Hemostasis Flashcards
Hemostasis
definition
the arrest of bleeding from a broken blood vessel
Vascular Spasm
when a vessel is damaged, the smooth muscle cells in the wall contract immediately, slowing the blood flow and minimizing blood loss
ADP
role in platelet plug
- released by activated platelets and endothelial cells at injury site
- causes nearby platelets to become sticky
Thromboxane A2
role in platelet plug
- released by activated platelets
- stimulates platelet aggregation and release of ADP
- enhances vascular spasms
Serotonin
role in platelet plug
assists thromboxane A2 in stimulating vasoconstriction
Platelet Derived Growth Factor (PDGF)
a peptide that promotes vessel repair by stimulating the division of endothelial cells, smooth muscle cells, and fibroblasts
Prostocyclin
- a prostoglandin secreted by endothelial and white blood cells
- opposes actions of thromboxane A2
- a powerful inhibitor of platelet adhesion and release (anticoagulant)
Antithrombin III
inhibits several different procoagulants, including thrombin
Heparin
- released by the basophils, mast cells, and endothelial cell
- it accelerated the activation of antithrombin III
Tissue Plasminogen Acitvator (t-PA)
- secreted by endothelial cells
- it converts plasminogen to plasmin which enzymatically degrades fibrin (clots)
Fibrinolysis
- clot destroyed by breakdown of fibrin
- plasminogen is converted to plasmin
Trigger of Extrinisic Pathway
- damaged tissue produces tissue thromboplastin (tissue factor)
- this activates factor VII
Trigger of Intrinsic Pathway
- damaged cells contact collagen
- this activates factor XII
Coagulation Stage 2
prothrombinase converts prothrombin to thrombin
- in presence of calcium
Coagulation Stage 3
thrombin converts fibrinogen to fibrin
- in presence of calcium
Prothrombinase
enzyme that converts prothrombin to thrombin
Fibrinogn
plasma protein formed by the liver that is converted to fibrin
Prothrombin
plasma protein formed by the liver that is converted to thrombin
Thromboplastin
- a tissue protein that is a complex mixture of lipoproteins and phospholipids released from surface of damaged cells
- also known as tissue factor
Plasminogen
an inactive plasma enzyme that is activated to plasmin
Warfarin
depresses synthesis of several clotting factors by blocking use of vitamin K by liver
Streptokinase
converts uncomplexed plasminogen to plasmin
Urokinase
activates plasminogen, and directly degrades fibrin
EDTA and CPD
removes calcium from plasma
