PSL201Y1 Lecture 15: Blood & Immunity 2
Document Summary
Blood and immunity 2: blood clotting (textbook: pages 441-445) Case study: dilan has hemophilia a; he is regularly infused with blood clotting factor viii. 3rd step (note: hemophilia b due to deficiency in factor ix) factor 9: explanation: Cause: x-linked recessive trait; deficiency in factor viii. Mechanism: factor viii forms a complex with factor ix to activate factor x. Platelets (or thrombocytes) needed for blood clotting: colorless, cell fragments. Organelles and granules: 100,000 500, 00/ l blood. Important in hemostasis (platelet plug: granules containing secretory products. Platelets formed from megakaryocytes: cytoplasmic fragments derived from megakaryocytes, thrombopoietin stimulates production of megakaryocytes, platelet half-life 10 days. What is hemostasis: hemostasis = stopping bleeding from a broken blood vessel, the arrest bleeding from a broken blood vessel. Three phases of hemostasis: 3 phases, vascular spasm, platelet plug formation, blood coagulation (clotting) Injury stimulates vasoconstriction leading to decrease in blood flow: reduces blood loss but does not stop bleeding.
