Haemostasis and thrombosis

Question 1

What is haemostasis?

Answer 1

• the body’s response to stop bleeding and loss of blood
• blood vessels restrict to stop perfusion
• coagulation cascade activates
• fibrin clot forms

Question 2

How is the coagulation system regulated?

Answer 2

• thrombin positively feeds back on 5, 8 and 11
• can be inhibited by: protein C/S, alpha 1 antitrypsin etc
• fibrinolysis: break down of fibrin by plasmin
• many other feedback mechanisms
• ref therapeutics such as heparin, streptokinase etc

Question 3

What is thrombosis?

Answer 3

formation of a solid mass of blood within the circulatory system during life

Question 4

What factors influence thrombosis?

Answer 4

• Virchow’s triad: hypercoagulability, stasis, endothelial damage
• arterial: lines of zahn, pale, granular, fewer cells
• venous: deep red, soft, gelatinous, higher cell count

Question 5

What are the effects of arterial and venous thrombosis?

Answer 5

• arterial: ischemia, infarction, depends on collateral circ.
• venous: congestion, oedema, ischemia, infarction

Question 6

What are the possible outcomes of thrombosis?

Answer 6

• lysis of the clot
• propagation: increased growth of clot
• organisation: ingrowth of fibroblasts and capillaries
• recanalization: blood flow re-established
• embolism: part of clot breaks off, lodges at distant site

Question 7

What is an embolism?

Answer 7

the blockage at a blood vessels by a solid, liquid or a gas