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IV9 - VI Hemostasis(stoppage of blood flow after damage A...

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Physiology of Blood IV. Platelets (thrombocytes - "clotting") A. General Characteristics 1. very small, 2-4 microns in diameter 2. approximately 250-500,000 per cubic millimeter 3. essential for clotting of damaged vasculature 4. thrombopoietin - regulates platelet production B. Formation of Platelets hemocytoblast-> myeloid stem cell-> megakaryoblast-> promegakaryocyte-> megakaryocyte-> (large multilobed nucleus) platelets (anucleated parts of megakaryocyte cytoplasm) V. Plasma (the liquid part of blood) A. General Characteristics 1. plasma makes up 55% of normal blood by volume 2. water is 90% of the plasma by volume 3. many different SOLUTES in the plasma a. albumin - pH buffer & osmotic pressure b. globulins - binding proteins & antibodies c. clotting proteins - prothrombin & fibrinogen d. other proteins - enzymes, hormones, others e. nutrients - glucose, fatty acids, amino acids, cholesterol, vitamins f. electrolytes - Na + , K + , Ca ++ , Mg ++ , Cl - , phosphate, sulfate, bicarbonate, others
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Unformatted text preview: VI. Hemostasis (stoppage of blood flow after damage) A. General Characteristics 1. vascular spasms (vasoconstriction at injured site) 2. platelet plug formation (plugging the hole) 3. coagulation (blood clotting - complex mechanism) B. Vascular Spasms 1. first response to vascular injury - VASOCONSTRICTION is stimulated by: a. compression of vessel by escaping blood Physiology of Blood b. injury "chemicals" released by injured cells c. reflexes from adjacent pain receptors C. Formation of a Platelet Plug 1. damage to endothelium of vessel 2. platelets become spiky and sticky in response 3. platelets attach to damaged vessel wall to plug it 4. platelets produce thromboxane A2 - granule release 5. serotonin release enhances vascular spasm 6. ADP - attracts and stimulates platelets at site 7. prostacylin - inhibits aggregation at other sites...
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