Blood must flow freely and not clot unless there is a break in a blood vessel. Clotting is normally triggered by a rough edge in a blood vessel, such as a cut artery. The liver synthesizes several proteins important in blood clotting including prothrombin and fibrinogen. These two proteins circulate in blood.
One of the first steps in blood clotting is triggered by the formation of thrombin from prothrombin, as seen in Figure 6-1. Thrombin then accelerates the conversion of fibrinogen to fibrin, which consists of fine threads that tangle together to form a blood clot. Vitamin K is necessary in order for the liver to synthesize rothrombin. Vitamin K converts the glutamic acid that is in prothrombin, enabling it to bind to calcium.
Without adequate vitamin K, prothrombin production slows, leading to a bleeding tendency. There are several other proteins involved in blood clotting that are activated by vitamin K. Balance and control are important parts of blood clotting. In addition to speeding blood clotting, vitamin K also assists in creating proteins that slow blood clotting. Vitamin K is needed to synthesize two proteins, protein C and protein S,
Figure 6-1 The role of vitamin K in blood clotting.
which are important inhibitors of coagulation. Protein S is also synthesized by the blood vessel walls where it has a role as a coagulation inhibitor .
One of the first steps in blood clotting is triggered by the formation of thrombin from prothrombin, as seen in Figure 6-1. Thrombin then accelerates the conversion of fibrinogen to fibrin, which consists of fine threads that tangle together to form a blood clot. Vitamin K is necessary in order for the liver to synthesize rothrombin. Vitamin K converts the glutamic acid that is in prothrombin, enabling it to bind to calcium.
Without adequate vitamin K, prothrombin production slows, leading to a bleeding tendency. There are several other proteins involved in blood clotting that are activated by vitamin K. Balance and control are important parts of blood clotting. In addition to speeding blood clotting, vitamin K also assists in creating proteins that slow blood clotting. Vitamin K is needed to synthesize two proteins, protein C and protein S,
which are important inhibitors of coagulation. Protein S is also synthesized by the blood vessel walls where it has a role as a coagulation inhibitor .
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