ANP 1105 Lecture Notes - Lecture 4: Blood Transfusion, Quinone, Protein C

• School: University of Ottawa
• Department: Anatomy and Physiology
• Course: ANP 1105
• Professor: Frank Feiner

Document Summary

Formation of platelets: cell fragments essential for blood clotting, arise from hematopoietic stem cell in bone marrow. Analogous to erythropoietin: repeated mitosis/no cytokinesis (division of cytoplasm) leads to megakaryocyte, a single cell with a huge nucleus, megakaryocyte ruptures: platelet fragments leads to plasma. 2-4 um diameter, 150-400,000/ul of blood (rbc: 7-8 um diameter, 4-6 million/ul. 3 steps include: vascular spasm: smooth muscle contracts, causing vasoconstriction, platelet plug formation: injury to lining of vessel exposes collagen fibers; platelets adhere. Platelets release chemicals that make nearby platelets sticky: platelet plug forms: coagulation: fibrin forms a mesh that traps red blood cells and platelets, forming the clot. Initially, damaged blood vessel contracts (vasoconstriction: triggers: Reflexes initiated by local pain receptors: spasm mechanism most effective in smaller vessels, can significantly reduce blood loss for 20-30 min. Allows time for platelet plug formation and coagulation to begin.