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Heme Week 3 > Platelets > Flashcards

Platelets Flashcards

1
Q

How are platelets made from megakaryocytes?

A

via endomitotic synchronous nuclear replicaron where the nucleus divides and the cytoplasm does not until the end

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2
Q

How long do platelets last?

A

7-10 days normally

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3
Q

What organ has a massive storage of platelets?

A

the spleen

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4
Q

Describe the membrane of a platelet.

A

It is intended to increase the surface area available for binding

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5
Q

Where is calcium stored in a platelet?

A

dense tubular systems (similar to the ER in other cells)

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6
Q

What else do dense tubular systems?

A

1) half of the nucleotides needed for metabolism- secreted when the platelets are activated
2) serotonin

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7
Q

What are in the larger alpha granules?

A

1) vMF
2) V and VIII
3) fibrinogen
4) PDGF mitogen
etc.

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8
Q

T or F. Platelets have nuclei

A

F.

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9
Q

Can GIIb/IIIa bind vMF?

A

yes, but fibrinogen is the main one

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10
Q

What makes calcium come out of the dense granules?

A

receptor binding that cleaves IP3 via PIP2 from the membrane. IP3 allows calcium to be released

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11
Q

What role does cAMP play in platelets?

A

elevating cAMP levels in a platelet turns it off

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12
Q

What does Factor V do once released from alpha granules?

A

binds directly to the platelet surface

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13
Q

What role does vitamin K play in coag?

A

it gamma-carboxylates residues on factors (II, VII, IX, and X) and allows those residues to bind calcium which embeds itself into the platelet surface

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14
Q

What other receptors are present on platelets?

A
  • thrombin
  • ADP
  • epinephrine/serotonin
  • TxA2
  • fibrinogen
  • vMF
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15
Q

What is the main role of TxA2 in platelets?

A

It is a major proponent of platelet aggregation because once generated (when the receptor that activated PIP2 to IP3 to release calcium, it also releases arachidonic acid and initiates that cycle) it inhibits production go cAMP from ATP

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16
Q

So how does aspirin play in?

A

blocks cyclooxygenase= no TxA2= elevated cAMP= no platelet aggregation

irreversibly

also blocks PGI2 (made from endothelial cells)- an inhibitor of platelet aggregation so its kind of offset considering you have way more endothelial cells than platelets in the body but SMALL doses (81mg) (baby aspirin) only blocks cyclooxyrgenase so it works great!

17
Q

What kind of bleeding to people without platelets have?

A
  • bruising
  • mucus membrane type bleeding (nose bleed, heavy periods)
  • petechiae
18
Q

What kind of bleeding do hemophilia patients have?

A

deep tissue and joint bleeding

19
Q

If a patient is not showing thrombocytopenia but they are bleeding, what should be suspected?

A
  • vMF disease

- qualititative platelet abnormality

20
Q

What a platelet aggregometer?

A

can put a cuvette in and keep at 37C and can stir platelet rich (slow spin) and platelet poor plasma (spin hard to bring down platelets) and can measure as a change in optical density as a function of some inhibitor/activator

if its normal, then no qualitative abnormality

21
Q

What would Glanzman Thrombasthenia (qualitative) look like on platelet aggregometer?

A

just a straight line at 100% because no platelet aggregation occurs

22
Q

What would Bernard Soulier (qualitative) look like on platelet aggregometer?

A

would look normal (risteocetin would be abnormal)

23
Q

What is a thromboelastogram (TEG)?

A

draw anti coagulated whole blood and put into machine with probe and cup (two machines- in one the cup rotates and the probe is stationary and vice-versa in the other) and add calcium and a clot forms and the instrument follows it. Takes ~30 minutes

measures resistance of probe to rotation

24
Q

What is the r time in a TEG?

A

time it takes the clot to start

25
Q

What is a good treatment for patients with a platelet antibody?

A

corticosteroids and splenectomy (where most of the platelet removal occurs)

26
Q

Can drugs induce antibodies against platelets?

A

yes, common with heparin-induced thrombocytopenia

27
Q

What are some causes of thrombophilia/cytosis?

A
  • trauma
  • iron deficiency
  • splenectomy
  • inflammatory disease
  • malignancy (Hodgkins, carcinoma)
  • MPD

ITS MIM

28
Q

What kinds of infections could cause thrombocytosis?

A

osteomyelitis

TB

29
Q

Why would a splenectomy cause a thrombocytosis?

A

because all the platelets in the spleen will be released into blood stream

Heme Week 3 (11 decks)

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