Hygiene Atlas

Atlas · Plate IV · Physiology · 04

Blood and hemostasis

Bleeding stops in stages: the vessel constricts, platelets form a plug, the coagulation cascade builds fibrin, and fibrinolysis later clears the clot. Vitamin K is needed for clotting factors II, VII, IX and X, which is why warfarin works and why it is monitored by INR, usually kept at 2-3. Hemophilia A and B are deficiencies of factors VIII and IX.

High-yield facts · 6

  1. Normal adult platelet count is about 150,000-450,000 per microliter.S49
  2. Hemostasis steps: vascular spasm, platelet plug, coagulation cascade, then fibrinolysis.S49
  3. Vitamin K is needed for clotting factors II, VII, IX and X; warfarin blocks vitamin K recycling.S49S51
  4. INR around 1.0 is normal; the usual therapeutic range on warfarin is 2-3 (2.5-3.5 for some mechanical valves).S57
  5. Hemophilia A is factor VIII deficiency; hemophilia B is factor IX deficiency.S49
  6. Red blood cells live about 120 days.S49

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