Erythrocyte Production and Destruction

Question 1

1. Which of the following is an erythrocyte progenitor?
   a. Pronormoblast
   b. Reticulocyte
   c. CFU-E
   d. Orthochromic normoblast

Answer 1

c. CFU-E

Question 2

2. Which of the following is the most mature normoblast?
   a. Orthochromic normoblast
   b. Basophilic normoblast
   c. Pronormoblast
   d. Polychromatic normoblast

Answer 2

a. Orthochromic normoblast

Question 3

3. What erythroid precursor can be described as follows: the
   cell is of medium size compared with other normoblasts,
   with an N:C ratio of nearly 1:1. The nuclear chromatin is
   condensed and chunky throughout the nucleus. No nucleoli are seen. The cytoplasm is a muddy, blue-pink
   color.
   a. Reticulocyte
   b. Pronormoblast
   c. Orthochromic normoblast
   d. Polychromatic normoblast

Answer 3

d. Polychromatic normoblast

Question 4

4. Which of the following is not related to the effects of erythropoietin?
   a. The number of divisions of a normoblast
   b. The formation of pores in sinusoidal endothelial cells
   for marrow egress
   c. The time between mitoses of normoblasts
   d. The production of antiapoptotic molecules by erythroid
   progenitors

Answer 4

b. The formation of pores in sinusoidal endothelial cells
for marrow egress

Question 5

5. Hypoxia stimulates RBC production by:
   a. Inducing more pluripotent stem cells into the erythroid
   lineage
   b. Stimulating EPO production by the kidney
   c. Increasing the number of RBC mitoses
   d. Stimulating the production of fibronectin by macrophages of the bone marrow

Answer 5

b. Stimulating EPO production by the kidney

Question 6

6. In the bone marrow, RBC precursors are located:
   a. In the center of the hematopoietic cords
   b. Adjacent to megakaryocytes along the adventitial cell
   lining
   c. Surrounding fat cells in apoptotic islands
   d. Surrounding macrophages in erythroid islands

Answer 6

d. Surrounding macrophages in erythroid islands

Question 7

7. Which of the following determines the timing of egress of
   RBCs from the bone marrow?
   a. Maturing normoblasts slowly lose receptors for adhesive molecules that bind them to stromal cells.
   b. Stromal cells decrease production of adhesive molecules over time as RBCs mature.
   c. Endothelial cells of the venous sinus form pores at
   specified intervals of time, allowing egress of free cells.
   d. Periodic apoptosis of pronormoblasts in the marrow
   cords occurs.

Answer 7

a. Maturing normoblasts slowly lose receptors for adhesive molecules that bind them to stromal cells.

Egress : action of leaving; exiting

Question 8

8. What single feature of normal RBCs is most responsible for
   limiting their life span?
   a. Loss of mitochondria
   b. Increased flexibility of the cell membrane
   c. Reduction of hemoglobin iron
   d. Loss of the nucleus

Answer 8

d. Loss of the nucleus

Question 9

9. Intravascular or fragmentation hemolysis is the result of
   trauma to RBCs while in the circulation.
   a. True
   b. False

Answer 9

a. True

Question 10

10. Extravascular hemolysis occurs when:
    a. RBCs are mechanically ruptured
    b. RBCs extravasate from the blood vessels into the tissues
    c. Splenic macrophages ingest senescent cells
    d. Erythrocytes are trapped in blood clots outside the blood vessels

Answer 10

c. Splenic macrophages ingest senescent cells

Question 11

11. A pronormoblast in its usual location belongs to the RBC
    mass of the body, but not to the erythron.
    a. True
    b. False

Answer 11

b. False

Question 12

12. A cell has an N:C ratio of 4:1. Which of the following statements would describe it?
    a. The bulk of the cell is composed of cytoplasm.
    b. The bulk of the cell is composed of nucleus.
    c. The proportions of cytoplasm and nucleus are roughly
    equal.

Answer 12

b. The bulk of the cell is composed of nucleus.