Thrombosis and Infarction

Question 1

Define clot

Answer 1

Solid mass of blood constituents formed after death

Question 2

Define thrombus

Answer 2

Solid mass of blood constituents formed in life

Question 3

3 predisposing factors (Virchows triad)

Answer 3

Changes in flow, change to vessel wall, changes in blood constituents

Question 4

Define embolism

Answer 4

Process of a solid mass in the blood being carried through the circulation until it causes an occlusion

Question 5

6 causes of embolus

Answer 5

Fat, air, thrombus, bacteria, amniotic fluid, tumour

Question 6

2 reasons clots are rare

Answer 6

Laminar flow (cells travel in centre of vessels and don’t touch the sides). Endothelial cells that line vessels are not ‘sticky’ when healthy

Question 7

2 stages of thrombosis

Answer 7

Platelet aggregation and clotting cascade

Question 8

Define ischaemia

Answer 8

Reduction in blood flow to a tissue without any implications

Question 9

Define infarction

Answer 9

Reduction in blood flow to a tissue to the point that it can not support the demands of the cells so they die

Question 10

3 organs with dual blood supply

Answer 10

Liver - portal venous and hepatic artery. Lung - pulmonary veins and bronchial arteries. Brains - Circle of Willis

Question 11

Describe the course of arterial thrombosis

Answer 11

Atheromatous plaque consisting of a slightly raised fatty streak, protrudes into lumen causing turbulence, this causes loss of intimal cells. Turbulence predisposes to fibrin deposition and platelet clumping. Collagen is exposed & platelets settle

Question 12

How are lines of Zahn formed?

Answer 12

Alternating layers of platelets and a fibrin meshwork in which RBC get trapped

Question 13

What initiates venous thrombosis?

Answer 13

Most begin at valves where there is natural turbulence, may be damaged by trauma, stasis or occlusion

Question 14

When is venous thrombosis most likely?

Answer 14

Post surgery, when blood pressure is allowed to fall, following a MI, immobilisation,

Question 15

What is thrombophlebitis?

Answer 15

When a thrombosed vein becomes inflamed

Question 16

What is phlebothrombosis?

Answer 16

When an inflamed vein becomes thrombosed

Question 17

Clinical signs of arterial thrombosis

Answer 17

Area of impaired supply becomes cold, pale and painful. Eventually the tissue dies and gangrene occurs

Question 18

Clinical signs of venous thrombosis

Answer 18

Tender, swollen and red

Question 19

Describe the structure of an atherosclerotic plaque

Answer 19

central lipid core, cap of fibrous tissue containing macrophages, mast cells and T lymphocytes

Question 20

What is a thrombotic cerebral infarction?

Answer 20

Arterial thrombus due to atheroma in any of the vessels supplying the brain

Question 21

What is a hypertensive stroke?

Answer 21

High blood pressure leads to atheroma and disruption of the autoregulation of cerebral circulation

Question 22

5 risk factors for atheroma

Answer 22

Male, increased blood pressure, increased age, smoking, diabetes

Question 23

What is a fatty streak?

Answer 23

Yellow elevation of intimal lining made up of lipid laden macrophages

Question 24

3 stages of formation of atheroma

Answer 24

Fatty streak formation - lipids deposited, inflammation, increased permeability and white blood cell recruitment.
Fibrolipid plaque formation, lipid stimulates formation of fibrocollagenous tissue - thinning of muscular media.
Complicated atheroma - prone to rupture, may be calcified, rupture activates clot/thrombosis -> MI/angina