________________
Perception of Body
sition remains surprisingly constant. The main components of the blood are :
1. Blood-plasma-A clear straw-coloured fluid in which are dissolved salts, proteins, fats, sugár, hormoncs, vitamins, as well as waste products such as urea and lactic
acid.
2. Red Blood Cells--These are small flattened biconcave discs. 3000 of them would be needed to measure an inch. There are five million red cells per cubic millimetre. Every second, three million cells die and equal number of them are born.
Haemoglobin-The red pigment of the red cells is an iron containing protein. Total amount of iron in the haemoglobin of all the red cells is about 3 grammes. But it is priceless as one cannot live without it.
3. White Blood Cells—They are larger and fewer than red cells. They are colourless and not uniform in size, shape and appearance. They are the soldiers of the : body--defenders against foreign invaders--ready to fight to death.
4. Platelets-They go into action when a blood vessel is cut or pierced and blood is being lost. A substance called platelet factor initiates a chain of chemical reactions leading to the formation of a clot which effectively plugs the cut or hole.
3. Respiratory System The body needs a continual supply of oxygen. In addition, the body also needs some means of disposing of the waste carbon dioxide, produced by the body cells. Respiratory system fulfils both these requirements.
This system includes passage-ways and tubes through which the air passes : the nose, trachea, bronchi and bronchioles arranged in a sequence that branches and rebranches and looks like an inverted tree. The tubes end in tiny air sacs called alveoli in which the exchange of gases takes place. The bronchioles and alveoli constitute the lungs. Human lungs contain about 300 to 500 millions
Jain Education International
For Private & Personal Use Only
www.jainelibrary.org
