IHL I - Platelet Function

Question 0

what two events occur during endothelial injury?

Answer 0

endothelin release and contact with ECM

Question 1

endothelin

Answer 1

causes vasoconstriction

result of endothelial injury

Question 2

vWF

Answer 2

synthesized by endothelial cells

-forms a matrix on the basolateral surface that is exposed during damage

Question 3

sources of vWF

Answer 3

endothelial cells (basolateral surface)

megakaryocytes produce vWF in circulating blood
-complexed to factor VIII

platelet alpha granules

Question 4

what is vWF bound to in circulation

Answer 4

factor VIII

-increases the half life of factor 8

Question 5

A3 domain

Answer 5

binds to the collagen of the ECM

domain of vWF

Question 6

A1 domain

Answer 6

portion of vWF

binds to the platelet receptor (GPIb) on filopodia

Question 7

GPIb

Answer 7

receptor on platelets for vWF

Question 8

sequence of primary hemostasis

Answer 8

adhesion, activation, aggregation

Question 9

Gp IIb/IIIa

Answer 9

binds platelets to eachother

via fibrinogen

Question 10

fibrinogen

Answer 10

allows platelets to bond to one another

-bind to Gp IIb/IIIa receptors

Question 11

von willebrand disease

Answer 11

cannot produce vWF
-platelets cannot bind to injury site

factor VIII also has a decreased life time***
-inhibition of coagulation cascade

Question 12

glanzmann thrombasthenia

Answer 12

inability to form the GpIIb/IIIa receptors

cannot bind platelets together

Question 13

what to look for on labs for coagulation?

Answer 13

platelet count (quantitative) and activity (qualitative)

Question 14

what happens when platelet plug is formed?

Answer 14

the clot contracts down to the wall

forms a platform for secondary hemostasis
-needs to be smooth (don’t want thrombi breaking off)

Question 15

abciximab

Answer 15

used in patient to prevent micro thrombi

block GpIIb/IIIa receptor
-induces glanzmann thrombasthenia

Question 16

what is the mechanism of aspirin?

Answer 16

blocks cyclooxygenase activity

TxA2 prostaglandin reduction

Question 17

factor XIII

Answer 17

tissue factor

starts phosholipid platform that causes the coagulation to occur

Question 18

serum

Answer 18

blood is allowed to clot then centrifuged

Question 19

plasma

Answer 19

anticoagulant present that prevents clotting

blood is centrifuged and fluid supernatant collected

Question 20

anticoagulation to prepare plasma?

Answer 20

chelator of Ca2+

ex/ sodium citrate

Question 21

guantitative test?

Answer 21

platelet count (automated analyzer)

Question 22

qualitative test?

Answer 22

aggregation studies

looks at activity of platelets

Question 23

bleeding time?

Answer 23

excellent test for overall deficits in vWF

time for standardized skin incision to bleeding

less than 8 minutes (less than 5 optimal)

**tests for von willebrand disease and disorders of primary hemostatis

**ineffective in detecting disorders of secondary hemostasis

Question 24

normal range of platelets?

Answer 24

150-450 x 10"9 /L

Question 25

mean platelet volume

Answer 25

indicated through automated analyzer that tells size of platelet **young platelets are larger increase in platelet production results in an increase in MPV

Question 26

lab tests in glanzmann thrombasthenia

Answer 26

platelet count normal aggregation studies has no response to epinephrine, ADP, collagen, arachidonic acid, or thrombin

Question 27

tests for secondary hemostasis problems?

Answer 27

prothrombin time (PT) and activated partial thromboplastin time (aPTT)

Question 28

prothrombin time

Answer 28

tests in the extrinsic pathway and to monitor anticoagulant patients

Question 29

aPTT

Answer 29

used in the intrinsic pathway monitor can also be used to monitor heparin