Question

Describe the structure and functions of thrombocytes

Answer 1

Thrombocytes are also known as platelets.

• Platelets are small irregularly shaped cells formed from large bone marrow cells called megakaryocytes.
• There are about 250,000 platelets per cubic millimetre of blood.
• They initiate the process of blood clotting.
• The process of clotting involves a series of complex reactions whereby fibrinogen is converted into a fibrin clot.
• When blood vessels are injured platelets are exposed to air and they release thromboplastin (thrombokinase) which initiates the blood clotting process.
• Thromboplastin neutralises heparin the anti-clotting factor in blood and activates prothrombin to thrombin.
• The process requires calcium ions and vitamin K.
• Thrombin activates the conversion of fibrinogen to fibrin which forms a meshwork of fibres on the cut surface to trap red blood cells to form a clot.
• The clot forms a scab that stops bleeding and protects the damaged tissues from entry of micro-organisms.
• Blood clotting reduces loss of blood when blood vessels are injured.
• Excessive loss of blood leads to anaemia and dehydration.
• Mineral salts lost in blood leads to osmotic imbalance in the body.
• This can be corrected through blood transfusion and intravenous fluid.