Haemostasis - 2

Question 1

What do platelets provide for coagulation?

Answer 1

Phospholipids

Question 2

What converts fibrinogen to fibrin?

Answer 2

Thrombin

Question 3

What is the main source of coagulation factors?

Answer 3

Liver mainly

Endothelium and megakaryocytes - vWF

Question 4

What coagulation factors must bind to Ca2+ to achieve full functional activity permit attachment to activated platelet surfaces?

Answer 4

Factors II, VII, IX and X

Two coagulation inhibitors - Protein C and S

Question 5

What is needed to add Ca2+ binding sites to 6 coagulation factors and inhibitors?

Answer 5

Vitamin K

Question 6

What provides the structural strength for the haemostatic plug and anchors the plug to adjacent tissues?

Answer 6

Fibrin

Question 7

Name the three main inhibitors of blood coagulation.

Answer 7

Antithrombin
Protein Ca
Protein S

Question 8

What is the key message about haemostasis?

Answer 8

Blood coagulation is a balance

Need activation and anticoagulants

Question 9

What does activation of blood coagulation and anticoagulatants do?

Answer 9

Activation - triggers coagulation
Anticoagulants are needed to stop coagulation. The right amounts of coagulants and anticoagulants are needed for effective haemostasis.

Question 10

What happens if there is too little coagulation?

Answer 10

Bleeding risk

Question 11

What happens if there is too little anticoagulation or too much coagulation?

Answer 11

Thrombosis risk (clotting inside blood vessels)

Question 12

What is fibrinolysis?

Answer 12

Clears fibrin from normal blood vessels

Question 13

Name the activators of fibrinolysis.

Answer 13

tPA

Urokinase

Question 14

Name the inhibitors of fibrinolysis

Answer 14

Plasminogen Activator Inhibitor (PAI)

Antiplasmin

Question 15

Describe how clot lysis occurs.

Answer 15

Both plasminogen and tPA can bind to fibrin.
If large amounts of tPA are present, when a clot is forming the tPA will also bind to fibrin and activate plasminogen.
Clot lysis will occur

Question 16

Where is the most important place for fibrinolysis to occur?

Answer 16

In veins

Question 17

Why is fibrinolysis not as important in arteries than in veins?

Answer 17

Fast blood flow carries activating coagulation factors (and fibrinolytic) factors away from the site of platelet activation

Question 18

Describe the normal blood flow and platelet relationships.

Answer 18

Platelets are normally unable to adhere to the smooth surface of the endothelium.
Endothelial ADPase clears ADP from activated platelets.
NO secreted
PGI2 produced

Question 19

What is the function of NO?

Answer 19

Dilates vessels, inhibits platelet activation

Question 20

What is the function of PGI2?

Answer 20

Dilates blood vessels, inhibits platelet activation

Question 21

What inhibits platelet activation?

Answer 21

NO

PGI2

Question 22

Describe the normal velocity of blood flow and the results of it.

Answer 22

Velocity of flow is faster in the centre of blood vessels due to shear stress at the endothelial cell surface.
This results in a central red cell rich zone
Plasma and platelet rich zone is adjacent to the endothelium.

Question 23

What happens in injury to the endothelium?

Answer 23

P-selectin is expressed: platelets may adhere

Endothelin produced by adjacent endothelium - produces vasoconstriction.