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Hematology 2 > PLATELETS > Flashcards

PLATELETS Flashcards

(102 cards)

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1
Q

What is the primary function of platelets?

A

To help stop bleeding by forming blood clots.

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2
Q

Do platelets have a nucleus?

A

No.

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3
Q

What is the normal platelet count range in blood?

A

150 to 400 x 10⁹/L.

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4
Q

What is the average lifespan of a platelet?

A

8 to 9 days.

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5
Q

Where are platelets produced?

A

In the bone marrow.

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6
Q

Which cells produce platelets?

A

Megakaryocytes.

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7
Q

How many platelets can a single megakaryocyte produce?

A

2,000 to 4,000 platelets.

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8
Q

What happens to platelets after they are used?

A

They are removed by the spleen and liver.

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9
Q

What triggers platelet activation?

A

Exposure to damaged blood vessel surfaces or inflammatory signals.

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10
Q

Where are one-third of platelets stored in the body?

A

In the spleen.

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11
Q

Are platelet counts higher or lower in older adults?

A

Lower.

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12
Q

What happens to platelet shape when activated?

A

They become round and form extensions (pseudopods).

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13
Q

What dye is used to identify nucleic acid in reticulated platelets?

A

Thiazole orange.

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14
Q

What type of platelets are produced quickly in response to bleeding?

A

Reticulated (stress) platelets.

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15
Q

What’s the average size of a normal platelet (in diameter)?

A

2.5 µm.

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16
Q

What are megakaryocytes?

A

Large bone marrow cells that make platelets.

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17
Q

What is the size of a megakaryocyte?

A

30 to 50 µm in diameter.

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18
Q

Do megakaryocytes have a single or multilobed nucleus?

A

Multilobed.

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19
Q

What does TPO stand for?

A

Thrombopoietin.

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20
Q

What is the main function of thrombopoietin?

A

Stimulates megakaryocyte development and platelet production.

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21
Q

Where is thrombopoietin mainly produced?

A

Liver.

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22
Q

What kind of mitosis do megakaryocytes undergo?

A

Endomitosis.

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23
Q

What is endomitosis?

A

A process where DNA duplicates without cell division.

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24
Q

What is the result of endomitosis?

A

Polyploid megakaryocytes (multiple copies of chromosomes).

