Blood Coagulation Cascade and Reg Factors Flashcards
Define hemostasis
Prevent blood loss
- Damage? Stop bleeding
- Normal conditions? Maintain fluidity
Define thrombosis
Form a clot or thrombus inside an intact blood vessel
Hemostasis and thrombosis involved what components?
Vascular endothelium
Platelets
Coag system
Fibrinolytic system
Coagulation cascade has what pathways involved?
Extrinsic
Intrinsic
Common
Vitamin K depedent factors are?
2, 7, 9 and 10
Contact activated factors are?
12, prekallikrien, high molecular weight kininogen
Thrombin sensitive factor
1, 5, 8, 11, 13
Hematostasis events
Localized vascular spasms
Primary hemostasis (loose plug)
Secondary hemostasis
Clot dissolution
Localized Vasoconstriction
Mediated by reflex neurogenic mechanisms –> increase Ca within SMC
Primary Hemostasis
Platelet adhesion
Platelet activation
Platelet aggregation
Form primary platelet plug
Platelet Adhesion
via von Willebrand Factor binds to GPIb (bridge between platelet and collagen)
Platelet Activation
release TxA2 which leads to platelet aggregation and activating vasoconstrictors
Platelet Aggregation
TxA2, PAF, ADP call other platelets to aggregate via fibrinogen
Secondary Hemostasis
Extrinsic Pathway (rapid response via initial coag) Inhibited by TFPI but the thrombin activates the intrinsic pathway
Intrinsic pathway does what?
Activates Thrombin-sensitive factors 5, 8 and 11 which boost thrombin production
- Promotes platelet activation
- Converts fibrinogen into fibrin
- Activated Factor 8
What does Thrombin do?
Promotes platelet activation and aggregation via proteases activated receptors
Catalyze fibrinogen to fibrin
Activates factor 8 which stabilizes platelet aggregation
OVERALL Secondary hemostatis is to do what?
Stabilize the initial soft clot
Takes longer than primary
Platelet Function
CONTAIN ONLY COX1
Bind exposed collagen
Increased Ca and PKC activation = more platelets
TxA2 stimulates new platelets and more aggregation
Dense granules are?
ADP and ATP, ionized calcium
Released first
Alpha granules are?
von Willebrand factor
Fibrinogen
Factor V and VIII
ADP does what?
Activates P2Y1 which activate phospholipase C –> increase Ca
P2Y12 inhibits adenylyl cyclase –> bind fibrogen
Pro-coagulant Properties
Promote adhension (VWF)
Anti-fibronlytic
Release of tissue factors (trigger entrinsic)
Anticoagulant properties are?
Inhibit activation and aggregation (ADP, NO)
Release anticoagulants (TFPI)
Fibrinolytic properties
Extrinsic Pathway MOA?
TF forms complex with VII which activates X which creates thrombin
Intrinsic Pathway MOA?
Form HMWK, PK and Factor XII
XII –> XI –> IX + VIII (tenase) + Ca –> X
Common Pathway
X + V = prothrombinase complex –> prothrombin –> thrombin
Thrombin: fibrinogen –> fibrin & Factor XIII –> crosslinking
PAR1 and PAR4 activation leads to
platelet activation
Pro-Thrombin effects are?
Activated PAR 1 and PAR4 Factor V, VIII, XI Fibrinogen to fibrin Factor XIII Activation of TAFI
Anti-Thrombin effects are?
Activated Protein C
APC degrades factor Va/Viii
Mutation in Factor V does what?
Prevents breakdown via APC –> thrombophilia
Antithrombin
Targets intrinsic pathway factors (X and II)
Heparin increases catalytic activity
TFPI
Inhibits Factor X which inhibits vWF –> No more X
Tissue Plasminogen Activator
Cleaves fibrin from plasmin and degrades fibrin
Vitamin K
Required to activate Factors II, VII, IX, X + protein S/C
Calcium and phospholipids required for
Tenase (VIII + IX) and prothrombinase complexes
aka clotting
Blood test for extrinsic pathway?
Prothrombin time
Blood test for intrinsic pathway?
Activated partial Thromboplastin Time
Prothrombin Time Test
Blood sample + calcium chelator
TF + phospholipids are added
Finally calcium to initiate the test
Range is 12-14 seconds (>20 = deficiency)
Activated Partial Thromboplastin TIme
Negative phospholipids + particulate is added to citrated plasma
Add Ca and test is initiated
Clot formation time is measured
Range is 26-33 sec
If you have prolonged aPTT and PT you have a defect in?
Common coagulation pathway
Hemophilia A
Fact VIII deficent
Hemophilia B
Fact IX
Hemophilia C
Fact XI