The following points highlight the top six ways by which RBC’s are destroyed by hemolysis. The ways are: 1. Osmotically 2. By hemotoxins 3. By Certain Drugs 4. By Lipid Solvents 5. By Mechanical Means 6. Other Hemolytic Agents.
Way # 1. Osmotically:
(i) The RBC membrane is permeable to water. When the blood is placed in hypotonic solution, red cells swell owing to water passing in. If the solution is more hypotonic, the red cells swell up more and hemoglobin comes out of the red cell due to the rupture of its membrane.
(ii) If the cells are placed in a hypertonic solution, water passes out of the cells and the cells shrink due to reduction in volume. The process is called crenation.
Way # 2. By hemotoxins:
(i) Snake venom and certain other bacteria can produce hemolysis in vivo. The hemolytic effect is due to the presence of the enzyme phospholipase A which hydrolyses phospholipids and thus disrupts the cell membrane.
(ii) The W.R. (Wassermann reaction) for syphilis employs a hemolytic system, produced by the injection of foreign red cells into an animal such as a rabbit.
Way # 3. By Certain Drugs:
Quinine, nitrites and chlorates cause hemolysis.
Way # 4. By Lipid Solvents:
Alcohol, chloroform, ether, bile salts and saponin cause hemolysis due to their solvent action on the lipid of the plasma membrane.
Way # 5. By Mechanical Means:
Grinding, vigorous stirring or shaking causes destruction of erythrocytes.
Way # 6. Other Hemolytic Agents:
Heat, pH changes, ultraviolet light, etc. can cause hemolysis.
Stop of bleeding is said to be hemostasis.
There are four phases of hemostasis:
(i) The first phase is the constriction of the injured vessel to reduce blood flow.
(ii) The second phase consists of formation of a loose platelet plug or white thrombus at the site of injury. Collagen is exposed at the site of injury and acts as a binding site for platelets.
(iii) The third phase is the formation of red thrombus (blood clot).
(iv) The fourth phase is the partial or complete dissolution of the clot.
Clots are of three types:
The white thrombus is composed of platelets and fibrin and is poor in erythrocytes. It is formed at the site of injury, particularly in areas of rapid blood flow (arteries). The second type of thrombus is deposited in small vessels (capillaries). The third type is the red thrombus and consists of red cells and fibrin.
Initiation of clot formation to tissue injury is carried out by extrinsic pathway and the initiation of the pure red thrombus in an area of restricted blood flow without tissue injury is carried out by intrinsic pathway. The intrinsic and the extrinsic pathway merge into a final common pathway-the activation of prothrombin to thrombin and thrombin catalysed fibrinogen to fibrin clot.
The blood clotting factors are mentioned below:
