Platelet plug formation Flashcards
Steps in platelet plug formation
- Exposure
- Adhesion
- Activation
- Aggregation
Which molecule binds the subendothelial collagen that is exposed after endothelial damage?
von Willebrand’s factor binds to the subendothelial collagen and attaches to activated platelets
Via which molecule does von Willebrand’s factor attach to platelets?
vWF binds to glycoprotein Ib, found on the platelet surface membrane
Source of vWF
Weibel-Palade bodies of endothelial cells and α-granules of platelets
What event causes expression of glycoprotein IIa/IIIb on the platelet membrane?
Upon adenosine diphosphate activation of the platelet, glycoprotein IIa/IIIb is inserted into the surface membrane
How do platelets adhere to one another?
Glycoprotein IIb/IIIa binds fibrinogen, bridging platelets together
Which contributors to thrombogenesis are found within platelets?
von Willebrand’s factor, fibrinogen, and, upon cyclooxygenase activation of the arachidonic acid cascade, thromboxane A2
What is the difference between the function of glycoprotein Ib and glycoprotein IIb/IIIa on the platelet surface?
- Glycoprotein Ib binds vWF on a damaged endothelial surface
- Glycoprotein IIa/IIIb binds fibrinogen attached to other platelets
What process occurs during the adhesion stage of platelet plug formation?
The platelet adheres to exposed subendothelial collagen via glycoprotein Ib and von Willebrand’s factor
Which molecule favors aggregation of platelets? Which molecules inhibit aggregation?
Thromboxane, which is released by platelets, is proaggregation; prostacyclin and nitric oxide, released by endothelial cells, are antiaggregation
What occurs during the swelling stage of platelet plug formation?
The platelet plug swells as many platelets bind together secondary to adenosine diphosphate activation of glycoprotein IIa/IIIb bridge formation
Which ion helps to strengthen the platelet plug once it has formed?
Calcium
Which stage of platelet plug formation is affected by ticlopidine and clopidogrel?
Swelling; these drugs inhibit the adenosine diphosphate-induced expression of glycoprotein IIa/IIIb
Which medication directly interferes with glycoprotein IIa/IIIb?
Abciximab
