anticoagulant, antiplatelet and thrombolytic drugs

Question 1

haemostasis

Answer 1

arrest of blood loss from a damaged vessel at the site of injury involves .. in sequence

1) vascular wall damage
2) primary haemostasis
3) activation of blood clotting

Question 2

what does vascular wall damage incur ?

Answer 2

exposes collagen and tissue factor (TF, thromboplastin)

Question 3

what does primary haemostasis incur?

Answer 3

> local vasoconstriction

>platelet adhesion, activation and aggregation by fibrinogen

Question 4

activation of blood clotting …

Answer 4

… and the formation of a stable clot (by fibrin enmeshing platelets)

Question 5

key events in primary haemostasis

Answer 5

> vessel damage exposes collagen to which platelets bind and become activated
activated platelets extend pseudopodia and synthesise and release thromboxane A2 (TXA2)
thromboxane A2 binds to: platelet GPCR thromboxane receptors TP receptors causing mediator release serotonin (5-hydroxytryptamine) and adenosine diphosphate
:vascular smooth muscle TXA2 receptors causing vasoconstriction that is augmented by mediator 5-HT binding to smooth muscle GPCR 5-HT receptors
ADP binds to platelet GPCR purine receptors that:
act locally to activate further platelets, >aggregate platelets into a ‘soft plug’ act the site of injury - via increased expression of platelet glycoprotein receptors that bind fibrinogen, thromboxane acts similarly
expose acidic phospholipids on the platelet surface that initiate coagulation of blood and solid clot formation