5-29 GOUELI Coag Biochem Flashcards
(21 cards)
What is a normal platelet count?
150,000 – 450,000 platelets/uL
Define hemostasis?
Physiological blood clotting in response to injury.
Define Thrombosis?
Pathologic blood clotting
Define Hemorrhage?
Pathologic bleeding
What is the overview, big picture of how hemostasis works?
1) Vasoconstriction in response to injury
2) Platelet plug (Primary Hemostasis)
3) Fibrin plug (clot) (Secondary Hemostasis)
4) Clot dissolves (Anti-coagulants / fibrinolytics)
What are the 3 fundamental mechanisms in PRIMARY HEMOSTASIS?
Adhesion – platelets adhere to exposed collagen
Aggregation
Secretion (of platelet granule contents)
What coagulation factor does vWF stablilize?
Factor VIII
What does GP Ib bind?
vWF
What does GP VI bind?
Collagen
What does GP IIa-IIIb bind?
Other platelets via vWF/fibrinogen
What is ADP’s role in platelet aggregation?
ADP released from platelet granules -> binds platelet ADP-receptors -> activates platelets -> unmasks Gp IIb-IIIa
What is Plavix?
ADP-receptor antagonist -> ↓clot formation
If you admit someone for MI, what must you put them on?
Aspirin. Otherwise it’s malpractice
What is secondary hemostasis? What are the broad steps involved?
Secondary Hemostasis is formation of the FIBRIN PLUG (clot)
2 pathways (INTRINSIC, and EXTRINSIC) converge to common path
OVERARCHING GOAL is producing fibrin!
What is the “additional substance” necessary for the extrinsic pathway?
Tissue factor
Where does Tissue Factor come from?
Not plasma
Surface protein expressed on endothelial cells exposed to cytokines
Where do the clotting factors (eg Factor VIII, Factor IX) come from?
Synthesized by liver (as zymogens)
What is the role of phospholipids in the activation of zymogens?
Surface of activated platelets kinda flip.
This surface provides an area where zymogens can be enzymatically
cleaved to form activated factors (eg Factor VIIIa)
Will a patient with Factor XII deficiency have any symptoms? Why?
No b/c that part of the pathway can be activated by many things, including thrombin
What does heparin do?
Activates ATIII
What anticoagulant does Coumadin also antagonize? What are the implications?
Protein C and S activity also decreases from Coumadin.
Thus, admin of Coumadin to patient INITALLY causes HYPERcoag!
Thus, we BRIDGE W/HEPARIN