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25
What is the maximum ploidy sometimes reached in disease states?
128N.
26
What are the three stages of megakaryocyte maturation?
MK-I (megakaryoblast), MK-II (promegakaryocyte), MK-III (mature megakaryocyte).
27
Which stage does the demarcation membrane system (DMS) start to appear?
MK-I.
28
What does the demarcation membrane system do?
Divides cytoplasm into future platelets.
29
Which transcription factor promotes megakaryocyte development?
GATA-1.
30
Which factor suppresses megakaryocyte development?
MYB.
31
What does RUNX1 regulate in megakaryocytes?
Switch from mitosis to endomitosis.
32
What is the earliest identifiable megakaryocyte precursor?
MK-I (megakaryoblast).
33
Which stage shows full lobulated nuclei and DMS spread?
MK-III.
34
What is the role of FOG1?
Cofactor that helps GATA-1 regulate megakaryocyte development.
35
How many megakaryocytes does a healthy person have?
About 10⁸.
36
How many types of granules are in platelets?
Three: α-granules, dense granules, lysosomes.
37
Which granules contain clotting factors?
α-granules.
38
Which granules contain calcium and serotonin?
Dense granules.
39
What do lysosomes in platelets do?
Break down waste and damaged material.
40
How many α-granules are in one platelet?
50 to 80.
41
What color do dense granules stain in electron microscopy?
Black.
42
What receptor appears on α-granules and SCCS during activation?
P-selectin.
43
Which protein helps platelets stick to collagen?
GP Ia/IIa (α2β1).
44
What is the main adhesive protein released during vessel injury?
Von Willebrand Factor (VWF).
45
What receptor binds to VWF on platelets?
GP Ib/IX/V.
46
What are two agonists stored in dense granules?
ADP and serotonin.
47
Which granule releases fibrinogen and VWF?
α-granules.
48
Which granule appears latest during megakaryocyte development?
Dense granules.
49
What enzyme do platelet lysosomes contain?
Acid phosphatase.
50
What structure transports granule contents to the surface?
SCCS (Surface-Connected Canalicular System).
51
What maintains platelet shape at rest?
Microtubules.
52
What cytoskeletal protein contracts during activation?
Actin.
53
What happens to membrane phospholipids during activation?
Phosphatidylserine flips to the outer layer.
54
What is the function of the Dense Tubular System (DTS)?
Stores calcium and supports activation enzymes.
55
What receptors do thrombin bind to?
PAR1 and PAR4.
56
What type of receptor is PAR1?
A seven-transmembrane receptor (STR).
57
What is the role of IP3 in platelet activation?
Releases calcium from DTS.
58
What does DAG activate?
Protein kinase C.
59
What pathway produces TXA2 (thromboxane A2)?
Eicosanoid (cyclooxygenase) pathway.
60
What does TXA2 do?
Promotes vasoconstriction and platelet aggregation.
61
Which G-protein is involved in IP3-DAG pathway?
Gq.
62
What is pleckstrin?
A protein that regulates actin contraction.
63
What enzyme cleaves arachidonic acid from phospholipids?
Phospholipase A2.
64
What does ADP bind to on platelets?
P2Y1 and P2Y12 receptors.
65
What is the function of P2Y12 receptor?
Promotes sustained platelet aggregation.
66
What does prostacyclin (PGI2) do?
Inhibits platelet activation.
67
Which organ produces prostacyclin?
Endothelial cells.
68
What is the effect of increased cAMP in platelets?
Inhibits activation.
69
What do platelet microparticles do?
Promote coagulation and inflammation.
70
What triggers microparticle formation?
High intracellular calcium.
71
What is immune thrombocytopenic purpura (ITP)?
A condition where the immune system destroys platelets.
72
What is a synthetic TPO mimetic?
A drug that mimics thrombopoietin.
73
Name one TPO mimetic.
Romiplostim (NPlate).
74
What is eltrombopag used for?
To treat low platelet counts in ITP or hepatitis C.
75
Which interleukin helps megakaryocytes mature?
IL-11.
76
What growth factor supports early megakaryocyte differentiation?
IL-3.
77
Which condition results from too many platelets?
Thrombocytosis.
78
What is thrombocytopenia?
A low platelet count.
79
What can cause thrombocytopenia?
Hypersplenism, bone marrow disease, or immune destruction.
80
What is the danger of excessive platelet activation?
Blood clots (thrombosis).
81
What does aspirin do to platelets?
Inhibits TXA2 production, reducing activation.
82
What type of clot forms mostly from platelets and VWF?
White clot.
83
What is a red clot composed of?
Fibrin and red blood cells.
84
Where do white clots commonly form?
Arteries.
85
Where do red clots commonly form?
Veins.
86
Which factor helps megakaryocyte switch to endomitosis?
RUNX1.
87
Which cells help guide megakaryocyte development in bone marrow?
Stromal cells.
88
What is a proplatelet?
A long extension from a megakaryocyte that sheds platelets.
89
What blood vessel structure do proplatelets pierce?
Sinusoidal endothelium.
90
What test is used to detect megakaryocyte markers?
Flow cytometry.
91
Which marker disappears as megakaryocyte matures?
CD34.
92
Which glycoprotein supports platelet-platelet binding?
GPIIb/IIIa (αIIbβ3).
93
Which protein stabilizes factor VIII in plasma?
VWF.
94
What is the effect of ADAMTS13?
Cuts large VWF into smaller pieces.
95
What shape do platelets take on Wright-stained films?
Lavender, irregular or circular.
96
What is a syncytium in platelet aggregation?
A mass of fused platelets.
97
What structure makes up the glycocalyx?
Carbohydrates on the platelet surface.
98
What does the platelet cytoskeleton control?
Shape change and secretion.
99
Which filaments help maintain shape in resting platelets?
Microtubules and intermediate filaments.
100
What proteins form intermediate filaments?
Desmin and vimentin.
101
What is the predominant in the outer blood plasma layer?
Neutral phospholipis
102
What is the predominant in the inner, cytoplasmic layer?
Polar phospholipids

Hematology 2 (3 decks)

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