HAEMOSTASIS Flashcards
What is haemostasis?
The balance of pro coagulant and anti coagulant activity
What are the overall steps of haemostasis? (4 steps)
- vasoconstriction
- temporary platelet plug
- coagulation
- fibrinolysis
What is primary haemostasis?
The Platelet plug
What is secondary haemostasis?
The clotting cascade
What are two important components of platelets and what do they consist of?
Alpha granules - holds factors V, VIII, VWF and fibrinogen
Dense body - ATP, ADP, Calcium
What is platelet adherence?
platelets are at site of injury - VWF is activated on platelets, exposed collagen and gp1b is present
What is platelet activation?
Releases ADP (changes platelet to spherical shape) and TXA2 (activated platelet aggregation) and exposure of gpIIbIIIa
What is platelet aggregation?
platelets express gpIIbIIIa, and fibrin which forms a platelet plug formation
What does the extrinsic pathway begin with?
Vascular damage
What tissue factors are involved with the extrinsic pathway?
FVII(a), FX(a), FII (a)
What is the importance of thrombin?
- required for intrinsic pathway
- back activation of co factors V and VIII
- activator of clotting cascade and platelets
What is the intrinsic pathway activated by?
Thrombin
What tissue factors are involved in the intrinsic pathway?
FXII, FXI, FIX (co factor VIII)
What do all pathways convert?
Fibrinogen to fibrin
What is fibrinolysis?
The breakdown of fibrin (breaks down clots)
