haemostasis Flashcards
what are the 4 stages of haemostasis
1) primary haemostatsis - platelet plug
2) secondary haemostasis - fibrin clot
3) fibrinolysis
4) anticoag defences
what cell produces platelets
megakaryocytes
life span of a platelet
7-10 days
what is exposed in endothelial damage
collagen and von willebrand factor
what causes platelet aggregation
release of thromboxane A2 and ADP
casues of primary haemostasis failure
vascular - old or vit deficiency eg scurvy (vit c)
platetelts - thrombocytopenia or reduced function eg aspirin
vw factor - vw syndrome
clinical symptoms seen in primary haemostasis failure
bleeding and purpura
mucosa bleed- eg epistaxis , conjunctival
intercranial haemorrhage
what factor is prothrombin
factor II
what does vitamin K carboxylase
2,7,9,10
proetin s and c
what sits on the phospholipid (plateelt plug) to give it a positive charge
Calcium
what charge do clotting factors have
negative charge
what are the 3 stages of secondary haemostasis
initiation
propagation
amplification
what does tissue factor bind to and then what does this activate
binds to factor VII
activates factor V and Xa complex
what activates factors XIII abd IXa
thrombin
what test is used to measure factor XIII and IXa
activated partial thromboplastin time
causes of secondary haemostasis failure
haemophilia - single clotting factor deficiency
DIC - multiple factor deficicency
increased fibrinolysis eg complex coagulopathy
what is the presentation of haemophilia
weight bearing joint bleeds
describe fibrinolysis
tpa converts plasminogen into plasmin
plasmin converts fibrin into FDP’s (d-dimers)
describe the 4th stage of haemostasis
anti thrombin turns off thrombin and all clotting factors
give examples of naturally occurring anti-coagulations
anti-thrombin and protein c and s
what turns on protein C and S
thrombin
defects in the anti-coag stage causes what
thrombophilia
