Name 3 kinds of cells present in blood. Write one function of each of these cells.

Blood contains 55% of plasma and 45% of blood cells (formed elements). There are 3 kinds of cells in blood, namely erythrocytes (red blood cells), leucocytes (white blood cells) and thrombocytes (platelets).

RBCs are formed in the red bone marrow and are the most abundant in number (5-5.5 million per mm³). They contain haemoglobin that binds to respiratory gases but lacks a nucleus.

WBCs are of 2 categories – granulocytes and agranulocytes. They are relatively lesser in number (6000-8000 per mm³). They lack haemoglobin but are nucleated.

Platelets are formed in the bone marrow from megakaryocytes. Blood usually contains 1.5-3.5 lakh platelets per mm³. The decrease in their number can cause blood clotting disorders.