Normal haemostasis

Question 1

Haemostasis requires the interaction of 3 compartments, what are they?

Answer 1

Blood vessels, platelets and coagulation factors, they must be tightly controlled

Question 2

Name and describe the 3 haemostatic mechanisms

Answer 2

Primary haemostasis - interactions between vessels, platelets and VWF
Secondary haemostasis - pathways of coagulation to generate a fibrin strand
Fibrinolysis - biochemical system that degrades the fibrin clot

Question 3

What are the 3 layers of arteries?

Answer 3

Intima (endothelial cells), media (smooth muscle) and adventitia (collagen, fibroblasts)

Question 4

What is released following vascular injury?

Answer 4

Endothelin-1 to cause vasoconstiction

Question 5

What is VWF role following vessel injury?

Answer 5

It is stored in storage granules in endothelial cells called Weibel Palade bodies and in the alpha granules of platelets. they perform two major roles, mediating adhesion of platelets to sites of vascular injury and binds and stabilises the procoagulant protein factor 8

Question 6

In which pathway is the most factor X made? and how much more efficient is it?

Answer 6

The intrinsic pathway produces factor X 50x more efficiently, 90% of factor Xa is made intrinsically

Question 7

What coagulation factors are in each pathway?

Answer 7

Extrinsic pathway - 3 + 7 = 10
Intrinsic pathway - TENET
Common pathway - 1 x 2 x 5 = 10

Question 8

What is the prothrombin time?

Answer 8

Tests how long it takes for blood to clot, tests for deficiencies in the extrinsic and final common pathways

Question 9

What are the naturally occurring anticoagulants in the body?

Answer 9

Protein C - inactivates factor 5 + 8
Protein S - co-factor to prot
Antithrombin - inhibits activated coagulation factors 2a (thrombin =) and factor Xa