55 Blood Clotting - PSL302Y1Y: Lecture 55, by French! Wed....

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Blood Clotting Outline - Case studies: clinical relevance - How is blood clotting regulated? - How is the clot removed after healing has taken place? Textbook: 558-565 (5E); 547-554 (4E) 1) Case Studies: Clinical Relevance 1. Dave is a 55 year old man who recently had a mild heart attack . His physician has prescribed one baby aspirin per day. 2. Kristy is 18 and a competitive Fgure skater. She has von Willebrand disease . She constantly worries about internal bleeding injuries. 3. Dylan has hemophilia A . His parents infuse him each week w/ factor VIII . 4. Jason is a 50-year old man who was taken to the hospital b/c he was having vision pbms, weakness in one arm & a severe headache . His doctor conFrms that he has just had a stroke caused by a blood clot & quickly administers tissue plasminogen activator (tPA) . Recall: Hematopoiesis - Stem cells in bone marrow : enter diff diffation pathways depending on cytokines Platelets are needed for blood clotting - Megakaryocytes (multinucleated cells) - ±ragment into platelets: critical for blood clotting - Half-life of platelets = 10 days - Thrombopoietin (growth factor for platelets) # platelets PSL302Y1Y: Lecture 55, by ±rench Wed. Mar. 2, 2011 1 of 7
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2) How is blood clotting regulated? - Start : damage to wall of blood vessel = collagen exposed start phases 1-3 = tissue factor exposed start phases 2-3 Overview: 3 phases 1. Vascular phase = vasoconstriction a. Exposed collagen platelets adhere = release platelet factors 2. Platelet phase = creation of loose platelet plug a. Exposed collagen& tissue factor = coagulation cascade b. Platelets aggregate temporary hemostasis c. Alongside phase 3: reinforces platelet plug w/ Fbrin 3. Coagulation phase = creation of reinforced platelet plug (clot) a. Thrombin formation converts Fbrinogen to Fbrin b. Allow for cell growth & tissue repair; Fbrin slowly dissolved by plasmin = clot dissolves 1. Vascular phase 2. Platelet phase 3. Coagulation phase Figure 16.10 e animation at: tp://health.howstuffworks.com/adam- 0077.htm 1. Vascular phase = vasoconstriction - Local neurogenic & myogenic control = vascular spasm vasoconstriction - Prolonged by locally produced factors: - Serotonin : released by platelets - Endothelin-1 : released by endothelial cells - Thromoboxane A 2 : released by platelets PSL302Y1Y: Lecture 55, by ±rench Wed. Mar. 2, 2011 2 of 7
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2. Platelet phase = activation of platelets loose platelet plug (1) Exposed collagen activates platelets (inactive except in response to tissue damage) - Via von Willebrand factor ( present in blood): binds to exposed collagen - Cross-links it to platelets (2) Factors released from platelets
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This note was uploaded on 03/27/2012 for the course PSL 301 taught by Professor Mackayfrench during the Winter '12 term at University of Toronto- Toronto.

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55 Blood Clotting - PSL302Y1Y: Lecture 55, by French! Wed....

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