281b - platelet fxn

Question 1

where does thrombin generation occur? how?

Answer 1

surface of platelets

scramblase –> negative PL on outer lipid membrane –> factors and Ca assemble

Question 2

signs of platelet defects?

Answer 2

easy bruising, petechiae

mucus bleeding

Question 3

what controls proplatelet formations in MK?

Answer 3

microtubules w/ motors –> extended from BM into vessel sinuses

Question 4

platelet lifespan

Answer 4

10 days –> apoptosis

consumed earlier in normal endo fxn too

Question 5

granules

Answer 5

released when platelets activated and change shape

dense = ADP, Ca (Small molecules)

alpha = fibrinogen, vWF (proteins)

Question 5

ITP

Answer 5

immune thrombocytopenia - autoimmune disorder

abs –> GPIIb/IIIa

Question 5

what do normal endothelial cells have for antiplatelet activity?

Answer 5

NO
PGI2
ecto-ADPase (CD39) on surface

Question 5

what do platelets binds on damaged endothelium?

Answer 5

collagen via vWF - GPIb –> rolling

fibrinogen receptors - GPIIb/IIIa –> aggregation

Question 5

hereditary defects of platelet fxn?

Answer 5

bernard-soulier syndrome = GPib + very large platelets

Glanzmann thrombasthenia = GPIIbIIIa

Question 6

platelet fxn disorders - acquired

Answer 6

drugs (ASA, NASIDS)
uremia
dysporteinemia (high IgA)
myeloproliferative disorders
CV bypass -> exhuastion from abnormal surface
Abs

Question 6

hereditary defects of platelet fxn

Answer 6

bernard-soulier syndrome = GPib

Glansmann thrombasthenai = GPIIbIIIa

Question 6

phospholipase A2 fxn in platelets?

Answer 6

converts PL from membrane –> TxA2 –> platelet agonist –> aggregation

Question 6

what molecules recruit platelets?

Answer 6

ADP
TxA2
fibrinogen