Question

Only erythropoiesis occurs in
(a) Erythroblast
(b) Proerythroblast
(c) Myeloid tissue
(d) Haemocytoblast

Answer 1

Hint: This is the first stage out of four stages in the development of normoblast or erythroblast. These are large cells which possess basophilic, agranular cytoplasm, round nuclei and high nuclear-cytoplasmic ratios.

Correct answer:
Only erythropoiesis occurs in proerythroblast.
Proerythroblast develops from the erythroid cells and they give rise to basophilic erythroblasts. The term erythropoiesis is given to the process of production of red blood cells or erythrocytes in our body. This production includes the development from erythropoietic stem cells to mature red blood cells. When the oxygen level decreases in circulation the process of electrophoresis is stimulated. This decrease in oxygen level is detected by kidneys and then after detection it secretes the hormone erythropoietin.

Additional Information:
-An increase in erythropoiesis can be caused by the increased level of physical activity.
-The erythropoiesis that occurs outside the bone marrow, within the spleen or liver is known as extramedullary erythropoiesis. It is found in humans with certain diseases and also in some animals.
-With the fall of oxygen level in blood, more red blood cells are produced and so results in a rise of red cells count.
-The four stages of erythropoiesis are formation of basophilic normoblast or proerythroblast, from proerythroblast to polychromatic normoblast or intermediate normoblast and then formation of orthochromatic normoblast or late normoblast and finally mature red cells are produced from reticulocyte.
-Throughout life the site of erythropoiesis changes. At the foetus stage it occurs in yolk sac, after that it occurs in liver and spleen from 2-5 months gestation before shifting finally to the bone marrow after 5 months gestation.
-In children erythropoiesis occurs in the bone marrow of most bones. In adults the site for erythropoiesis is bone marrow of the vertebrae, ribs, sternum, sacrum, pelvis and proximal femur.

So, the correct answer is, 'Proerythroblast'.

Note:
-The rate of erythropoiesis is very sensitive to the amount of oxygen available or present in the arterial blood.
-In an average our body produces 2.5 billion red cells per kilogram per day.
-The production of red cells begins in the stem cells. These are having the greatest powers of self-renewal of any adult cell.