Question

Describe in detail the composition of human blood.

Answer 1

Blood is a fluid that moves through the vessels of a circulatory system. In humans, it includes plasma (the liquid portion), blood cells (which come in both red and white varieties), and cell fragments called platelets.

(i) Red blood cells or erythrocytes are the most abundant cells in blood. In healthy humans they are biconcave in shape and lack a nucleus. Haemoglobin pigment is present in RBC which binds to oxygen and transports it.

(ii) White blood cells are also called leucocytes. They are amoeboid and can squeeze through blood vessels. This is called diapedesis.

Leucocytes are classifies into granulocytes and agranulocytes. Granulocytes are neutrophils, basophils and eosinophils. Agranulocytes are monocytes (they are phagocytic in nature) and lymphocytes (responsible for immune responses).

(iii) Platelets are also called thrombocytes.They are the smallest of formed elements and are cell fragments rather than true cells. They lack nuclei and play and important role in clotting.