Question 1

Identify the platelet receptor and plasma protein required for normal platelet adhesion. Platelet receptor Plasma protein&#10;A) Glycoprotein (GP) IV Factor VIII&#10;B) Platelet factor 4 (PF4) Factor V&#10;C) GP IIb/IIIa Fibrinogen&#10;D) GP Ib/IX/V von Willebrand factor (VWF)

Accepted Answer

GP Ib/IX/V is the platelet receptor required for normal platelet adhesion, while von Willebrand factor (VWF) is the plasma protein responsible for binding to the receptor and initiating platelet adhesion. Choice A is incorrect because GP IV is not a known platelet receptor involved in adhesion, and Factor VIII is a clotting factor rather than a plasma protein involved in platelet adhesion. Choice B is incorrect because Platelet factor 4 (PF4) is not a known platelet receptor involved in adhesion, and Factor V is a clotting factor rather than a plasma protein involved in platelet adhesion. Choice C is incorrect because GP IIb/IIIa is a receptor involved in platelet aggregation rather than adhesion, and although fibrinogen can bind to this receptor, it is not the plasma protein required for initiating platelet adhesion.

Question 2

Which of the following is true of thrombopoietin?&#10;A) Another name for erythropoietin&#10;B) Promotes apoptosis of megakaryocytes&#10;C) Binds to the ligand Mpl on the membrane of platelet precursors&#10;D) Enhances platelet adhesion

Accepted Answer

Thrombopoietin is a hormone that binds to the Mpl receptor on the membrane of megakaryocyte progenitor cells to promote their differentiation into platelets. It does not have any effect on erythropoiesis or apoptosis, and does not directly enhance platelet adhesion.

Question 3

All of the following stimulate megakaryocyte and platelet production except:&#10;A) Interleukins&#10;B) Erythropoietin&#10;C) Thrombopoietin&#10;D) Megakaryocyte colony-stimulating factor (Meg-CSF)

Accepted Answer

Erythropoietin stimulates red blood cell production, not megakaryocyte and platelet production. The correct options that stimulate megakaryocyte and platelet production are A, C, and D (Interleukins, Thrombopoietin, and Meg-CSF).

Question 4

Platelet agonists are substances that:&#10;A) Bind to phospholipid in the platelet membrane&#10;B) Promote apoptosis&#10;C) Activate platelets&#10;D) Enhance megakaryocyte proliferation

Accepted Answer

Platelet agonists are substances that activate platelets, leading to platelet aggregation and blood clotting. Examples of platelet agonists include thrombin, ADP, and collagen, which all bind to specific receptors on the platelet surface, initiating a signaling cascade that ultimately results in platelet activation.

Question 5

Which of the following is true of megakaryocytes as they mature?&#10;A) Nucleus becomes polyploid&#10;B) Cytoplasmic basophilia becomes more pronounced&#10;C) Size decreases&#10;D) Nucleoli become more prominent

Accepted Answer

Megakaryocytes undergo endomitosis, meaning their nucleus replicates without cytokinesis, leading to a polyploid nucleus.

Question 6

How are platelets released into peripheral circulation from the bone marrow?&#10;A) Mature platelets squeeze between sinusoid endothelial cells.&#10;B) Megakaryocyte cytoplasmic fragments extend through the endothelial cells, lining the sinusoids, into blood and then shed platelets.&#10;C) Platelets adhere to white cells and exit with them.&#10;D) Megakaryocytes exit the marrow with white cells and then platelets fragment off once they reach the blood.

Accepted Answer

Platelets are derived from megakaryocytes which are large precursor cells found in the bone marrow. When these megakaryocytes mature, their cytoplasmic extensions, called proplatelets, extend through the endothelial cells lining the sinusoids in the bone marrow. Eventually, these proplatelets break off into small fragments, which are released into the peripheral circulation as platelets.

Question 7

From where are additional platelets first derived when the circulating count decreases?&#10;A) Bone marrow&#10;B) Stem cells&#10;C) Cells marginated on vessel endothelial cells&#10;D) The 30% of mature cells stored in the spleen

Accepted Answer

When the circulating platelet count decreases, additional platelets are first derived from the 30% of mature platelets stored in the spleen.

Question 8

When platelets are activated, all of the following occur except:&#10;A) ($\alpha$)-Granule contents are released.&#10;B) Smooth cytoplasmic membrane margins change to spiny projections.&#10;C) The prostaglandin (eicosanoid synthesis) pathway is activated.&#10;D) Adenosine diphosphate (ADP) release is inhibited.

Accepted Answer

When platelets are activated, all of the following occur except that ADP release is inhibited. Platelets release ADP when activated, which helps to promote platelet aggregation and the formation of blood clots.

Question 9

Platelet storage pool disorder is a deficiency of:&#10;A) Platelet phospholipids&#10;B) ($\alpha$)-Granules&#10;C) Platelet lysosomes&#10;D) ($\beta$)-Granules

Accepted Answer

Platelet storage pool disorder is a deficiency of (F1F1F1S1F1F1F10)-Granules.

Question 10

Phospholipids in the platelet membrane are important for all of the following functions except:&#10;A) Supply of arachidonic acid&#10;B) Receptor for plasma fibrinogen&#10;C) Receptor for plasma coagulation enzymes&#10;D) Forms part of the platelet glycocalyx

Accepted Answer

The answer of Phospholipids in the platelet membrane are important...

Question 11

Which of the following is not a function of the platelet surface-connected canalicular system (SCCS)?&#10;A) Produces energy for the cell&#10;B) Delivers granule contents to the surface&#10;C) Connects the internal contents to the surface&#10;D) Stores plasma coagulation factors

Accepted Answer

The answer of Which of the following is not a...

Question 12

What system is responsible for controlling platelet activation?&#10;A) Eicosanoid (prostaglandin) pathway&#10;B) Surface connect canalicular system&#10;C) Membrane glycoproteins&#10;D) Dense tubular system

Accepted Answer

The answer of What system is responsible for controlling platelet...

Question 13

Identify the platelet receptor and plasma protein required for normal platelet aggregation. Platelet receptor Plasma protein&#10;A) GP IIb/IIIa Fibrinogen&#10;B) GP IV Factor VIII&#10;C) GP Ib/IX/V VWF&#10;D) PF4 Factor V

Accepted Answer

The answer of Identify the platelet receptor and plasma protein...

Question 14

A platelet histogram can be generated using automated hematology analyzers, where frequency is plotted versus platelet volume. When this histogram is examined, which of the following is true?&#10;A) Distribution is gaussian.&#10;B) Mean platelet volume (MPV) is 14 fL.&#10;C) Distribution is log normal with a small population of large platelets.&#10;D) MPV is 5 fL.

Accepted Answer

The answer of A platelet histogram can be generated using...

Question 15

Which of the following is a useful marker for identification of platelet precursors?&#10;A) VWF&#10;B) PF4&#10;C) Phospholipase&#10;D) Factor V

Accepted Answer

The answer of Which of the following is a useful...

Deck 13: Platelet Production, Structure, and Function