Haemostasis Flashcards
1
Q
Define haemostasis
A
- the arrest of bleeding and the maintenance of vascular patency
2
Q
What are the components of haemostasis?
A
- formation of a platelet plug
- formation of a fibrin clot
- fibrinolysis
- anticoagulant defences
3
Q
Where do platelets arise from?
A
- they are formed from budding of cytoplasm from the megakarytocyte in the bone marrow
4
Q
What is the lifespan of a platelet?
A
- 7-10days
5
Q
What causes platelet formation?
A
- endothelial damage
- expression of collagen and von willebrand factors
- platelet glycoproteins stick (platelet adhesion)
- release of other chemicals causing more recruitment (platelet aggregation)
6
Q
causes of failures of a platelet plug?
A
- vascular loss of collagen
- thrombocytopenia
- von willerband reduced function
7
Q
Define platelet adhesion?
A
- platelet glycoproteins bin to the receptors
8
Q
define platelet aggregation
A
- release of other chemicals causing more platelet recruitment
9
Q
What are consequences of platelet failure?
A
- spontaneous bruising and purpura
- mucosal bleeding
- haemorrhage
10
Q
How can primary haemostasis be investigated?
A
- platelet count
11
Q
Primary vs secondary haemostasis?
A
- primary = platelet formation
- secondary = fibrin coat
12
Q
How is a fibrin clot formed?
A
- TF/ VIIa and VIII/IXa form V/Xa
- prothrombin converted to thrombin
- fibrinogen to fibrin
13
Q
Where are clotting factors made?
A
- in the liver
14
Q
Define fibrinolysis?
A
- once bleeding is controlled, the clot is broken down
- releasing fibrin degradation products
15
Q
What is the reaction of fibrinolysis?
A
- plasminogen -> plasmin which causes fibrin to breakdoqn
