48 - Vascular Pathology II

Question 1

Example of a factor on platelets, and its ligand on vascular endothelium

Answer 1

GP1b on platelets sticks to exposed Von Willebrand factor

Question 2

What do platelets do when activated?

Answer 2

Change shape, release granules (factors, fibrinogen)

Question 3

Thrombomodulin

Answer 3

Changes thrombin from activator of clotting to an inhibitor

Question 4

Effector of fibrinolysis

Answer 4

Tissue plasminogen activator (tPA)

Question 5

Mechanism of tissue plasminogen activator action

Answer 5

Tissue plasminogen activator binds to fibrin, activates plasmin. Plasmin degrades fibrin.

Question 6

Thrombus

Answer 6

A blood clot within an intact, living cardiovascular system.

Question 7

Contents of a thrombus

Answer 7

RBC, WBC, platelets

Question 8

Appearance of a thrombus

Answer 8

Red and white stripes (layers of RBC and platelets+fibrin) - called ‘lines of Zahn’.

Question 9

Difference in appearance between arterial and venous thrombi

Answer 9

Arterial are white.

Venous are red.

Question 10

Why do arterial thrombi appear white?

Answer 10

Greater proportion of platelets and fibrin.

Question 11

Why do venous thrombi appear red?

Answer 11

Higher proportion of RBC

Question 12

What are arterial thrombi mostly associated with?

Answer 12

Endothelial dysfunction or damage

Question 13

What are venous thrombi mostly associated with?

Answer 13

Blood stasis, hypercoagulability

Question 14

Useful drug for preventing arterial thrombi

Answer 14

Aspirin (interferes with platelet thromboxane production)

Question 15

Useful drug for preventing venous thrombi

Answer 15

Warfarin (interferes with coagulation cascade)

Question 16

Outcome of laminar flow in blood vessels

Answer 16

Blood cells don’t touch vascular wall

Question 17

Why do thrombi form?

Answer 17

Virchow’s triad of factors influencing clotting:

1) Endothelium (EG: injury)
2) Blood flow (EG: non-laminar flow)
3) Blood composition (EG: hypercoagulability)

Question 18

How might endothelial abnormality occur (Virchow 1)

Answer 18

Endothelial activation or dysfunction from:

Inflammation (EG: from smoking, infection, toxins, hypertension, etc)

Question 19

How can abnormal blood flow (Virchow 2) lead to thrombus formation?
1)
2)
3)

Answer 19

Turbulence, stasis, or loss of laminar flow:

1) Endothelium is activated
2) Platelets come into contact with vascular wall
3) Allows any activated clotting factors to accumulate, initiate cascade

Question 20

How can abnormal blood coagulability (Virchow 3) come about?

Answer 20

1) Genetic (primary) - EG: Factor V Leiden

2) Non-genetic (secondary) - Oestrogen (contraceptive pill, pregnancy), cancer, smoking, obesity, age

Question 21

Factor V Leiden

Answer 21

Mutant of factor V protein in coagulation cascade. Confers hypercoagulability.
If heterozygous, 5x risk of thrombosis.
If homozygous, 50x risk of thrombosis.

Question 22

Examples of secondary risk factors for thrombosis
1)
2)
3)
4)
5)
6)

Answer 22

1) Prolonged immobilisation
2) Myocardial infarct
3) Atrial fibrillation
4) Tissue injury (EG: surgery, burn, fracture)
5) Cancer
6) Smoking

Question 23

Things that can happen to a thrombus
1)
2)
3)
4)

Answer 23

1) Dissolution - Fibrinolysis (with tissue plasminogen activator, protein C and S). Becomes less likely with age.
2) Organisation and recanalisation (granulation tissue formation
3) Propagation (grows)
4) Embolisation

Question 24

Embolus

Answer 24

Intravascular mass carried in the bloodstream (solid, liquid or gaseous- EG the bends)

Question 25

Examples of emboli causing disease
1)
2)

Answer 25

1) Pulmonary embolus

2) Arterial thromboembolism

Question 26

Where do emboli that result in pulmonary emboli often forM?

Answer 26

Usually in legs as a DVT

Question 27

Where do emboli that result in arterial thromboembolism often form?

Answer 27

Usually from atheroma (EG: atherosclerosis) or heart

Question 28

Outcomes of pulmonary embolism

Answer 28

Can be asymptomatic, cause transient hypoxia, sudden death

Question 29

Where do emboli causing pulmonary embolism often lodge?

Answer 29

Travels through right heart, lodges in pulmonary arteries.

Question 30

What does the formation of an arterial thromboembolism often involve?

Answer 30

Turbulence and/or platelets adhering to a dysfunctional blood vessel surface (EG: atherosclerosis, myocardial infarct, atrial fib)

Question 31

Where is it rare for emboli from the heart to lodge?

Answer 31

In the coronary arteries

Question 32

Difference between ischaemia and infarction

Answer 32

Ischaemia means ‘not enough blood supply.’

Infarction is tissue death as a result of too little blood supply

Question 33

Difference between ischaemia and hypoxia

Answer 33

Ischaemia is too little blood supply.
hypoxia is too little oxygen.
EG: If severely anaemic, can have hypoxia without ischaemia.

Question 34

Examples of acute ischaemia
1)
2)

Answer 34

1) Coronary thrombosis leading to myocardial infarct.

2) Shock, reducing blood supply to everything

Question 35

Examples of chronic ischaemia
1)
2)

Answer 35

1) Atherosclerotic disease leading to atrophy of lower limbs
2) Renal artery stenosis leading to renal atrophy

Question 36

Most common cause of infarction

Answer 36

Arterial occlusion

Question 37

Time taken for neurons to die from hypoxia

Answer 37

3-4 minutes

Question 38

Two appearances of infarctions

Answer 38

1) Red infarction

2) White infarction

Question 39

Red infarction

Answer 39

When there is haemorrhage in infarcted tissue

Question 40

Situations that could lead to red infarction
1)
2)
3)
4)

Answer 40

1) Dual blood supply to an organ (EG: Lungs)
2) Collateral blood supply (EG: intestine)
3) Venous infarction (EG: testicular torsion)
4) Reperfusion (common in emboli to the brain)

Question 41

How can reperfusion lead to a red infarct?

Answer 41

Infarction of tissue causes necrosis, breakdown of structure.
Blockage of artery is removed, blood enters now-damaged organ and leaks out into surrounding tissues.

Question 42

Pale infarction

Answer 42

When there is no bleeding in infarcted tissues

Question 43

When are pale infarcitons more common?

Answer 43

Due to a blocked end artery

Question 44

Why can an infarct lead to a thrombosis?

Answer 44

Abnormal, inflamed endothelium overlies infarct.