Haemostasis, Thrombosis and Embolism

Question 1

What is haemostasis?

Answer 1

Physiological process initiated when there is damage to a blood vessel. Rapid formation of solid plug at injury site to stop haemorrhage. Formed from platelets, fibrin, and RBCs

Question 2

What are the steps of haemostasis?

Answer 2

1. Endothelial injury leads to adhesion and aggregation of platelets. Adhere to collagen by vWF and RBCs becomes enmeshed (loose plug).
2. Exposure of tissue factor initiates coagulation cascade = forms insoluble fibrin.
3. Fibrin stabilises loose platelet plug, forming stable plug.

Question 3

What is fibrinolysis?

Answer 3

Activated by same injury as haemostasis. Plasmin formed which breaks down insoluble fibrin to soluble products. Ensures haemostasis is regulated and limited to injury site.

Question 4

What is thrombosis?

Answer 4

Inappropriate activation of haemostasis overwhelming fibrinolysis. Thrombus formation, made of platelets, fibrin and RBCs.

Question 5

What is the difference between a thrombus and a clot?

Answer 5

1. T - RBCs, C - no RBCs
2. T - within CVS, C - outside CVS
3. T - flowing blood, C - stationary blood

Question 6

What is Virchow’s triad?

Answer 6

1. Endothelial injury
2. Abnormal blood flow
3. Hypercoagulability

Question 7

What causes endothelial injury which can initiate thrombosis?

Answer 7

1. Atherosclerosis
2. Vasculitis
3. Direct trauma

Question 8

What causes abnormal blood flow which can initiate thrombosis?

Answer 8

1. Turbulence - atherosclerosis, artificial valves, stents, implanted devices.
2. Stasis - recent surgery, trauma, immobilisation, aneurysms.

Question 9

What causes hypercoagulability which can initiate thrombosis?

Answer 9

1. Too many RBCs - polycythaemia, thrombocytosis

2. Coagulation factor defects - hereditary, acquired

Question 10

What are the most important risk factors for thrombosis in an artery vs thrombosis in a vein?

Answer 10

1. Artery - atherosclerosis

2. Vein - stasis and hypercoagulability

Question 11

What are the complications of thrombosis?

Answer 11

1. Partial occlusion of vessel at site of thrombosis
2. Complete occlusion of vessel at site of thrombosis
3. Embolism to distal site

Question 12

What can vessel occlusion cause?

Answer 12

Ischaemia which can cause infarction

Question 13

What is this describing?

Tissue dysfunction due to interference with blood flow to a tissue which is reversible.

Answer 13

Ischaemia

Question 14

What is this describing?

Tissue death/necrosis due to interference with blood flow to a tissue which is irreversible.

Answer 14

Infarction

Question 15

What is this describing?

Cell death due to a pathological process.

Answer 15

Necrosis

Question 16

What is an embolism?

Answer 16

The occlusion of a vessel by undissolved material that is transported in the blood.

Question 17

What are the types of embolism and what causes them?

Answer 17

1. Thromboemboli - atherosclerosis, turbulent blood flow
2. Fat/bone marrow - trauma to long bones
3. Air - nitrogen after diving, air admitting in surgery
4. Amniotic fluid in maternal circulation - ARDS and DIC
5. Tumour - breast and prostate

Question 18

Which artery will be occluded from an emboli originating in the venous system vs the arterial system?

Answer 18

1. Venous - pulmonary artery

2. Arterial - systemic artery