Coagulation Flashcards
What is physiological hemostasis
Repair of everyday wear and tear, happening all the time
What is pathological hemostasis
-Clotting in the absence of hemorrhage
-Excessive clotting
-Clotting in the wrong location
What are the basic components that maintain hemostasis
Vessels
Platelets
Coagulation factors
Inhibitors
What are the steps of hemostasis
Vasoconstriction
Platelet Activation
Coagulation cascade
Antithrombotic control
Vasoconstriction -
VERY fast, neurogenic
Vessel spasm
What are platelets filled with
Alpha and dense granules
What is in alpha granules
Adhesion molecules and GFs
What is in dense granules
Activators, cofactors, some GFs
What important things live under the endothelial layer of the vessel
von Willebrand factor
collagen
Who produces vWF
Endothelial cells, platelets, megakaryocytes
Where is vWF stored
Weibel palade bodies
What does vWF bind to
Glycoprotein IIb/IIIa on the platelet
What are the steps involved in making the platelet plug
Adhesion
Shape change
Secretion
Aggregation
What happens during adhesion
Platelets bump into exposed vWF –> weak attachments
Roll along vessel wall and encounter collagen –>
Integrin forms stronger attachments
What happens during shape change
Collagen and thrombin (and platelet-activating factor and ADP) activate platelets
Platelets change shape
More stable plug is formed
What happens during secretion
Platelets dump all their granules
Platelet plug activates other platelets as they pass
What happens during aggregation
Platelets flip phosphatidyl serine to the outside of their membrane (now negatively charged)
Fibrinogen bridges form between platelets
Why is it important for the platelets membranes to have a negative charge
Helps with the coagulation cascade
What is the goal of secondary hemostasis
To have fibrin (glue) form around the platelet plug to create a good seal
Which coag factors are made in the liver
II, VII, IX, X, XII, XIII
Which coag factors need to be carboxylated
II, VII, IX, X
What are the three pathways in the coag cascade
Intrinsic
Extrinsic
Common
What molecules are involved in the extrinsic pathway
Tissue factor (III), VII
What sets off the extrinsic pathway
Trauma that exposes TF to blood
What molecules are involved in the common pathway
X, V, II (thrombin)
What molecules are involved in the intrinsic pathway
XII, XI, IX, VIII
What sets off the intrinsic pathway?
Damage to endothelial cell
What activates the common pathway
TF + VII and/or VIII
Which pathway is the main activator of the cascade
Extrinsic
Draw the coagulation cascade
What test is used to test the intrinsic pathway
aPTT
Activated partial thromboplastin time
What test is used to test the extrinsic pathway
PT
Partial thromboplastin
What test is used to test the common pathway
aPTT and PT - remember the cascade is like a Y
What factors are hemophiliacs lacking
IX and/or VIII
What factors will be impacted by a vit K deficiency
II, VII, IX, X
Why do we care about vitamin K
Coag factors need to be modified in order to be active, the enzyme that drives the redox cycle needs vit K in order to work
What does thrombin do
Cleaves fibrinogen –> fibrin
Activates platelets
Mediates vascular permeability
Activates a fibrinolysis inhibitor
What is the ultimate goal of hemostasis
To return normal blood flow following an injury
Do animals that have hypocalcemia have a hard time clotting
NO. Coag needs very little Ca. To not have enough Ca to not clot you would already be dead
Do animals lacking factors XI and XII clinically bleed
No
