Author Question: Which of the following is true of megakaryocytes as they mature? a. Nucleus becomes polyploid ... (Read 54 times)

BRWH · **on:** Jun 25, 2018

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 2

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. The 30 of mature cells stored in the spleen

deja · **Reply #1 on:** Jun 25, 2018

Answer to Question 1

ANS: A
As the megakaryocyte matures, it undergoes endomitosis. Deoxyribonucleic acid (DNA) synthesis normally proceeds to 8N, 16N, or 32N, but no cell division occurs. The nucleus is thus polyploid. Basophilia in the cytoplasm diminishes, but the cytoplasmic volume increases along with the nuclear size so that the cell becomes the largest cell in the bone marrow. The chromatin gradually clumps, and nucleoli become less prominent and eventually cannot be detected.

Answer to Question 2

ANS: D
When the circulating platelet count decreases, platelets are first derived from those sequestered or stored in the spleen (normally one third of those available).