Deck 9: The Platelet

Question 1

The normal reference interval for the mean platelet volume (MPV) is:

A) 9-11 g/dl
B) 11-14 g/dL
C) 150-450 × 10⁹/L
D) 6.8-10.2 fL

Answer 1

6.8-10.2 fL

Question 2

Which of the following criteria describes giant platelets?

A) 8-12 fL in volume
B) >5 mcM in size
C) >2N in chromosome number
D) >400 × 10⁹/L in number

Answer 2

>5 mcM in size

Question 3

Describe megakaryocyte development and the role of endomitosis and thrombopoietin in this process.

Answer 3

Platelets develop from megakaryocytes. Megakaryocyte maturation is produced through endomitosis. Endomitosis differs from mitosis in that it is missing telophase. As a result, nuclear duplication occurs without nuclear or cytoplasmic division. The resulting maturing cells are larger than in the previous stage. MK1 is smaller than MK2, which is smaller than MK3, which is smaller than MK4. The stages are very large (can reach up to 150 mcM [µm]), and can be easily spotted under low power when examining bone marrow specimens. These respond to changes in thrombopoietin. Thrombopoietin interacts with c-MPL receptor on the megakaryocytes to induce thrombopoiesis and speed up the maturation time of the megakaryocyte. Mature platelets bud off the megakaryocyte and enter the circulation.

Question 4

Platelets play a major role in forming the primary hemostatic plug by all of the following actions except:

A) Adhesion
B) Activation
C) Secretion
D) Lysis

Question 5

During what stage of megakaryocyte development are the platelets released into the circulation?

A) Between stages III and IV
B) At the end of stage II
C) During the cycling phase
D) At the point of proplatelet formation

Question 6

Explain how platelets contribute to :
a. The innate immune response
b. The adaptive immune response

Question 7

Which of the following cells is defined as cytoplasmic extensions that are released in groups and fragmented into individual platelets?

A) Megakaryocyte
B) Megakaryoblast
C) Thrombocyte
D) Proplatelet

Question 8

Nuclear replication without cytoplasmic division is defined as:

A) Asynchrony
B) Dysmyelopoiesis
C) Hematopoiesis
D) Endomitosis

Question 9

What is the typical concentration of platelets in the blood?

A) 200-600 10⁸/L
B) 150-440 10⁸/L
C) 150-450 10⁹/L
D) 250-500 10⁹/L

Question 10

The effect of thrombopoietin (TPO) on megakaryocytic cells can be described by all of the following except:

A) Promote endomitosis
B) Inhibit proliferation
C) Increase the number in the bone marrow
D) Advance the rate of maturation

Question 11

Platelets are derived from which of the following?

A) Monoblasts
B) Pronormoblasts
C) Lymphoblasts
D) Megakaryocytes

Question 12

Which of the following represents a normal platelet number and morphology?

A) A platelet that is 10 mcM in size with a blood concentration of 200 10⁹/L
B) A platelet that is 80 mcM in size with a blood concentration of 8 10⁹/L
C) A platelet that is 2.5 mcM in size with a blood concentration of 250 10⁹/L
D) A platelet that is 5 mcM in size with a blood concentration of 600 10⁹/L

Question 13

On average, how long does a platelet live in the peripheral circulation?

A) 6 hours
B) 120 days
C) 5 days
D) 10 days

Question 14

Laboratory results for a patient indicate that the platelet count is 89 × 10⁹/L. What is likely to be observed in the peripheral blood for this patient if the platelet count is the result of increased physiological platelet destruction?

A) Megakaryocytes
B) Megakaryoblasts
C) Reticulated platelets
D) Megathrombocytes

Question 15

Increased DNA content in exact multiples that are contained within a single nuclear envelope defines cells that are:

A) Polyploid
B) Proliferating
C) Apoptotic
D) Differentiated

Question 16

Which of the following describes how platelet clumping artificially alters platelet parameters?

A) Increases both the PDW and the MPV
B) Decreases both the PDW and the MPV
C) Increases the PDW and decreases the MPV
D) Decreases the PDW and increases the MPV

Question 17

Which of the following cytokines stimulate progenitor megakaryocytes to proliferate?

A) IL-6 and IL-11
B) TPO and GM-CSF
C) EPO and M-CSF
D) IL-4 and IL-10

Question 18

Identify the major cytokines that regulate platelet production and describe their effects on megakaryocytic cells and circulating platelets.