ch5.1 blood clotting

• 1. Vasoconstrict:

  • muscles in walls of small arteries that have been injured constrict immediately to reduce blood flow and blood loss
• 2. Platelet plug

  • platelets stick to the rough surface; sticking platelets attract others
  • plug is built up, reduces blood loss
  • platelets release vasoconstrictors - enhance constriction of damaged vessels
• 3. Coagulation

  • large number of chemical substances (clotting factors) involved
  • formation of threads of an insoluble protein (fibrin) forms a mesh
  • called 'thrombus'
• 4. Clot retraction

  • network of threads contracts, becoming denser and stronger - pulls edges of damaged vessel together
  • fluid known as 'serum' is squeezed out
  • clot dries - forms scab