Platelet Function

Question 1

What are the 3 steps for the formation of a platelet plug?

Answer 1

1. Platelet Adhesion
2. Platelet Activation
3. Platelet Aggregation

Question 2

Describe the process of platelet adhesion.

Answer 2

endothelial damage–release of:
PGI2, tpA, vWF, thromboplastin (tissue factor)
vWF binds exposed collagen.
platelets bind vWF via Gp1b receptor

Question 3

Describe the process of platelet activation?

Answer 3

after platelets adhere, they change conformation and form pseudopods that help them bind tightly to site of injury
secrete substances: fibrinogen, thrombin, thromboxane A2, ADP, PDGF, serotonin, lysosomal enzymes, vWF

Question 4

Describe the process of platelet aggregation.

Answer 4

released ADP from platelets that are activated is attached to platelet receptor. Then Gp2b3a receptor pops up on platelet. This binds the fibrinogen that was released.
A bunch of platelets start aggregating by binding fibrinogen

Question 5

vWF is linked by _____ bonds. IT is released from 2 things and has 2 functions and increases 2 lab values. What are they?

Answer 5

disulfide bonds

• *Endothelial cells (weibel palade bodies)
• *platelets alpha granules
• **stabilizes Factor 8
• *causes platelet adhesion
• *increases PTT
• *increases bleeding time IF DEFICIENCY

Question 6

Describe the contents of the 2 types of granules of platelets.

Answer 6

dense granules: ADP, Ca++ (important for coag)

alpha granules: vWF, fibrinogen

Question 7

What is the MOA of aspirin?

Answer 7

irreversibly inhibits COX1,2
decreases thromboxane A2 production
No effect on PT or PTT
but b/c it is anti-platelet, increases bleeding time

Question 8

What are the SE of aspirin?

Answer 8

gastric ulcers (COX1)
Reye syndrome in kids w/ viral infections: hepatoencephalopathy. Don't give to kids except Kawasaki
tinnitus
respiratory alkalosis via hyperventilation-->metabolic acidosis
interstitial nephritis

Question 9

What are the ADP receptor inhibitors?

Answer 9

clopidogrel
ticlodipine
ticagrelor
prasugrel

Question 10

What are the GP2b3a inhibitors?

Answer 10

Abciximab: monoclonal antibody fab fragment
eptiFIBatide
tiroFIBan

Question 11

What would you use to treat a STEMI? NSTEMI? If PCI was unavailable.

Answer 11

NSTEMI: anti-platelet therapy like GP2b3a inhibitor
STEMI: tpa

Question 12

What’s the deal with cilostazol and dipyridamole?

Answer 12

phosphodiesterase III inhibitors, increase cAMP in platelets to prevent aggregation