Answer: After seven months.
Explanation:
The blood carries various substances that must be transported from one part of the body to another. Red blood cells are an important component of the blood because their function is to carry oxygen to the body tissues and exchange it for carbon dioxide, which is carried and removed by the lungs.
Erythropoiesis is the process of red blood cell (erythrocyte) production. It is stimulated by a decrease in O2 in the circulation, detected by the kidneys, which then secretes the hormone erythropoietin. This hormone stimulates the proliferation and differentiation of red blood cell precursors, which triggers an increase in erythropoiesis in hematopoietic tissues and ultimately in the production of red blood cells. <u>In adults, red blood cells are formed in the red bone marrow.</u>
In early developing fetuses, erythropoiesis occurs in the mesodermal cells of the yolk sac. In the third or fourth month, erythropoiesis moves to the liver. After seven months, erythropoiesis occurs in the bone marrow.
