Lecture 10: Physical coagulation Flashcards
The physiologic coagulation pathway occurs via factor ____ whereas the contact pathway occurs via factor ____
Physiologic: Tissue factor -> factor VII
Contact: negatively charged surface -> factor XII
What is part 1 of the coagulation process?
- initiation complex
- VIIa in presence of TF –> X to Xa and IX —> IXa
- occurs on disrupted endothelium
What does Xa do?
-converts a small amount of prothrombin (II) to thrombin (IIa)
Once initial small amount of thrombin produced it activates _________
- cofactors needed in complexes VIII and V
- then gets shut down
What do VIIIa and IXa do?
- Go to platelet surface where they activate X to Xa
- IXa is the protease
- VIIIa is the cofactor
What is the final complex formed on the platelet suracfe once Xa produced
- Xa binds with Va to convert prothrombin (ii) to thrombin (IIa)
- Huge burst of thrombin formed (further drives process)
What are the 4 naturally occurring inhibitors of coagulation?
- Tissue Factor Pathway Inhibitor (TFPI)
- Protein C
- Protein S
- Antithrombin
Which clotting factors are inactivated by protein C?
V and VIII
Which clotting factors are inhibited by antithrombin?
Xa, IXa, XIa
What are the vitamin K dependent proteins involved in coagulation?
- Prothrombin
- VII
- IX
- X
- Protein C
- Protein S
What is the role of Vitamin K in coagulation?
- Carboxylates glutamate residues in the GLA domain
- Absence of carboxylation results in failure to bind membranes and lack of activity
Vitamin K is synthesised by ____ in the ___ and absorbed using ____
Synthesised by bacteria in the gut
Absorbed using bile
Why is vitamin K administered to newborns?
- Newborns naturally deficient
- Bleeding in brain associated with trauma of delivery
