Haemostasis

Question 1

What two substances stop things sticking to the endothelial surface?

Answer 1

Prostacyclin

Nitric oxide

Question 2

What is the physiological factor that makes platelets bind to the right point of the injured endothelium?

Answer 2

Tissue factor

Question 3

What three things bind to the glycoprotein part of a platelet?

Answer 3

Glycoproteins are binding sites for collagen, fibrinogen and von Willebrand factor

Question 4

What receptors does a platelet have for things to bind and become activated?

Answer 4

ADP/ATP
Epinephrine
Thrombin

Question 5

What are a platelet’s three roles in haemostasis?

Answer 5

Adhere
Activation
Aggregation

Question 6

What chemical allows platelets to aggregate together?

Answer 6

Thromboxane

Question 7

What enzyme allows platelets to coagulate?

Answer 7

Scramblase activated by pathways and flips platelet membrane round so phospholipids are on surface to activate coagulation factors

Question 8

What is the role of von willebrand factor?

Answer 8

VWF is a big sticky molecule needed at sites of damage
Lack thereof results in VW disease
Sticks to collagen, platelets
Brings factor 8 into site

Question 9

What is the role of fibrinogen in forming a clot?

Answer 9

Fibrinogen binds to platelets but gets cleaved when activated to make a fibrin clot

Question 10

What are the clotting agents?

Answer 10

Factors 8-12
Prothrombin
Fibrinogen

Question 11

What are the intrinsic and extrinsic coagulation pathways?

Answer 11

Intrinsic-Tissue factor binds to factor seven which binds to other things, then prothrombin turns to thrombin, fibrinogen to fibrin. This happens quick and only produces first couple of fibrin
Extrinsic- uses factor eight to produce more fibrin

Question 12

What are natural anticoagulants and how do they each work?

Answer 12

Tissue factor pathway inhibitor-binds to activated factors ten and seven and switches them off
Activated protein C and protein S pathway- binds to activated factors five and eight and switches them off
Anti Thrombin- binds to activated factor ten and thrombin

Question 13

What is fibrinolysis?

Answer 13

Endothelium produces activators of plasminogen (tpa and upa) which activate plasminogen
Tpa cleaves plasminogen (protease) to plasmin, which attacks the clot and fragments it
Produces fibrin degradation products (used in D dimer), if present then know clot is present

Question 14

What mechanism do antiplatelet drugs affect?

Answer 14

Clopidogrel, Prasugrel and Ticagrelor affect ADP pathway

Aspirin affects cyclic oxidase pathway

Question 15

What mechanism does warfarin affect?

Answer 15

Warfarin affects factors 2, 7, 9 and 10

Prevents post translational modification of these factors so they don’t become active

Question 16

What mechanism does heparin affect?

Answer 16

Heparins bind to thrombin and get anti thrombins to kill off thrombin

Question 17

What are thrombus and thromboembolism?

Answer 17

Thrombus-Clot arising in the wrong place

Thromboembolism-Movement of clot along a vessel

Question 18

What are the three aspects of Virchow’s triad?

Answer 18

Stasis
Hypercoagulability
Vessel damage

Question 19

What are arterial thrombi?

Answer 19

‘White clot’~platelets and fibrin
Results in ischaemia and infarction
Principally secondary to atherosclerosis

Question 20

What are venous thrombi?

Answer 20

‘Red thrombus’~fibrin and red cells
Results in back pressure
Principally due to stasis and hypercoagulability

Question 21

What is heritable thrombophilia?

Answer 21

An inherited predisposition to venous thrombosis