TThrombosis, Emboli and Atheroma

Question 1

What are the 4 zones of a platelet?

Answer 1

Peripheral
Sol gel
Organelle
Membrane

Question 2

What constitutes the peripheral zone of platelets?

Answer 2

Rich in glycoproteins needed for platelet adhesion and aggregation

Contains platelet Factor 3 - which promotes clotting during aggregration

Question 3

What constitutes the Sol-gel zone of platelets?

Answer 3

Contains microtubule and microfilaments

Question 4

What constitutes the Organelle zone of platelets?

Answer 4

• Contains alpha granules which contain:
  factor VIII, V,
  fibrinogen
  fibronectin
  platelet derived growth factor
  chemotactic factors
• Contains dense bodies that contain ADP, 5HT and calcium

Question 5

What constitutes the membrane zone of platelets?

Answer 5

Contains the dense tubular system responsible for platelet contractile function and PG synthesis

Question 6

Name examples of thrombotic factors

Answer 6

• vWB factor (produced by endothelial cells allowing PLT adherence)
• Binding factors IXa and X
• Factor V
• Thromboplastin (endothelium)

Question 7

Name examples of anti-thrombotic factors

Answer 7

• tPA (converts plasminogen to plasmin which digests the thrombus)
• Anti-thrombin III (inactivates thrombin and factor XIIa, XIa, Xa and IXa)
• Thrombomodulin (alters thrombin to activate protein C)
• Protein C destroys factors V and VIII

Question 8

What is the inheritance of Protein C deficiency?

Answer 8

AD - clinically affected individuals are heterozygous, with a protein C concentration of 50%

Question 9

What is Protein C?

Answer 9

A Vitamin K dependent serine protein that potently inhibits factors Va and VIIIa

Question 10

What is the prevalence of protein C deficiency in patients with venous thrombosis?

Answer 10

6-8%

Question 11

What is factor V leiden mutation?

Answer 11

It results in the resistance of factor V to breakdown by protein C

Question 12

What % of the white populations are carriers of factor V Leiden?

Answer 12

5 % - most common inherited thrombophilia

Question 13

What is protein S?

Answer 13

A Cofactor in the inactivation of factor Va and VIIIa by activated protein C

Question 14

What is the prevalence of protein S deficiency in young patients?

Answer 14

5-8%

It is AD

Question 15

What is the prevalence of anti-thrombin III deficiency in patients with venous thrombosis?

Answer 15

0-5%

Question 16

What is Virchovs triad?

Answer 16

1. Change in blood flow e.g. venous stasis, arrhythmia, valvular disease
2. Change in vessel wall e.g. atherosclerosis, trauma, inflammation, neoplasia
3. Change in blood constituents e.g. increased PLTs or altered PLT function

Question 17

Where can AIR emboli originate from?

Answer 17

Can occur during thyroid surgery

Question 18

Where can SEPTIC emboli originate from?

Answer 18

Subacute bacterial endocarditis leading to Roth spots

Question 19

Where can AMNIOTIC emboli originate from?

Answer 19

Complication of delivery particularly if the foetus is manipulated

Question 20

How are atheroma formed?

Answer 20

• Vascular endothelial cell damage
• Platelets adhere to the endothelium and promote SM cells within the vessel wall intima to proliferate
• The stimulation factor is platelet derived growth factor
• Intracellular and extracellular lipid accumulate at the site due to breakdown in the endothelial cell barrier - this forms a FIBROPIPID/ATHEROSCLEROTIC PLAQUE

Question 21

What is a true aneurysm?

Answer 21

True aneurysms contain all three layers of the vessel wall.

Question 22

What is a pseudoaneurysm?

Answer 22

A false aneurysm or pseudoaneurysm is a haematoma that forms outside the vessel wall, and is contained by surrounding tissues, as a result of a leaking artery.

Question 23

What is a Berry aneurysm?

Answer 23

Berry aneurysm is found in the Circle of Willis and is caused by vessel wall deficiency.

Question 24

What is a Saccular aneurysm?

Answer 24

Saccular aneurysm involves only part of the circumference of the vessel wall

Question 25

What is a fusiform aneurysm?

Answer 25

fusiform aneurysm involves the entire circumference of a vessel wall

Question 26

Why does a dissecting aneurysm occur?

Answer 26

Dissecting aneurysm occurs in arterial media deficiency as in Marfan’s syndrome.