Blood Clotting & How It Occurs

Blood clotting, or blood coagulation, can best be described as the blood's ability to lump up, and literally change from its fluid form. Usually, blood within the capillaries remains in its fluid form, but it may clot due to tissue injury or severe contact with rough surfaces. A sealant called fibrinogen is always present in an inactive form. The enzyme - thrombin -- can cut the fibrinogen into smaller sections called fibrin. It is fibrin which combines into a mesh of threads that form the "fabric" of the clot itself. The process of clotting begins with the release of many factors including substances from the platelets and calcium salts. With these components and a complex series of reactions, the fibrinogen is transformed into fibrin and the clotting takes place. If a person has too little of any of the components used in clotting, this can lead to hemophilia, a condition where there is excessive bleeding from only minor cuts and bruises. Hemophilia can also be caused by the lack of vitamin K, which is crucial to the maintenance of the proper amount of the ingredients in blood clotting.

Blood Clotting

1. A vessel/tissue is damaged (fluids are leaking out)
2. Platelets (fragments of cells) in plasma attach to collagen fibers forming a plug.
3. Platelets release vasoconstrictors that cause vessels to get narrower, reducing bleeding.
4. Platelets release the enzyme thrombloplastin, which with calcium ions activated the production of thrombin in plasma.
5. Thrombin breaks large fibrinogen molecules into fibrin (sticky, fibrous, protein).
6. Fibrin fibers, damaged platelets, red cells, and white cells form networks of webbing that becomes a clot and stops the bleeding.

---