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Composition of the blood:

Blood consists of a faintly yellow fluid, the plasma or liquor sanguinis, in which are suspended numerous minute particles, the blood corpuscles, the majority of which are coloured and give the blood its red tint.

Functions of Blood

(i) Carries oxygen and essential nourishment through arteries to every living tissue in the body.

(ii) Carbon dioxide and waste products generated in the body by metabolism (Metabolism are all chemical processes which govern living organisms), such as urea, are removed by the blood through veins. (iii) Controls body temperature. (iv) Defends against infections.

Constituents of Blood: There are two main constituents of blood, viz., the solid or cellular part called blood cells (35 per cent) and fluid or humoral part called plasma (65 per cent). Blood cells, called corpuscles, are of three types. (i) Red Blood Corpuscles (RBC) RBCs, which are called erythrocytes, are disc-shaped cells. They have no nucleus and contain a pigment called haemoglobin which gives blood its red colour. RBCs are produced in the spleen. The life of an RBC is about 100-120 days.

(ii) White Blood Corpuscles (WBC) WBCs are the ‘soldiers’ of the body’s defence system. They are a little larger than RBCs.

Blood grouping K. Landsteiner, in 1900-02, classified human blood into four groups, A, B, AB, and O. The cells of these groups contain the corresponding antigens—A, B, AB, except O cells which contain neither antigen A nor B.

Blood Pressure :It is the force exerted by the blood beating against artery walls. The highest point in the pressure range is called systolic pressure (upper reading) and lowest point in the pressure is called diastolic pressure (lower reading). 120/80 is the normal blood pressure.



Vertebral column    26

Skull                        22

Hyoid bone               1

Ribs and sternum   25


Upper extremities    64

Lower extremities    62


Auditory ossicles       6

Total                      206


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