Respiratory System
Breathing — involves intake of oxygen (inspiration) from atmospheric air and expulsion of carbon dioxide (expiration). The respiratory system is composed of nostrils, wind pipe or trachea, bronchi and bronchioles, lungs. The lungs are enclosed in a compartment formed by the ribs, the breast bone and backbone and perform the function of respiration.
Endocrine System
Endocrine — is the system of ductless glands linked by nervous and circulatory system. They secrete hormones. The hormones control growth and other essential activities in the life process of the body.
Pituitary — is a small gland situated beneath the brain. It secretes the important pituitrin hormone. Its over-secretion in childhood produces "giants" and in adult life "acromegaly" where growth of the parts of the body is disproportionately increased as gorilla like appearance.
Excretory System
Excretory system — It eliminates harmful waste products formed in the body. The main excretory organs are lungs, kidneys, skin and large intestine. Lungs throw out carbon dioxide and water vapour. Large intestine excretes waste matter of digestion as faeces and kidneys excrete urine. Skin excretes sweat. Kidneys take away the nitrogenous end products of the metabolism, chiefly urea. The blood entering kidneys brings urea, uric acid, large quantities of water, sugar and various salts which, by filtration, are eliminated with urine. Kidneys also absorb certain useful constituents such as glucose, water and salts. Skin protects the body, regulates the temperature of die body, excretes waste matter, gives the sense of touch and stores reserve food.
Nervous System
Nervous system controls and regulates the activities of all the other systems of body. It coordinates the reception of external stimuli and responds to them by sensory nerves and motor nerves. The whole system is divided into three parts — (1) the central nervous system, (2) the peripheral nervous system, and (3) the autonomic nervous system.
Central nervous system consists of brain and spinal cord safely lodged in the brain case and vertebral column. The brain controls voluntary actions, intelligence, memory, association, imagination and will. Cerebellum regulates the muscular movement of the body coordinating them. Medulla-oblongata controls involuntary actions of breathing and heartbeat. The spinal cord is an elongated cylindrical continuation of medulla and regulates various reflex actions.
Peripheral nervous system consists of nerves which arise from the brain and the spinal cord.
Autonomic nervous system controls the internal activities of visceral organs, i.e., the circulation, digestion over which we have no voluntary control.
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