Blood Clotting

• Why does your blood clot ?
• How does blood clotting occur ?
• Why does blood clot within the bloodstream ?
• What happens to the foreign invasive particles that might have entered the bloodstream ?
• How does the body dissolve the clot to heal the wound ?

Why does your blood clot?
When you get a cut or bruise, your blood exposed to the air will clot. The clot seals the wound to prevent excessive blood loss while at the same time preventing foreign invasive particles from entering your bloodstream. Clotting is the solidification of blood in a process known as coagulation. A blood clot consists of a plug of platelets enmeshed in a network of insoluble fibrin.

How does clotting occur?
When blood vessels are severed/damaged, the enzyme thrombokinase is secreted by the damaged tissues and blood platelets in the bloodstream. Thrombokinase converts the prothrombin which a soluble protein in the bloodstream into thrombin. Calcium ions must be present before this can take place. Thrombin is an enzyme that catalyses soluble fibrinogen into a network of insoluble fibrin over the wound. Other essential elements that include the presence of vital minerals and vitamins (i.e. vitamin K)

Why does blood clot within the bloodstream?
Blood possesses an anti-coagulation substance called heparin, which is produced by the liver. When thrombokinase is released, it neutralises the action of heparin so that clotting can effectively take place.

What happens to the foreign invasive particles that might have entered the bloodstream?
Foreign invasive particles such as bacteria that might have entered the bloodstream are subjected to attacks from the white blood cells in the bloodstream. Antibodies will be secreted to cause them to agglutinate before finally before being eliminated via phagocytosis, where the foreign particles are engulfed and ingested by the white blood cells.

How does the body dissolve the clot to heal the wound?
Plasma contains plasminogen that binds the fibrin molecules in the clot. When the wound has healed, the normal cells would secrete tissue plasminogen activator (TPA) to attach themselves to the clot, converting the plasminogen to plasmin. Plasmin will digest the fibrin and dissolve the clot when the wound has covered up and healed.