Week 5 - Clotting Flashcards
What are xymogens
Inactive forms of clotting factors
What is plasma?
The supernatant of anti-coagulated blood
What is serum?
The supernatant of fully clotted blood
i.e. clotting factors/fibrinogen not present
What is Virchow’s Triad for Normal Hemostasis
Normal blood flow
Normal vascular endothelium
Normal Hemostatic balance
What is hemostasis?
What does it involve?
A mechanism which ensures retention of the blood within the vascular system.
Involves:
- endothelial lining
- platelets
- clotting factors
Describe platelets.
Formed from megakaryocytes
Non-nucleated
Half-life ~ 1 week
Activated by thrombin or ADP
Outline the overview of steps to thrombosis.
Damaged endothelial layer
- -> platelets adhere
- -> platelet aggregation and enlargement of mass
- -> fibrin deposition stabilizes platelet thrombus
What is clotting?
Tissue damage leading to fibrin clot formation
What is thrombolysis?
Tissue repair and fibrin clot dissolution
Why does fibrin form clots but fibrinogen doesn’t?
Fibrin is insoluble; fibrinogen is soluble.
Thrombin and plasmin are types of …
Proteases
What converts fibrinogen to fibrin?
Thrombin
- this leads to clot formation
What converts fibrin to fibrin degradation products (soluble and cleared by liver)?
What else is formed in this process?
Plasmin
- this leads to clot dissolution
- forms D2E fragments or D-dimers
What is the significance of D2E fragments or D-dimers?
Diagnostic markers for thrombosis/thrombolytic event
What is TFPI?
What does it do?
Tissue Factor Pathway Inhibitor
- inhibits enzymes in extrinsic clotting pathway
- -> increases propagation of intrinsic pathway
