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► Med - Year 1 > Platelet Structure and Function > Flashcards

Platelet Structure and Function Flashcards

1
Q

Primary hemostasis

A

Platelets-adhesion, activation, aggregation (AAA)

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2
Q

Secondary hemostasis

A

Coagulation cascase-3D network of fibrin, platelets, and RBCs to form fibrin clot

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3
Q

Clot removal, vessel wall restored

A

Fibrinolysis

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4
Q

Platelets form by fragmentation at the end of cytoplasmic processes extending from these cells

A

Megakaryocytes

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5
Q

Where are platelets produced?

A

In bone marrow

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6
Q

Normal platelet life span

A

10 days

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7
Q

At any one time, 1/3 of platelets are resting in this organ

A

Spleen (also a little in liver)

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8
Q

Normal platelet count

A

145,000-450,000 / ul

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9
Q

Like RBC, platelets do not contain?

Unlike RBCs, platelets contain?

A

no nucleus, mitochondria in cytoplasm

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10
Q

How and where are old platelets removed?

A

In spleen and by kupffer cells in the liver

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11
Q

Platelets contain many important glycoprotein surface receptors. List the 4 important ones:

A
  1. VWF receptor
  2. Thrombin receptor
  3. Fibrinogen receptor
  4. ADP receptor
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12
Q

GP1b/IX/V

A

Von Willebrand receptor

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13
Q

This ligand facilitates adhesion, the “glue” between platelets and subendothelium

A

Von Willebrand Factor

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14
Q

G-coupled protein platelet receptor

A

ADP receptor

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15
Q

ligand responsible for initial platelet shape change, binds ADP receptor

A

P2Y1

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16
Q

ligand responsible for completion of platelet aggregation, binds ADP receptor

A

P2Y12

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17
Q

Activates platelets through a family of unique protease-activated receptors (PAR)

A

Thrombin, binds to thrombin receptor

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18
Q

When does Thromboxane A2 (TxA2) synthesis occur?

A

platelet activation. promotes aggregation

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19
Q

In addition to glycogen stores, the central area of platelet cytoskeleton contains what two types of granules?

A

Dense and alpha granules

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20
Q

Platelet cytoskeleton contains what type of tubular system?

A

Dense. Contain microtubules (maintain shape) and actin filaments (maintain shape and platelet contraction)

21
Q

Platelet cytoskeleton contains what type of canalicular system?

A

Open, vesicles continuous with outer plasma membrane

22
Q

Main function of platelets (3)

A

Blood clotting, repair blood vessels, prevent blood loss

23
Q

In addition to serving as a cofactor in platelet adhesion, VWF is also a carrier for what?

A

Factor VIII, has other functions

24
Q

What type of granule ca you not see under conventional light microscopy (requires EM)

A

Dense granules

25
Q

Specific receptor exposure, glycoprotein IIb/IIIa, occurs during this phase

A

Activation

26
Q

What are glycoprotein IIb/IIIa’s primary ligands?

A

Von Willebrand factor and fibrinogen

This receptor is present on platelet surface but inaccessible to ligands, needs to be activated.

27
Q

ADP, ATP, serotonin, and calcium are in this granule

A

Dense granules

28
Q

Growth factors, proteoglycans, coagulation proteins, adhesive glycoproteins, and P-selectin are in this granule

A

Alpha granules

29
Q

Can see these granules under conventional light microscopy

A

Alpha granules

30
Q

Platelet shape change occurs during this phase

A

Activation

31
Q

Granule release occurs during this phase

A

Activation

32
Q

TxA2 synthesis occurs during this phase

A

Activation

33
Q

Phospholipid exposure occurs during this phase

A

Activation

34
Q

What do Phosphatidylserine and Phosphatidylethanolamine provide during phospholipid exposure?

A

The negative charge for a catalytic surface for fibrin clot formation

35
Q

These activating complexes require calcium ions for binding of coagulation factors

A

Tenase and prothrombinase complexes

36
Q

TxA2 is involved in activating other platelets. What pathway produces TxA2? What initiates the pathway?

A

The arachidonic acid pathway produces TxA2. Platelet activation initiates the arachidonic acid pathway.

37
Q

COX inhibitors

A

Inhibit TxA2 formation, an example is aspirin. This is why older people take baby aspirin to decrease risk of stroke. Essentially keep platelets quiet

38
Q

Formation of platelet cluster

A

Aggregation

39
Q

What is the glue during aggregation?

A

Fibrinogen

40
Q

What is the role of thrombin in platelet pro-coagulant activity?

A

Recruits additional activated platelets to clot and stimulates conversion of fibrinogen to fibrin (helps stabilize fibrin clot)

41
Q

How do platelets promote vessel repair?

A

Release growth factors

42
Q

These two growth factors play a major role in connective tissue repair and regeneration.

A

PDGF (platelet derived growth factor)

TGF-beta (transforming growth factor)

43
Q

Thrombocytopenia

A

Decreased platelet count (bleeding)

44
Q

Thrombocytosis

A

Increased platelet count

45
Q

What is the thrombocytosis paradox?

A

Increased platelet count usually implies clotting, but sometimes thrombocytosis is due to bleeding. If you have disfunctional platelets, they either don’t adhere, activate, aggregate etc. properly. This is an example of mixed quantitative and qualitative.

46
Q

In a platelet aggregation test, epinephrine, ADP, Collagen, Arachidonic Acid, and Ristocetin are all examples

A

Agonists (platelets are exposed to these ligands, and if they aggregate, ere is an increase in light transmission)

47
Q

During platelet aggregation test, you can see a biphasic pattern. What are the primary and secondary wave due to?

A

Primary wave: activation of GPIIb/IIIa integrin

Secondary wave: platelet granule release

48
Q

What is TxA2 involved in?

A

activating other platelets

► Med - Year 1 (48 decks)

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