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Lecture 26
Introduction to Disorders of Coagulation & Hemostasis
Question | Answer |
---|---|
What occurs during primary hemostasis? | (1) Vascular phase: endothelial cell changes (2) Platelet phase: plt attach to injury site, formation of plt plug, support of coagulation reactions |
What occurs during secondary hemostasis? | The coagulation cascade |
What is the physical response of blood vessels to injury? | 1) vasocontriction via both neural stimulation and chemical vasocontrictors 2) elastic recoil of blood vessels |
What is the anticoagulant effect of PGI2? | Deters platelet aggregation |
What is the anticoagulant effect of thrombomodulin? | Binds thrombin and activates Protein C |
What is the endothelial cell response to vessel injury? | Subendothelial collagen and VWF binding sites exposed; Thrombomodulin and heparan is stripped away; PGI2 and tPA are no longer produced; tissue factor is exposed to Factor VII, initiating the coagulation cascade |
What proteins are required for platelet binding to the site of vessel injury? | 1) Von Willebrand Factor (VWF) 2) Platelet GP1b |
(T or F) Platelet aggregation requires platelet activation and energy requiring process. | True. |
What platelet surface receptor is required for platelet aggregation? | Glycoprotein IIbIIIa receptor |
What platelet surface phospholipid is required for efficient enzymatic coagulation reactions? | Phosphotidyl serine |
What enzyme promotes reversal of Phosphotidyl choline (PC)/Phosphotidyl serine (PS) in the platelet bi-lipid membrane? | Flipase |
What is the importance of Calcium in coagulation? | Catalyzes reactions by promoting attachment of enzymes and zymogens to phopholipid surface |
What are the co-factors of the coagulation cascade? | Factor VIII, V, III (Tissue Factor) |
What are the enzymes of the coagulation cascade? | Factors XIII, XII, XI, X, IX, VII, and II |
What is the function of thrombin? | 1)cleaves fibrinogento fibrin 2)activates plts 3)activates factor XI 4)activates factor XIII to XIIIa 5)activates Protein C when bound to thrombomodulin 6)at low levels-enhances FV and FVIII function 7)at high levels-destroys FV and FVIII |
What laboratory study monitors the extrinsic pathway of the coagulation cascade? | Protime (PT) |
What laboratory study monitors the intrinsic pathway of the coagulation cascade? | aPTT |
What are the initiatiors of the coagulation cascade used in the lab aPTT assay? | FXII, prekallikrein, and high molecular weight kininogen (HMWK) |
(T or F) Deficiencies of FXII, Prekallikrein, and HMWK prolong the aPTT test but do not cause bleeding. | True. |
What coagulation factors require Vitamin K? | Factor VII, IX, X, II |
What is the importance of Vitamin K in coagulation? | The enzymes Factor VII, IX, X, and II require gamma-carboxylation by Vit K dependent pathway. Carboxyl residues help enzymes bind to the surface. |
What anticoagulant drug interferes with Vit K dependent pathways in the coagulation cascade? | Coumadin (warfarin) |
What are some common causes of Vitamin K deficiency? | 1) poor intake 2) biliary disease 3) antibiotics interfering with Vit K metabolism in the gut |
With coumadin therapy, which coagulation enzyme is inhibited first? | Factor VII |
What coagulation factors are monitored by PT? | Measures Factor VII, V, X, II, and fibrinogen |
For the lab PT assay, what initators are added to the patient's blood sample for clot formation? | Thromboplastin (Tissue Factor and phospholipids) and calcium |
What laboratory assay is used to monitor coumadin therapy? | Prothrombin Time (PT) |
What laboratory assay is used to monitor FVII deficiency? | Prothrombin Time (PT) |
A laboratory assay of clotting factors used to monitor the intrinsic pathway of coagulation. | aPTT (activated partial thromboplastin time) |
What laboratory study monitors heparin therapy? | aPTT |