Clotting factors Health Dictionary

See COAGULATION.... clotting time

The process of blood solidification. Clotting is important in stemming bleeding from damaged blood vessels. However, unwanted blood clotting can occur inside major blood vessels and cause a myocardial infarction (heart attack) or stroke (see thrombosis).

When a blood vessel is damaged, it constricts immediately to reduce blood flow to the area. The damage sets off a series of chemical reactions that lead to the formation of a clot to seal the injury. First, platelets around the injury site are activated, becoming sticky and adhering to the blood-vessel wall. Then, the activated platelets release chemicals, which, in turn, activate blood clotting factors. These factors, together with vitamin K, act on fibrinogen and convert it to fibrin. Strands of fibrin form a meshwork, which traps red blood cells to form a clot.

There are several anticlotting mechanisms to prevent the formation of unwanted clots. These include prostacyclin (a prostaglandin), which prevents platelet aggregation, and plasmin, which breaks down fibrin (see fibrinolysis). Blood flow washes away active coagulation factors; and the liver deactivates excess coagulation factors.

Defects in blood clotting may result in bleeding disorders.

Excessive clotting (thrombosis) may be due to an inherited increase or defect in a coagulation factor (see factor V), the use of oral contraceptives, a decrease in the level of enzymes that inhibit coagulation, or sluggish blood flow through a particular area.

Treatment is usually with anticoagulant drugs such as heparin or warfarin.... blood clotting

Various compounds and processes that enable the liver to metabolize fats properly or prevent the formation of cholesterolic stones in the gall bladder by supporting the continued emulsification of gall bladder bile. EXAMPLES: Lecithin, choline, Aristolochia... lipotropic factors

Tests to screen for and diagnose bleeding disorders, usually resulting from deficiencies or abnormalities of blood coagulation factors or of platelets (see blood clotting). Tests are also used to monitor treatment with anticoagulant drugs.... blood-clotting tests

Factors that lead to increased susceptibility to a disease.... predisposing factors

A group of hormones, produced by the hypothalamus in the brain, that stimulates the release of other hormones.

Luteinizing hormone-releasing hormone is one such releasing factor.... releasing factors

a group of *growth factors that promote new bone formation. Bone morphogenic protein (BMP), a naturally occurring substance that induces *osteoblast formation, has been genetically synthesized to form bone morphogenetic protein, which stimulates new bone formation and assists with fracture healing. Other bone growth factors include a type of transforming growth factor (TGF?) and insulin-like growth factor II (IGF-II), which encourage collagen formation.... bone growth factors

(clotting factors) a group of substances present in blood plasma that, under certain circumstances, undergo a series of chemical reactions leading to the conversion of blood from a liquid to a solid state (see blood coagulation). Although they have specific names, most coagulation factors are referred to by an agreed set of Roman numerals (e.g. *Factor VIII, *Factor IX). Lack of any of these factors in the blood results in the inability of the blood to clot. See also haemophilia.... coagulation factors