IHL I - Platelet Function (DSA)

Question 0

what stimulates the formation of platelets?

Answer 0

TPO and IL-3

Question 1

megakaryocytes

Answer 1

release platelets in the bone marrow

stimulated by TPO and IL-3

several thousands/day

lifespan 7-10 days

Question 2

what stimulates the production of megakaryocyte

Answer 2

SCF, TPO, IL-3, and GM-CSF

stimulate the common myeloid progenitor to form the megakaryocyte

Question 3

thrombopoietin

Answer 3

stimulation of platelet formation

-produced by liver and kidney

Question 4

what is the receptor for thrombopoietin

Answer 4

MPL receptor

located on platelets

binding to platelets destroys the TPO (negative feedback)
-more platelets, less megakaryocyte maturation

Question 5

normal blood concentration of platelets

Answer 5

150-450 x10~9/L

Question 6

thrombocytopenia

Answer 6

decrease of platelets in the blood

Question 7

thrombocytosis

Answer 7

high platelet levels in the blood

Question 8

structure of platelets?

Answer 8

external surface of glycoprotein receptors
tubulin microtubules encircle the disk forming inner skeleton
actin and myosin contractile proteins in the interior
alpha-granules
-vWF, platelet factor 4, TGF-beta1, PDGF, factors 5 and 7, and fibrinogen
dense-core granules:
-ADP, serotonin, histamine, epinephrine, and Ca2+

Question 9

what are in the alpha granules of platelets?

Answer 9

vWF, platelet factor 4, TFG-B1, PDGF, factors 5 and 8, fibrinogen

Question 10

what is in dense-core granules

Answer 10

ADP, serotonin, histamine, epinephrine, Ca2+

Question 11

where are platelets found?

Answer 11

bone marrow (production)
blood (permanent residents)

Question 12

circulating platelets

Answer 12

in the circulating blood

activated???

Question 13

sequestered platelets

Answer 13

aka marginalized

in pulmonary venous and splenic sinusoids

reserve for platelets and can increase up to 50%

Question 14

three process of platelet plug formation

Answer 14

adhesion, activation, aggregation

Question 15

mechanism of platelet adhesion?

Answer 15

binding of platelets to vWF on the endothelium exposed
-normally prevented due to negative charge on platelets and endothelial cells
initiated by increased shearing force
also promoted by release of vWF from alpha granules

Question 16

mechanism of platelet activation?

Answer 16

binding of vWF triggers G-protein signal transduction via activation of phospholipase C and Ca2+ influx

initiates release reaction:

- exocytosis of dense granules and alpha granules
- production of thromboxane A2
- thrombin causes platelet to form filolpod extensions

Question 17

mechanism of platelet aggregation?

Answer 17

release of ADP, serotonin, thromboxane A2 and Ca2+ activates additional platelets to adhere

promotes platelet aggregation

vWF binds to glycoprotein receptors and activates more platelets while forming bridges between them

Question 18

additional stuff during aggregation?

Answer 18

activation also changes the Gp IIb/IIIa receptors on the surface and allows them to bind fibrinogen
-allows platelets to form bridges between other platelets via fibrinogen

-results in platelet plug

Question 19

what promotes clot formation?

Answer 19

release of calcium from activated platelets