Lecture Topic 9: Haemostasis II

Haemostasis and Blood Groups

What are the 3 responses to vessel injury?

Vasoconstriction / platelet adhesion / blood coagulation cascade

What exposure causes platelet adhesion?

Collagen exposure

What happens when a platelet is activated?

Shape change, granule secretion and activation of glycoproteins (GPIIb/IIIa)

What happens to the platelets after platelet adhesion?

Platelet activation 

What important factor is activated, to allow platelets to stick?

Glycoproteins 

Give an example for a potent platelet aggregator?

Thromboxane A2

What is a platelet aggregator?

When the platelets stick to each other

What is the difference between platelet adhesion and platelet aggregator?

Adhesion is sticking to damaged vessel wall, Aggregator is sticking to other platelets

How does ADP help platelet aggregation?

It makes the platelets swell 

What are the 2 granules secreted from platelet activation to help with aggregation?

Thromboxane A2 / ADP 

What is released from platelet activation to aid vasoconstriction?

Serotonin / thromboxane A2 / ADP 

What initiates blood coagulation cascade? (the extrinsic pathway)

Tissue factor (factor III) combining with factor VII

Why is the intrinsic pathway needed, on top of the extrinsic pathway during coagulation?

Because the extrinsic pathway can be stopped/inhibited

What are all the clotting factors involved in the intrinsic pathway of coagulation?

Factor XII , XI , IX and FVIII (as a co-factor for IXa)

What is the importance of the intrinsic pathway of coagulation?

Provides amplification for clot formation 

What does the prothrombin activator consist of?

Factor Xa + Factor Va

What does prothrombin activator do?

Convert prothrombin to thrombin (IIa)

What does the TF-VIIa complex do in coagulation?

Activates factor X to FXa 

What does blood coagulation cascade allow the body to do?

Convert soluble plasma protein fibrinogen to insoluble rigid polymer fibrin

What does platelet activation release, that aids blood coagulation cascade?

Platelet phospholipid

Is the stable haemostatic plug reversible or irreversible?

Irreversible

Why must blood flow be slowed when there is a vessel injury?

Allowing platelet adhesion and clot formation to begin

How does a blood vessel carry out vasoconstriction?

Smooth muscle contraction

When factor VII is activated, how is it written?

Factor VIIa

What is the diameter of platelets?

2-3 um

Do platelets have a nucleus?

No.

What is the cell that produced platelets?

Megakaryocyte

What is the production of platelets controlled by? and what type of feedback is it?

No. of circulating platelets / negative feedback

What hormone is needed for platelet production?

Thrombopoietin / TPO

What does thrombopoietin do?

Increase platelet numbers 

What is the normal lifespan of a platelet?

7-10 days

Give an example of an ionic clotting factor

Ca 2+

What type of reactions converts fibrinogen to fibrin?

Polymerisation 

What is the enzyme that catalyses the polymerisation of fibrinogen to fibrin? (flagged)

Thrombin

What stabilises fibrin?

Factor XIII

Why is vitamin K needed for blood clotting?

Vit K produce certain clotting factors in the liver (prothrombin)

What does antithrombin do?

Inhibit thrombin (among other factors) 

What are the 2 natural ‘anti-coagulants’?

Antithrombin / Heparin

What does heparin do?

Co-factor that accelerates action of antithrombin

Where is heparin released by?

By basophils and mast cells

What is the word for the breakdown of a clot?

Fibrinolysis

What is fibrinolysis?

Breakdown of a clot 

What enzyme is involved in fibrinolysis?

Plasmin

How is plasminogen utilised in fibrinolysis?

Plasminogen is converted to the enzyme plasmin

What is the product in fibrinolysis?

Fibrin degradation products

If D antigen is present, would would your blood group be?

Rh +

If D antigen is absent, would would your blood group be?

Rh -