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IHL Exam 1 > Platelet Function (McCormick) > Flashcards

Platelet Function (McCormick) Flashcards

1
Q

Thrombopoietin

A

a cytokine produced by liver and kidney

regulates platelet production and differentiation of megakaryocytic

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2
Q

What factors can regulate the process of platelet formation

A 
any factor that is converting the common myeloid progenitor into megakaryocyte:
TBO thrombopoietin
SCF Stem cell factor
IL-3
GM-CSF
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3
Q

what is the normal concentration of platelets in peripheral blood and lifespan of these platelets

A

150,000-450,000 x 10E9/L

7-10 days

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4
Q

Where are marginalized or sequestered platelets found?

A

sinusoids in spleen and in the pulmonary vasculature

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5
Q

List the platelet components

A 
Glycoprotein R
Tubulin mts
actin/myosin proteins
alpha granules
dense-core granules
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6
Q

Function of glycoprotein R on platelet

A

external surface to bind to vWF

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7
Q

Function of tubulin mt on platelets

A

encircle disk forming inner skeleton

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8
Q

Function of actin/myosin proteins on platelets

A

contractile proteins in center- important for platelet plug

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9
Q

What are in the alpha granules of platelets

A

vWF, platelet factor IV, TGF-B1, PDGF, factors V and XIII and fibrinogen

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10
Q

What are in the dense-core granules of platelets

A

ADP, serotonin, histamine, epinephrine, and Ca2+ (procoagulants)

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11
Q

3 general steps of platelet formation

A

Adhesion
Activation
Aggregation

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12
Q

Describe the events in Adhesion of platelets

A

vWF is exposed to to injury to endothelium(via shearing, cytokines or hypoxia), the GpIb R on platelets bind to vWF

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13
Q

Describe the events in Activation of platelets

A

The binding to vWF causes G protein intracell cascade

mediated via PLC and Ca2+ influx to initiate the “release rxn of platelets”

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14
Q

What is included in the “release rxn” of platelets?

A

exocytosis of dense storage granule contents
exocytosis of alpha granule contents
production of TXA2
Thrombin will cause changes in cytoskeleton of platelets to form filpodia

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15
Q

Describe the events in Aggregation of platelets

A

Release of ADP, serotonin, TXA2 and Ca2+ activates this cascade
the binding of vWF and R activatre platelet aggregation
GpIIb/IIIa Receptors on platelet surface bind fibrinogen to make bridges

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16
Q

what is the role of thrombin in platelet formation

A

activates factor XI which will facilitate the interaction of intrinsic and extrinsic pathways

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17
Q

difference of clot and platelet

A

clot will retract to form a plug via interaction of actin and myosin in center of platelet

18
Q

define hemostasis

A

balance of blood for optimal tissue perfusion

basically the balance of procoagulants and anticoagulants in blood

19
Q

What is the bleeding time test and what can it tell you about a patient

A

cut patient, test how long it takes for bleeding to stop. normal within 8 min optimal 5 min
tells you about disorders in primary hemostasis like vWF disease

20
Q

What are platelet aggregation studies and what can they tell you about a patient

A

measure aggregation in presence of pro-aggregant

functionality of qualitative platelet disorders

21
Q

Platelet factor 4- what can this test tell you about a patient

A

measures release of PF4 from alpha granules of platelets.

detects functional or qualitative platelet disorders

22
Q

What is Von Willebrand disease

A

vWF normally is a carrier protein for factor VII and acts as an adhesive surface for platelets at vascular injury site
defects result in bleeding tendencies

23
Q

5 fundamental steps of clotting

A 
Vessel Injury: endothelial damage
Primary hemostasis: platelet function
Secondary hemostasis: coagulation-fibrin
Anti-thrombosis: clotting inhibition
Fibrinolysis: breakdown-removal of clot
24
Q

3 fundamental building blocks for a clot

A

endothelium, platelets, coagulation (fibrin formation)

25
Q

What occurs in response to endothelial injury

A

Endothelin is released to cause vasoconstriction

contact with underlying ECM causes activation of clotting and platelet adhesion

26
Q

what is vWF role in circulating blood

A

binds to factor VIII thus increasing its time circulating

27
Q

Which domain of vWF binds to ECM and which to the platelet glycoprotein R

A

A3 binds to collagen on ECM and A1 binds GP1b on filopodia

28
Q

where is fibrinogen found? role in clotting?

A

circulates in blood- forms bridge between filopodia of platelets

29
Q

Glanzmann thrombasthenia

A

when the platelets can’t grab onto eachother in clot formation. Problem with GpIIb/IIIa complex

30
Q

do patients with VW disease have lower platelet count?

A

no does not affect quantity.

31
Q

What is the drug Reopro used for?

A

blocks GpIIb/IIIa therefore blocking platelet plug formation.

32
Q

How does aspirin prevent clot formation

A

inhibits conversion of AA into TXA2 which is a stimulator of clotting

33
Q

What is the phospholipid platform and when does it form?

A

platelets when activated expose phospholipid-rich portion of membrane and this acts to accelerate fibrin production 100-1000 fold. Secondary Hemostasis

34
Q

How do we obtain serum from blood draw?

A

whole blood allowed to clot then centrifuge down and take supernatant(serum) from top (red top)

35
Q

How do we obtain plasma from blood draw?

A

blood is drawn into tube with anticoagulant that prevents clotting, then centrifuged and supernatant is plasma (blue top)

36
Q

What is a common anticoagulant for plasma samples/?

A

Sodium citrate. citrate will bind Ca2+ and prevents its coagulation activity (blue top)
purple top uses EDTA for anticoagulant

37
Q

Two types of categories to test primary hemostasis

A

quantitative platelet count(automated analyzer)

qualitative platelet function testing- aggregation studies

38
Q

What is an automated analyzer that is used in testing form problems in primary hemostasis

A

laser light scattering- measure the report Mean Platelet Volume

39
Q

Difference between appearance of young platelets vs old

A

younger platelets are larger and more functional

40
Q

how can you test for glanzmann thrombasthenia?

A

aggregation studies. no response to eli, ADP, collagen and AA or thrombin

41
Q

Tests to monitor coagulation

A

Prothrombin time

activated Partial Thromboplastin Time (aPTT)

IHL Exam 1 (11 decks)

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