Lecture 3: The Blood Coagulation Cascade Flashcards
The process of haemostasis is divided into which three phases?
- Vasoconstriction
- Formation of a platelet plug
- Coagulation
What do platelets bind to that is exposed when damage occurs?
Collagen. Damage to endothelial cells lining the blood vessels exposes collagen.
Why are platelets classed as cellular fragments not cells?
Because they don’t contain a nucleus.
What does circulating von Willebrand factor bind to?
Collagen and the 1b receptor of the platelet.
The release of what leads to the formation of the active IIb/IIIa receptor?
ADP. It’s released from activated platelets, and leads to the association of glycoprotein IIb and IIIa to form the active IIb/IIIa receptor complex. This then binds to fibrinogen.
For coagulation to occur, a phospholipid surface is needed, what is the advantage of this?
It limits the clot to the site of injury.
Why are calcium chelating agents used in blood storage?
To prevent coagulation of blood.
What are zymogens?
Clotting factors inactively present in the plasma.
What does thrombin do?
Converts fibrinogen to fibrin.
Also catalyses activation of several factors.
Also contributes to further platelet activation.
What removes the clot by degrading the fibrin mesh?
Plasmin.
