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Block 3 PATH Exam - Making of a blood clot (#18)


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What does heparan sulfate do?
Catalyzes activation of ATIII by heparin
What does vWF do?
Tethers platelets to site of vessel wall inury
What happens to thrombomodulin, heparan, PGI2, and tPA after injury?
They get stripped away or are no longer produced

This removes anti-coagulants
Allows coagulation to proceed towards healing
On what cells is tissue factor found (2)?
Cells of sub-endothelial layer
Monocytes migrating to injury
What does "flipase" do?
Flips PS (phosphotidyl serine) to outside of membranes

Makes PS available to help catalyze reactions
What is calcium's role in coag?
Catalyzes rxns. by promoting attachment of enzymes/zymogens to surface
PT monitors which pathway?
Extrinsic pathway
aPTT monitors which pathway?
Intrinsic pathway
In a LAB aPTT, what factors activate the intrinsic coag pathway?

How is this different from in the body?
Factor XII, prekallikrein, and HMWK

In the body, Factor XI initiates the intrinsic pathway

NOTE: deficiencies of FXII and its activators will prolong the aPTT
(BUT, they will NOT cause bleeding)
What does factor XIII do?
Transglutaminates fibrin, stabilzing clots
What is prolonged first in Vitamin K deficiency?

PT or aPTT

Factor VII falls first, so PT is prolonged
What is included in an aPTT assay in a lab (3)?
"Activator" -- pre-kallikrein, HMWK
What is included in a PT assay in a lab (3)?
Tissue factor

NOTE: thromboplastin = tissue factor + phospholipids
Where does the Vitamin K dependent carboxylation occur?
In the liver
What factors does thrombin feedback affect to accelerate coag?
Factors V, VIII, XI, XIII
What is EDTA?
Calcium chelator

Can be used as an anti-coagulant
What is Factor I
What is Factor II
What is Factor III
Tissue factor

Primary cell initiator of coagulation
What is Factor IV
What is Factor XIII?

What does it do?

Cross-links fibrin, stabilizing clots
How do oral contraceptives affect coagulation?
Decrease the effectiveness of anti-thrombin III

May lead to increased venous thromboembolism
How do different levels of thrombin affect Factors V and VIII?
Low levels - accelerate Factors V and VIII

High levels - breakdown Factors V and VIII
(via Protein C pathway)
What synthesizes Vitamin K-2?
Bacteria in the gut

NOTE: SO, treatment that kills gut bacteria can cause Vit K def
How does bile duct obstruction play into coagulation?
Vit K is fat-soluble

If bile duct is obstructed, Vit K absorption is compromised

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