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NormalHemostasis
lecture 19 sarode
| Question | Answer |
|---|---|
| hemostasis | process through which the body stops hemorrhage from a damaged vessel |
| primary hemostasis | process by which plts and vWF initiate clotting. 3 steps: plt adhesion, secretion and plt aggregation |
| step 1: adhesion of plts | GPIb & subendothelial vWF attach to collagen GPIa/IIa -- binds subendothelial collagen |
| secondary hemostasis | clotting factors make cross-linked fibrin network to consolidate the initial plt plug made with primary hemostasis |
| tertiary hemostasis | fibrinolysis and dissolution of the clot |
| nl plt count | 150-450 billion plts/L |
| step 2: secretion of plts, after adhesion | activation of PLA2 to make TXA2; release of alpha granules that contain fibrinogen, vWF and thrombospondin; release of dense granules containing Ca++ & ADP |
| step 3: aggregation, after secretion | GPIIb/IIIa undergoes conformational change to be able to bind fibrinogen with high affinity |
| After which step does the plt go from discoid to conformation with many dendritic pseudopodia? | after initial adhesion (step 1) |
| plt count that qualifies as thrombocytopenia | < 100K per microliter of blood |
| plt count that puts pt at risk for spontaneous bleeding | < 10K per microliter of blood |
| sx seen with plt dysfunction (thrombocytopathies like von Willebrand dz) | mucocutaneous bleeding --> GI bleeds, epistaxis, menorrhagia, petechiae and pupura, urinary tract bleeding |
| methods for acquired plt dysfunction | herbs, fish oils, some dietary supplements, ASA, Plavix |
| liver makes all coagulation factors except for ______ | factor VIII |
| how does FVIII travel | carried and stabilized by vWF in the plasma |
| coagulation factors are serine protease zymogens that must be cleaved and activated | |
| vitamin K dependent factors | Factors II, VII, IX and X must be gamma carboxylated so Ca++ can associate and they can become fully active, capable of binding phospholipid surfaces |
| heat-labile coagulation factors | V and VIII |
| hemophilia A | factor VIII deficiency (1:5000) |
| hemophilia B | factor IX deficiency (1:25,000) |
| antithrombin's effects are potentiated by what? | heparan sulfate (Heparin in clinic enhances thousands fold), dermatan sulfate and chondroitin sulfate |
| Factor VII has shortest half-life of 3-6 hrs | |
| vonWillebrand dz | most common congenital bleeding disorder with mucocutaneous bleeding, decreased Factor VIII binding |
| Pt on heparin will have abnormally low antithrombin levels |
Created by:
sirprakes
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