Hemostasis Flashcards
First cellular evidence that there is a break in the endothelium to stop the bleeding
Platelet system
Four major steps in hemostasis
Vasoconstriction
Formation of platelet plug
Blood clot
Growth of fibrous tissue
System which dissolves the clot
Fibrinolytic system
First response to injury
Vasospasm = localized vasoconstriction
Protein which causes platelets to contract
Thrombosthenin
Molecule responsible for platelet aggregation
Von Willenbrand Factor
Receptor responsible for adhesion of platelets to collagen and vessel wall to form platelet plug
Gp1a
Factors affecting platelet activation
Von Willenbrand
ADP
Ca2+
Thromboxane
Stabilized by the formation of an organized fibrin clot
Hemostatic plug
Vitamin K dependent factors
FII, FVII, FIX, FX
Provided by endothelium and platelets responsible for conversion of precursor proteins to active proteases
Ca, phospholipid surfaces
Converts soluble fibrinogen into fibrin
Thrombin
Needed along with fibrin to form a mesh-like net to catch blood cells
FXIII
Pathway which initiates coagulation cascade
Extrinsic pathway
Expressed in the extrinsic pathway following injury
Tissue Factor
Causes activation of FIX and FX in the extrinsic pathway
Binding of TF and FVII
Activates thrombin from prothrombin
FXa
Triggered by shortage of FXa and thrombin
Intrinsic Pathway
Pathway activated in the presence of thrombin
Intrinsic Pathway
Coagulation factor enhanced in the intrinsic pathway
FXa
Inhibits thrombin formation and FXa
Antithrombin III
Inhibits the formation of fibrin clot by inactivating FVa and VIIa in the intrinsic pathway
Protein C, protein S
Binds to thrombin, decreases ability to produce fibrin
Thrombomodulin
Affect posttranslational modification, cause dysfunctional fibrin clots
Vitamin K antagonists
Mechanism of heparin action
Inactivates thrombin and Xa
Proceeds upon plasminogen activation to degrade fibrin
Fibrinolysis
Blood composition
Vessel wall components
Blood flow
Virchow’s Triad
Thrombus vs Embolus
Thrombus - clot in an unbroken vessel
Embolus - object that blocks blood flow that can move through the vessel; may also be a thrombus or air bubble
Small pinpoint hematomas 1-2mm in diameter due to minor hemorrhage
Petechiae
Bruise about 1cm in diameter due to bleeding under the skin
Purpura
Another term for bruise
Ecchymoses
Deep seated collection of clotted blood in an organ, tissue, space, or cavity
Hematoma
Microcytic vs normocytic anemia
Microcytic - small and hyperchromic red blood cells
Normocytic - normal MCV but lowered hematocrit and Hb
Performance indicator measuring the intrinsic and common pathways of hemostasis
Activated partial thromboplastin time
Tests the efficacy of the extrinsic pathway of coagulation
Prothrombic time
Measures the time it takes for a clot to form; measure of fibrin formation
Thrombin time
Disorder characterized by Decreased fibrinogen activity
Dysfibrinogenemia
