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HSF II Cardio IIR
HSF II Cardiovascular - Hemostasis
Question | Answer |
---|---|
Hemostasis | collection of events that stops bleeding by turning a portion of the fluid blood into a semi-solid clot or thrombus |
Two Aspects of Hemostasis | 1) anticoagulant activity 2) procoagulant activity |
Anticoagulant Activity | maintains blood in a fluid state while circulating within the vascular system, does not promote hemostasis, predominate and inhibit hemostasis in normal conditions |
Procoagulant Activity | promotes hemostasis, predominate in damaged blood vessels and hemostasis initiates, a clot forms |
Virchow's Triad | factors for thrombosis: 1. injuries to vascular endothelium, 2. alterations in normal blood flow, 3. alterations in the constitution of blood |
Causes of Abnormal Blood Flow | immobility, venous obstruction, varicose veins, atherosclerosis, atrial fibrillation |
Deep Vein Thrombosis (DVT) | when blood clot (thrombus) forms in one or more of the deep veins in your body, usually in the legs. because venous flow from muscle pump |
Causes of Changes in Blood Constitution | sepsis, chronic inflammation, hormonal changes/therapy, thrombophilia |
Most important factor for maintaining normal pro- and anti-coagulant balance | endothelial integrity |
von Willebrand Factor (vWF) | a procoagulant glycoprotein made by undamaged endothelium, binds and prevents the degradation of clotting factor VIII |
Cause of Hemostasis Initiation | when the balance of anticoagulants and procoagulants is shifted |
Three Phases of Hemostasis | 1) vascular spasm 2) platelet plug formation 3) coagulation (clotting) |
Vascular Spasm (Hemostasis) | smooth muscle contracts, causing vasoconstriction: a) pain, b) myogenic reflex, c) endothelins |
Platelet Plug Formation (Hemostasis) | injury to lining of vessel exposes collagen fibers, platelets adhere. Platelets release chemicals that make nearby platelets sticky, and platelets form the clot |
Pain (vascular spasm) | activates the sympathetic nervous system, increased sympathetic stimulation causes vasoconstriction |
Myogenic Reflex (vascular spasm) | direct response of smooth muscle to mechanical stimulation, stretch the muscle or deform it, causing mechanically gated ion channel |
Endothelins (vascular spasm) | cytokine proteins that constrict blood vessels. trauma to tunics increase endothelin production and shifts balance to vasoconstriction. |
Platelet Phase | second phase in hemostasis, subendothelial vWF exposed, platelets bind to vWF and the exposed collagen via one membrane receptor, fibrinogen binds to the other |
Platelet Release Reaction | aggregated platelets release 1) serotonin (5-HT) (vasoconstrictor) 2) ADP and 3) Thromboxane A2 (vasoconstrictor, eicosanoid). these all enhance platelet plug formation |