Haemostatsis Flashcards
What is haemostasis
- maintains flowing blood in fluid state and confined to circulatory system
What is the most important feature about haemostatic response
Localised
What happens to blood vessels when injury happens
Vasoconstriction
What is the primary response driven by
- platelets
- endothelial
- fibrinogen
What would 1ry response defects cause in
- immediate bleeding
What is the secondary response driven by
- circulating enzymes
- platelets
- fibrin (product of fibrinogen)
What would 2ry response defects cause in
- delayed bleeding
Describe the process of clot forming
- collagen exposed —> platelets adhesion
- fibrinogen secretion, ADP & TXA2
- aggregation of molecules
- thrombin formation
What does fibrinogen do in clot formation
Allows platelets to stick together
What is embolisation
- broken off clot from thrombin
- highly dangerous
Which stage of clot formation do drugs target
Secretion
What is the mechanism of platelets control
Autocrine
How come do platelets stick together quickly
- large no. of receptors
- high no. of platelets
- rich in signalling proteins
- +ve feedback
Describe 1ry response
- platelet adhesion
- shape change
- granule release (ADP, TXA2)
- recruitment
- aggregation
What are the different shapes of platelets
- flowing disc shape
- Rolling ball shape
- hemisphere (firm, reversible adhesion)
- spreading (irreversible adhesion)
What are dense granules and what do they do
- ATP, ADP, serotonin, Ca2+
- +ve feedback of platelet activation
What are a granules
- platelet factor 4
- PAI-1
- platelet derived growth factor
- chemokines
What do a granules do
- help coagulation
- ail wound healing
Give examples of stimulatory agonists
- ADP
- Adrenaline
- Collagen
- Thrombin
- Fibrinogen
Give examples of inhibitory agonists
- Adenosine
- NO
What si the overall reaction to a vascular trauma
- vasoconstriction
- platelet activation —> adhesion to collagen —> shape Change
- granule release —> platelet activator, coagulation factors, vasoconstrictors
What are the steps of coagulation
- TF exposed
- FVII binds to TF
- FVII auto-activated
- FVIIa cleaves —> activating FX
- FXa prothrombin, —> thrombin
- thrombin, fibrinogen —> fibrin
Where are TFs present
- perivascular cells
