Physiology

Question 1

Main vasoconstrictor factors

Answer 1

1. Local myogenic spasm
2. Factors released by traumatised tissue / plt
   • Plt releases thromboxane A2

Question 2

Antithrombin III

Answer 2

Inhibits factors IX / X / XI / XII

Inactivates plasmin + kinin system

Inhibits complement activation

Neutralizes thrombin + Xa

Question 3

Thrombomodulin

Answer 3

Produced by all endothelial cells on their surfaces (except in cerebral microcirculation)

Binds thrombin forming a thrombomodulin-thrombin complex -> activates protein C / S

Question 4

Protein C / S

Answer 4

Inhibits factor V / VIII / inhibitor of tPA

Ultimately, leads to increased amounts of plasmin

Question 5

Activators of plasminogen

Answer 5

1. Thrombin

2. t-PA (activated by protein C / S)

Question 6

vWF

Answer 6

Glycoprotein

Functions:

1. Binds / keeps VIII inactive until thrombin releases it
2. Binds to collagen / forms X-links w/ plt

Question 7

Plasmin

Answer 7

Lyses fibrin / fibrinogen -> FDP, which inhibit thrombin

Thrombin + t-PA assist the conversion of plasminogen to plasmin

Plasminogen receptors on the surface of many cells esp. endothelial cells -> prevent spontaneous clot formation

Question 8

Activator of protein C / S / Z

Answer 8

Binding of thrombin to thrombomodulin in normal vessels to form a complex that activates protein C / S / Z

Question 9

FDP functions

Answer 9

1. Inhibit plt aggregation
2. Inhibit fibrin polymerisation
3. Inhibits thrombin formation

Question 10

Factors activated by thrombin

Answer 10

I (fibrinogen)

V

VIII

IX

X

XIII (X-linking of fibrin)

Question 11

Vitamin K dependent factors

Answer 11

II (prothrombin)

VII

IX

X

Question 12

Hepatic factors

Answer 12

I (fibrinogen)

II (prothrombin)

V

VII

VIII

IX

X

XI

XIII

Protein C/S