Primary hemostasis

Question 1

Platelet peripheral zone

Answer 1

Glycocalyx: outermost membrane contains platelet phospholipids which binds clotting factors onto the platelet surface. Site of Glycoprotein receptors

Question 2

Platelet Sol gel zone

Answer 2

platelet retraction/ contraction function & platelet shape; microtubule/ microfilaments.

Question 3

Platelet membrane zone

Answer 3

Open canicular system, dense tubular system

Question 4

Platelet organelle zone

Answer 4

Storage & platelet release function; contains granules; dense bodies, alpha granules, lysosomal granules

Question 5

What is exposed after an injured vessel?

Answer 5

Subendothelial collagen microfibrils.

Question 6

Vasoconstriction purpose

Answer 6

Slow down blood flow and divert blood away from the injured vessel

Question 7

List platelet activation stimulators

Answer 7

vWF, collagen, epinephrine, ADP, thrombin, thromboxane A2

Question 8

Platelet adhesion

Answer 8

Plts adhere to exposed collagen via receptor GPVI within vessel wall.
GPIb-IX-V complex (von Willebrand factor receptor) is activated by shear stress and ristocetin.
Note: clot is unstable and reversible

Question 9

Platelet secretion

Answer 9

Release of alpha granules and dense bodies.
Synthesis and release of thromboxane A2, which recruits more platelets to the injured vessel wall.
Note: step is irreversible and leads to the formation of the primary platelet plug

Question 10

Platelet aggregation

Answer 10

Adherence of plts to each other is mediated by receptor GPIIb/IIIa (fibrin receptor and platelet plug stabilizer). Binds fibrinogen in presence of Ca++ (ionized)

Question 11

What Plt receptor complex mediates platelet aggregation?

Answer 11

GPIIb/IIIa