- a special connective tissue consisting of a fluid matrix, plasma, and formed elements. 
Plasma
- a straw coloured, viscous fluid constituting nearly 55 % of the blood. 90-92 % of plasma is water and proteins contribute 6-8 % of it.
Composition: Fibrinogen, globulin and albumin are the major proteins.
² Fibrinogen - clotting or coagulation of blood (In inactive form). Plasma without the clotting factors is called serum.
² Globulin - defense mechanisms of the body.
² Albumin - Osmotic Balance.
- also contains small amounts of minerals like Na+ , Ca++, Mg++, HCO3 – , Cl– , etc. Glucose, amino acids, lipids, etc., are in transit in the body.
Formed Elements
- Erythrocytes, leucocyte and platelets are collectively called formed elements constitute nearly 45 % of the blood.
Erythrocytes | Leucocytes | Thrombocytes |
Also called as red blood cells (RBC) | Also called as white blood cells (WBC) | Also called as platelets. |
Most abundant of all the cells in blood, on an average of 5 millions to 5.5 millions of RBC mm–3 of blood. | Relatively lesser in number which averages 6000-8000 mm–3 of blood | contains 1,500,00-3,500,00 platelets mm–3. |
Are biconcave in shape and have a red coloured, iron containing complex protein called haemoglobin constitute 12-16 gms in every 100 ml of blood. | Colourless due to the lack of haemoglobin. | are small, colorless cell fragments in our blood |
Formed in the red bone marrow in the adults and are devoid of nucleus in most of the mammals (young RBC has but mature lacks). | are made in the bone marrow. | are cell fragments produced from megakaryocytes (special cells in the bone marrow). |
Average life span of 120 days after which they are destroyed in the spleen (graveyard of RBCs). | are generally short lived ie., 13 to 20 days, after which time they are destroyed in the lymphatic system. | The lifespan of thrombocyte is five to 10 days.Under conditions of TCP, the spleen and liver are the sites for accelerated platelet destruction. |
- | Two main categories of WBCs – granulocytes and agranulocytes.
Neutrophils (are the most abundant cells (60-65%) of the total WBCs & neutrophils and monocytes are phagocytic cells which destroy foreign organisms entering the body), Eosinophils (present as (2-3%) resist infections and are also associated with allergic reactions.) and basophils (are the least (0.5 - 1%) & secrete histamine, serotonin, heparin, etc., and are involved in inflammatory reactions.) are different types of granulocytes.
Lymphocytes ( as (20-25 %) are of two major types – ‘B’ and ‘T’ forms. Both B and T lymphocytes are responsible for immune responses of the body) and Monocyte (present as (6-8%) neutrophils and monocytes are phagocytic cells which destroy foreign organisms entering the body) are the agranulocytes. | Platelets can release a variety of substances most of which are involved in the coagulation/clotting of blood. A reduction in their number can lead to clotting disorders. |
