coagulation

Examples of coagulation in the following topics:

• Role of Vitamin K

  • Coagulation is a complex cascade that requires many different cofactors and molecules to occur.
  • Vitamin K is a fat-soluble vitamin necessary for synthesis of coagulation factors involved in the coagulation cascade.
  • Warfarin is used in medicine for those at high risk of thromboembolism to prevent the coagulation cascade by reducing vitamin K dependent synthesis of coagulation factors.
  • Calcium deficiencies inhibit proper blood coagulation.
  • Blood coagulation pathways in vivo showing the central role played by thrombin.

• Coagulation

  • Coagulation is the process by which a blood clot forms to reduce blood loss after damage to a blood vessel.
  • The coagulation factors circulate as inactive enzyme precursors, which, upon activation, take part in the series of reactions that make up the coagulation cascade.
  • The coagulation factors are generally serine proteases (enzymes).
  • Coagulation can occur even without injury, as blood pooling from prolonged immobility can cause clotting factors to accumulate and activate a coagulation cascade independently.
  • Many anticoagulants prevent unnecessary coagulation, and those that genetically lack the ability to produce these molecules will be more susceptible to coagulation.

• Platelet Plug Formation

  • The released chemicals include ADP, VWF, thromboxane A2, platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), serotonin, and coagulation factors.
  • The coagulation factors include factor V and VIII, which are involved in the coagulation cascade that converts fibrinogen into fibrin mesh after platelet plug formation.
  • The completed plug will cover the damaged components of the endothelium and will stop blood from flowing out of it, but if the wound is large enough, blood will not coagulate until the fibrin mesh from the coagulation cascade is produced, which strengthens the platelet plug.
  • If the wound is minor, the platelet plug may be enough to stop the bleeding without the coagulation cascade.

• Platelets

  • Platelets circulate in blood plasma and are primarily involved in hemostasis (stopping the flow of blood during injury), by causing the formation of blood clots, also known as coagulation.
  • Platelets secrete many factors involved in coagulation and wound healing.
  • During coagulation, they release factors that increase local platelet aggregation (thromboxane A), mediate inflammation (serotonin), and promote blood coagulation through increasing thrombin and fibrin (thromboplastin).

• Overview of Hemostasis

  • Hemostasis includes three steps that occur in a rapid sequence: (1) vascular spasm, or vasoconstriction, a brief and intense contraction of blood vessels; (2) formation of a platelet plug; and (3) blood clotting or coagulation, which reinforces the platelet plug with fibrin mesh that acts as a glue to hold the clot together.
  • The endothelial cells of intact vessels prevent clotting by expressing a fibrinolytic heparin molecule and thrombomodulin, which prevents platelet aggregation and stops the coagulation cascade with nitric oxide and prostacyclin.
  • When endothelial injury occurs, the endothelial cells stop secretion of coagulation and aggregation inhibitors and instead secrete von Willebrand factor, which causes platelet adherence during the initial formation of a clot.
  • Within twenty seconds of an injury in which the blood vessel's epithelial wall is disrupted, coagulation is initiated.
  • Prothrombin, thrombin, and fibrinogen are the main factors involved in the outcome of the coagulation cascade.

• Anticoagulants

  • An anticoagulant is a substance that prevents coagulation (clotting) of blood.

• Withdrawing Blood

  • The most likely additive to cause trouble is EDTA, which will affect the coagulation time assays and by chelating some of the metal ions may interfere with some of the biochemistry results (especially potassium).
  • The blue tube contains citrate, a reversible coagulant, and is used for coagulation assays.

• Components of Blood

  • These membrane-bound cell fragments lack nuclei and are responsible for blood clotting (coagulation).
  • Platelets secrete factors that increase local platelet aggregation (e.g., thromboxane A), enhance vasoconstriction (e.g., serotonin), and promote blood coagulation (e.g., thromboplastin, fibrinogen).

• Clot Retraction and Repair

  • Clot retraction is dependent on the release of multiple coagulation factors released at the end of the coagulation cascade, most notably factor XIIIa crosslinks.

• Hemostasis Disorders

  • The most common blood disorders involve defects in the amount or activity of factors involved in coagulation.
  • The most common blood disorders, Von Willebrand disease, hemophilia, and Factor V Leiden thrombophilia, all involve defects in the amount or activity of factors involved in coagulation.