Blood Coagulation Flashcards
What are the blue structures?
What are the yellow structures?
Blue: activated platelets
Yellow: Fibrin network
Describe the clotting process.
- Blood vessle contracts and restricts blood flow
- Platelets (flat–> psuedopods) aggregate at the site (Primary hemostatic plug)
- Fibrin appears and a network is formed (Secondary hemostatic plug)
Explain Platelet (Thrombocyte) Activation
1) Platelets bind to subendothelial collagen and von Willebrand Factor.
2) Structural changes cause them to release factors that recurit and activate more platelets (TxA2 and ADP)
What is thrombocytopenia and thrombocytosis?
Thrombocytopenia: too few thrombocytes leading to excessive bleeding
Thrombocytosis: too many thrombocytes leading to blockage of BV’s
Explain the Primary hemostatic plug.
Factor 2: Prothrombin activates thrombin
Factor 1: Thrombin activated fibrinogen to fibrin
Describe the Coagulation Cascade. (Intrinisic, Extrinisic and Common)
Intrinisc Pathway: Factor 11 activates Factor 9. Factor 9 activates Factor 10. (Factor 8* helps Factor 9 to activate Factor 10/*vWF binds to Factor 8 and stabalizes it.)
Extrinsic Pathway: Factor 7 activates Factor 10 (helped by Factor 3)
Common Pathway: Factor 10 activates Factor 2 (with the help of Factor 5) Factor 2 actvates Factor 1
Notes: all helpers surround Factor 10
What is Factor IV?
Calcium; used as an adhesive to the negatively charges surfaces of collagen. (Gla proteins help Ca++ binding as well)
Which factors is Vitamin K important for? What complications can warfin bring?
Factors 10, 9, 7, and 2. Warfin can inhibit these factors which disables Ca++ binding and cannot make the clot.
Platelet Count
Prothrombin Time
Partial Thromboplastin Time
Activated Clotting Time
PC: measures number of platelets in serum (Normal 150-400K cells/microliter)
PT: measures rate of clotting by extrinsic (7-10) and common pathways (Normally 10-14 secs)
PTT: measures rate of clotting by intrinsic (11-9) and common pathway (Normally 30-42 secs)
ACT: “bedside” test of entire clotting process
Thrombin activates which factors? (Amplification)
V, VII, VIII, and XI
Describe Feedback Inhibition. Include thrombomodulin/thrombin/complex/Protein C/Protein S and what they effect.
Thrombin binds to thrombomodulin which actvates Protein C which forms active complex with Protein S. This destroys Factor V and VII slowing coagulation.
What are Serpins? Which one is key? What happens in the presence of Heparin?
Serine Protease Inhibitors are naturally occurring inhibitory proteins. Antithrombin III irreversibly inactivates thrombin as well as a few other clotting factors. With heparin, Antithrombin III is enhanced 10,000X.
Describe Fibrinolysis.
The fibrin clot is no longer needed, the clot will be dissolved.
Plasminogen inserts itself into the fibrin clot. tPA (tissue plasminogen) or U-PA (urokinase) produces plasmin which then cleaves fibrin and other clotting factors.
Hypoxia activates this signal cascade.
Examples of death by clotting.
Stroke/MI/Thrombosis
Examples of death by bleeding.
Trauma/Major surgery/Hemophilia
Common Coagulation Disorders:
1) Diffuse Intravascualr Coagulation (Sepsis/severe trauma/cancer)
2) Thrombocytopenias
3) Clotting Factor Deficiencies (Hemophilia A: VII B:XI)/von Willebrand’d Disease/ Advanced liver disease/ Vit K deficiency)
4) Drug Induced Hypocoagulation (aspirin/ anti-platelet drugs/ Warfarin/ Heparin)
5) Surgery Effects (hypercoagulative effect/ also Dilutional thrombocytopenia)
