Question

The formation for erythrocytes in foetus takes place in
A. Red bone marrow
B. Liver and spleen
C. Sarcoplasm
D. Blood plasma

Answer 1

Hint: The process in which erythrocytes (red blood cells) are produced is called erythropoiesis. In an adult body this process occurs in the bone marrow of essentially all the bones.

Complete answer: Erythropoiesis is the development of mature red blood cells from erythropoietic stem cells. In foetus this process occurs in the liver and spleen by the third or fourth month (in the first 2 months the process occurs in the mesodermal cells of the yolk sac). Then after seven months the process occurs in the bone marrow.

Additional information: Erythropoiesis comes from the Greek words 'erythro' meaning "red" and 'poiesis' meaning "to make".
1. Until a person is five years old, the bone marrow of essentially all the bones produces red blood cells.
2. Red blood cells are produced in red bone marrow of all bones. This happens upto the age 20 years.
3. Then after the age of 20 years, red blood cells are formed from membranous bones such as sternum, ribs, scapulas, vertebrae and the iliac bones.
4. Also after the age of 20, the shaft of the long bones turns yellow bone marrow due to fat deposition and is further not able to do erythropoietic function (means to produce red blood cells).

So, the correct answer is option B.

Note: In humans and some animals, red blood cells formation also occurs outside the bone marrow, within the liver or spleen. This is called extramedullary erythropoiesis.