Haemostasis

Question 1

1. vasodilation -
2. Platelets are activated -
3. Platelets change shape -

Answer 1

caused by damage.

adhesion and aggulation take place and glycoproteins on platelets recognize collagen fibres exposed by the wound.

granules released – ADP and 5-HT.
 5-HT enhances vasoconstriction as well as thromboxane A2
 ADP and thromboxane A2 enhance activation of platelets

Question 2

4. Coagulation -

Answer 2

 INITIATION – extrinsic pathway, faster, less product. Tissue factor released. Clotting Factor VII binds to tissue factor (forms a complex) this binds to Factor X = FXa (activated).
 INTRINSIC PATHWAY – slower but more FXa. Factor IX and co-factor VIII activate Factor X = FXa.
 COMMON PATHWAY – prothrombinase activates prothrombin = thrombin. Thrombin enzyme converts fibrogen to fibrin. Need Ca2+ and vitamin K (clotting factors).