Cardio Syst - Blood
Terms in this set (10)
Three Basic Stages of Blood Clotting
1) Formation of prothrombinase (prothrombin activator). Initiated by either the extrinsic or the intrinsic pathway or both.
(2) Conversion of prothrombin (a plasma protein formed by the liver) into the enzyme thrombin by prothrombinase.
(3) Conversion of soluble fibrinogen (another plasma protein formed in the liver) into soluble fibrin by thrombin.
- Fibrin forms the threads of the clot.
Formation of Prothrombinase
- Two mechanisms are involved: (a) extrinsic, and (b) intrinsic pathways
- Outside blood vessels, rapid
- Tissue Factor (TF) leaks into the blood from cells outside (extrinsic to) blood vessels and initiates the formation of prothroombinase
- Activates clotting factor VII, which activates factor X.Activated factor X combines with factor V in the presence of calcium ions (Ca2+) to form the active enzym prothrombinase
- Within the blood vessel, slower
- Activators are in direct contact with blood or contained within (intrinsic to) the blood; outside tissue damage is not needed
- damaged epithelium causes collagen to contact Factor XII and acivates -> cascade -> activate Factor X -> Factor X+Factor V+Ca2+ => Prothrombinase
- Stages 2 &3
- In the second stage, prothrombinase and Ca2+ catalyze the conversion of prothrombin to thrombin.
- In the third stage, thrombin, in the presence of Ca2+, converts fibrinogen, which is soluble, to loose fibrin threads, which are insoluble.
- Normal clotting depends on adequate vitamin K in the body
- Although vitamin K is not involved in actual clot formation, it is required for the synthesis of four clotting factors by liver cells:(Factors II (prothrombin), VII, IX, and X).
- Vitamin K is normally produced by bacteria in the large intestine
- Clotting in an unbroken blood vessel (usually a vein)
- Clot itself
- A blood clot, bubble of air, fat from broken bones, or a piece of debris transported by the bloodstream
- Condition that results when embolus lodges in the lungs.
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