Cardiovascular Physiology Part I: Hemostasis

Question 1

Hemostasis

Answer 1

process of stopping bleeding

Question 2

Vascular Spasm

Answer 2

vasoconstriction of damaged arteries, arterioles - ⇓ blood flow (minutes to hours)

Question 3

Platelet plug formation

Answer 3

• platelets stick to damaged blood vessel, release chemicals (factors) which:
  a) cause more platelets to stick (+ve feedback)
  b) romote clotting
  c) begin healing
• neighbouring healthy endothelial cells release a chemical preventing spread of plug
• plug formation requires a prostaglandin - inhibited by aspirin

Question 4

3 Stages of clot formation

Answer 4

1. production of prothrombin activator by:
   i. extrinsic pathway – uses factors released by damaged tissues
   ii. intrinsic pathway - uses factors contained in blood
   - usually both occur together - require Ca2+, tissue, platelet and/or plasma factors
2. Prothrombin converted to thrombin
3. Fibrinogen converted to fibrin
   - Thrombin - +ve feedback to ⇑ its own formation

Question 5

Clot Retraction + Repair

Answer 5

• retraction – blood vessel edges pulled together

- repair - fibroblasts form new CT, new endothelial cells repair lining

Question 6

Fibrinolysis

Answer 6

• clot dissolution
• fibrin digesting enzyme = plasmin
• phagocytes then remove clots in clumps

Question 7

Thrombus

Answer 7

a stationary clot in an undamaged vessel

Question 8

Embolus

Answer 8

free floating clot

Question 9

Hemophilia

Answer 9

clotting abnormal/absent

-about 83% = type A - lack clotting factor VIII