L04: Haemostasis Flashcards
What are platelets involved in
Clotting blood cells
What are the 3 types of granules in platelets
Alpha
Dense
Glycogen
What do alpha granules contain and release
F5
F8
Fibrinogen
VWF
What do dense granules contain
ADP
Serotonin
What do glycogen granules contain
Energy source for platelets
What is the first reaction of the blood vessels when there is damage
Vasoconstriction
What does vasoconstriction do to the blood flow
Decrease it
What happens to VWF
Binds to exposed collagen in the damaged vessel
When VWF binds to collagen where else does it bind to
GP1B receptors on the platelet
What happens to the GP1B platelet when VWF binds
It upregulates to GP2B receptors
When there are GP2B receptors what binds to it
More VWF
Or fibrinogen
What does GP2B cause
Cross linking of many platelets together
How are the granules in the platelet become activated to release their substances when the platelet it activated
ADP from damaged blood vessels cause degranulation of the granules
Which granules are degranulated
Dense
Alpha
When the platelets have stuck to the damaged blood vessel what is the next thing that occurs
Coagulation cascade
How many pathways does the coagulation cascade involve
3
What are the pathways of the coagulation cascade
Intrinsic
Extrinsic
Common pathway
What is the outcome of the extrinsic and intrinsic pathway
To give F10a that is in the common pathway
What happens in the extrinsic pathway
1) Factor 7 is converted to F7A by F3 (tissue factor)
2) Factor 7A converts F10 to F10A
What happens in the intrinsic pathway
1) factor 12 is converted to F12A when it touches the platelet
2) F12A converts F11 to F11A
3) F11A converts F9 to F9A
4) F9A reacts with F8 and calcium to convert F10 to F10A
What happens in the common pathway
1) F10a reacts with F5 to convert prothrombin to thrombin
2) thrombin converts fibrinogen to fibrin
Is fibrin insoluble are soluble
Insoluble
What is Bernard soulier syndrome due to
Deficiency in GP1B receptor
What is glanzmann’s thrombasthenia due to
Deficiency of GP2B receptor
What is haemophilia A due to
Deficiency in F8
What is haemophilia B due to
Deficiency in F9
What is con willebran disease due to
Deficiency of VWF
What are the 3 ways of breaking down a clot
Fibrinolysis i.e with thrombin
Protein c/s system
Antithrombin
Describe fibrinolysis
1) thrombin releases TPA
2) TPA binds to fibrin in the clot
3) circulating plasminogen binds to TPA
4) plasminogen is converted to plasmin
5) plasmin degrade the clot by breaking down the fibrin
Describe the protein C/S system
1) thrombin binds to thrombomodulin on the vessel endothelial cells
2) Protein c then binds to thrombin which is on the thrombomodulin
3) protein c becomes activated
4) activated protein c binds to protein s
5) protein c/s inactivates active F8,5 (Intrinsic pathway)
5) coagulation pathway stops
Describe the antithrombin
Anti thrombin inactivates activate F11,10,9
What test do we use to look at the function of the coagulation cascade
Coagualtion test
What does the coagulation test involve
PT
APTT
What does the coagulation test measure
Time in the intrinsic and extrinsic pathway
What pathway does the PT test look at
Extrinsic pathway
What pathway does the APTT look at
Intrinsic pathway
Usually which test is not longer
PT
Why is the PT test not long i.e the extrinsic pathway
It involves less factors so is quicker
What does a prolonged PT suggest
Deficiency in the factors involved in the extrinsic pathway :
F7
What does a prolonged APTT indicate
Deficiency in the factors involved in the intrinsic pathway: F12 F11 F9 F8
What does prolonged both PT and APTT indicate
Deficiency in the common pathway:
F5
F10
Fibrinogen
