Deck 13: Platelet Production, Structure, and Function

Question 1

From where are additional platelets first derived when the circulating count decreases?

A)bone marrow
B)stem cells
C)cells marginated on vessel endothelial cells
D)spleen

Answer 1

spleen

Question 2

Platelet agonists are substances that

A)bind to phospholipid in the platelet membrane.
B)promote apoptosis.
C)activate platelets.
D)enhance megakaryocyte proliferation.

Answer 2

activate platelets.

Question 3

How are platelets released into peripheral circulation from the bone marrow?

A)Mature platelets squeeze between sinusoid endothelial cells.
B)Megakaryocyte cytoplasmic fragments extend through the endothelial cells, lining the sinusoids, into blood and then shed platelets.
C)Platelets adhere to white cells and exit with them.
D)Megakaryocytes exit the marrow with white cells, and then platelets fragment off once they reach the blood.

Answer 3

Megakaryocyte cytoplasmic fragments extend through the endothelial cells, lining the sinusoids, into blood and then shed platelets.

Question 4

How many circulating platelets are produced from a single megakaryocyte?

A)200-400
B)2000-4000
C)6000-8000
D)10,000-12,000

Question 5

What system is the "control center" for platelet activation?

A)eicosanoid (prostaglandin) pathway
B)surface connect canalicular system
C)membrane glycoproteins
D)dense tubular system

Question 6

Which of the following is the liver-secreted plasma enzyme that digests "unused VWF"?

A)ADP
B)TXA2
C)ADAMTS-13
D)GPIb

Question 7

Which of the following is not a function of the platelet surface-connected canalicular system (SCCS)?

A)produces energy for the cell
B)delivers granule contents to the surface
C)connects the internal contents to the surface
D)stores hemostatic proteins

Question 8

Which of the following is true of megakaryocytes as they mature?

A)nucleus becomes polyploid
B)cytoplasmic basophilia becomes more pronounced
C)size decreases
D)nucleoli become more prominent

Question 9

Identify the platelet receptor and plasma protein required for normal platelet aggregation.
Platelet receptorPlasma protein

A)GP IIb/IIIa fibrinogen
B)GP IV factor VIII
C)GP Ib/IX/V VWF
D)PF4 factor V

Question 10

Phospholipids in the platelet membrane are important for all of the following functions except

A)supply of arachidonic acid.
B)receptor for plasma fibrinogen.
C)receptor for plasma coagulation enzymes.
D)forms part of the platelet glycocalyx.

Question 11

A platelet histogram can be generated using automated hematology analyzers,where frequency is plotted versus platelet volume.When a platelet histogram from a normal patient is examined,which of the following is true?

A)Distribution is gaussian.
B)Mean platelet volume (MPV) is 14 fL.
C)Distribution is log normal with a small population of large platelets.
D)MPV is 5 fL.

Question 12

Which of the following substances is stored in dense granules?

A)serotonin
B)platelet factor 4
C)fibronectin
D)protein C inhibitor

Question 13

Identify the platelet receptor and plasma protein required for normal platelet adhesion.
Platelet receptorPlasma protein

A)glycoprotein (GP) IV factor VIII
B)platelet factor 4 (PF4) factor V
C)gp IIb/IIIa fibrinogen
D)gp Ib/IX/V von Willebrand factor (VWF)

Question 14

Which of the following accurately describes reticulated (stress)platelets?

A)They appear in compensation for thrombocytopenia.
B)They are smaller than mature circulating platelets.
C)Their diameter exceeds 6 µm.
D)Both a and c are true.

Question 15

Which of the following megakaryocyte membrane markers disappears as differentiation proceeds?

A)CD34
B)CD41
C)CD42
D)CD61