and the rectum. The associated glands are salivary, pancreas and liver.
The digestion takes place mainly in duodenum and jejunum. However, it starts with the digestion of starch in the mouth. Stomach stores and mechanically churns the food. Partial digestion of food specially of proteins also start here. Pancreatic secretion, bile and intestinal secretions provide enzymes for the digestion. The gastric and intestinal peristaltic movements produce mechanical digestion as against the biochemical secretion. Absorption of the digested food occurs in the small intestine. Water is mainly absorbed from stomach and the colon. Various drugs and vitamins are absorbed from the small intestine. The liver is the metabolic factory of the body and metabolism of the foods occurs here. Liver is thus the lever of health.
● Respiratory System : One can live without food for a month or so but one cannot survive for more than few minutes without oxygen. This oxygen is continuously being exchanged with carbon dioxide in the body through the respiratory system. It consists of nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles and lungs. Intercostal muscles (external and and diaphragm are the respiratory muscles which and relax for inspiration and expiration respectively.
● Cardiovascular System : The functioning of a city is possible through an intricate system of streets and roads which link houses, offices, stores, factories, hospitals and other key places. Various parts of the human body require continual supply of nutrient and oxygen and a continual removal of waste. This is being done by the circulatory system. It consists of the pumping station the heart and the intricate network of blood vessels. The blood vessels which carry blood from the heart are the arteries. They divide and redivide into arterioles, finally ending into minute hair like capillaries. The capillaries form venules and veins which bring the blood back from various parts of the body and pour it into the heart.
Blood is the vital fluid of the body which is concerned with the transport of respiratory gases, nutrition and excretory products. Besides, it is also involved in the maintenance of water, acid-base balance (pH), body temperature and hence, homeostasis of the body. Leucocytes (WBC) present in the blood give protection to the body from bacteria, toxins, foreign material etc.
● Lymphatic System : Connected to the circulatory system is the lymphatic system which consists of the closed lymphatic vessels containing a fluid called lymph. The lymph flows in lymph sinuses, capillaries and vessels ending in lymph nodes. The lymph nodes are finally drained into the heart through lymphatic ducts which end in subclavian vein.
● Excretory System : It includes mainly the kidneys, ureters, urinary bladder and urethra. It works to eliminate the waste products of cell activity through urine which is formed in the kidney, stored in the urinary bladder and is voided outside at regular intervals through the urethra.
The lungs, sweat glands of the skin and intestine also participate in the excretory functions.
● Reproductive System: The continuity of the species is maintained by reproduction. In the highest evolved organism, i.e. human being, the mode of reproduction is sexual.
Sex is the character which divides the world into two groups, male and female.
1] Male :- In male, there are two testes situated in the scrotal bag. They form spermatozoa and secrete the hormone testosterone. The vas-deferens, a cord like structure carries the spermatozoa to seminal vesicles and the prostate gland. Seminal vesicles are situated behind the bladder and open via ducts into the prostate at the mouth of the bladder. Semen is the male sex secretion and contains billions of live spermatozoa. A spermatozoa is the unit of male contribution to start a new life through zygote.
2] Female :- Female reproductive organs include vaginal canal, uterus, fallopian tubes and ovaries. Vaginal canal extends from the cervix of the uterus to outside. The uterus is the organ where the development of baby takes place. It is an inverted pear like structure with thick walls. Two uterine or fallopian tubes, one on each side opening into the uterus. In this tube, glides small mustard size, ovum which comes from the ovary once a month. There is one ovary on each side. The ovum is the unit of sex life in woman. If the male sperm unites with the ovum after coitus, a zygote is formed. This multiplies and differentiates to give a baby, which represents the genetic traits of parents and ancestors of either side.
● Nervous System : This is the system of control and co-ordination of the body. It can be compared with a complex telephone system which consists of central telephone exchange that interconnects, controls and co-ordinates a vast branching network of telephone wires, carrying a dazzling number of incoming and outgoing messages. The central telephone exchange is comparable to the central nervous system comprising of the brain and the spinal cord. The wires are like nerves passing through various junction boxes called ganglia. Physiologically, the voluntary activities are controlled by the somatic nervous system and the involuntary activities are controlled by the autonomic nervous system.
● Endocrine System : Besides the nervous system, the body activities are also controlled by chemicals called hormones. They are secreted by the specialized ductless glands-endocrine glands. These glands pour their secretions directly into the blood. Various endocrine glands are pituitary, thyroid, parathyroid, thymus, suprarenal (adrenal),testes, ovaries, placenta and the pancreas.
Although different organ systems are functionally independent, they are interdependent on each other. For example bones, joints and ligaments are all concerned with movement. The movement is not only necessary for locomotion but also for various functions like circulation, respiration and propulsion of food for digestion etc. The muscular system itself is controlled by the nervous system, the vitality of which is dependent on adequate supply of oxygen through the blood. The nervous system controls all other systems of the body and thus reigns supreme. These few illustrations show that the human physiological systems work in co-operation and co-ordination.
● Homeostasis : The human body apparently looks solid like but it holds within it, nearly 70 % of water in the form of plasma, lymph, tissue fluid and transcellular fluid. In human body, the composition of blood and body fluids generally vary with respect to gases and solids within very narrow limits. Various organs such as skin, kidneys, lungs, endocrine glands etc. interact in the most complex manner and carry out their functions with such a precision that the relative consistency is maintained among body fluids. They respond with the utmost delicacy to any condition which might tend to cause any departure from the normal state. This mechanism regulating the integrity of body fluids is termed as homeostasis. It is the keystone to longevity of life.
One of the classical example of homeostasis is the mainteance of the blood glucose level within narrow limits. Any factor which tends to increase or decrease blood sugar level will result into activation of counteracting mechanisms. This inturm leads to normalization of the blood sugar level. There are two hormones of puncreas viz. insulim and glucogon maintain the blood sugar level.
