Thrombosis, embolism, ischemia and infarction.

Question 1

What is thrombosis?

Answer 1

Thrombosis is a solid mass of blood constituents formed within intact vascular system during life. (formation of a blood clot, which often causes obstruction)

Question 2

What is an embolus?

Answer 2

A mass of material in the vascular system able to become lodged within a vessel and block it. (This may be a blood clot (thrombus), a fat globule or a bubble of air or other gas.

Question 3

How does a thrombus occur?

Answer 3

The endothelium is damaged.
Platelets stick to collagen under endothelium lining.
Platelets release chemicals causing more platelets to stick together (positive feedback)
Laminar flow is disrupted and rbc are trapped in the platelets.
Fibrinogen becomes fibrin, a protein which holds this mass together.

Question 4

What 3 factors predispose to thrombosis (Virchows triad)

Answer 4

1. Change in vessel wall (endothelial cell damage)
2. Change in blood flow (laminar flow to turbulent flow)
3. Change in constituents of blood (e.g. overly sticky platelets)

Question 5

How can you prevent thrombosis?

Answer 5

1. elastic stockings (increase blood flow)
2. Aspirin - anti-platelet drug - over 50s recommended to take 75mg of aspirin daily.
3. exercise

Question 6

When is deep vein thrombosis a problem?

Answer 6

Blood is the veins move slower so are more likely to hit the endothelial cell wall (less laminar flow) so there can be a slow thrombus formation. In hospitals this is a risk as patients sit/lie in bed and don’t have as much blood flow.

Question 7

What is ischaemia?

Answer 7

Ischaemia is reduction of blood flow to an organ or part of the body.
(no cell death)

Question 8

What is infarction?

Answer 8

Infarction is the obstruction of blood supply to an organ or tissue resulting in cell death.
A subset of ischaemia - severe ischaemia.

Question 9

What is reperfusion injury?

Answer 9

This is damage to a tissue when blood returns to a tissue after a period of ischaemia/lack of oxygen. Cells produce radicals causing damage?

Question 10

What is an end artery?

Answer 10

An artery that is the only oxygen supply to a portion of tissues/organ. e.g. heart

Question 11

examples of body parts with 2 blood supplies

Answer 11

Lungs

Circle of wills in brain