USMLE

Blood Clotting

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Cardiovascular
  1. Cardiovascular Overview
  2. CO2 Transport
  3. Heart
  4. Cardiac Impulse
  5. Blood Pressure
  6. Arteries and Arterioles
  7. Veins and Venules
  8. Capillaries
  9. Circulation
  10. Blood
  11. Hemoglobin
  12. Blood Clotting
  • Blood Clotting (note: not high yield)
    • Function
      • Minimize blood loss and facilitate healing after injury
    • Process
      • Step 1: Platelets form a plug
        • Collagen outside of blood vessel chemically interacts with platelets and causes them to stick together (coagulate) at damage site
        • Prevents blood flow out of vessel
        • Bound platelets and endothelial cells release signals to recruit more platelets
      • Step 2: Fibrin forms a mesh
        • Platelet aggregation activates clotting factors
          • Cascade of activated factors called the Coagulation Cascade
        • Culminates in production of thrombin, which converts fibrinogen in plasma to fibrin
        • Fibrin strands polymerize and form mesh to hold platelets together, reinforces platelet plug