erythropoézis

Erythropoiesis is the process by which red blood cells, also known as erythrocytes, are produced. This essential biological process primarily occurs in the red bone marrow of adults. The development of a red blood cell is a complex, multi-stage differentiation that begins with a hematopoietic stem cell. This multipotent stem cell differentiates into a myeloid progenitor, which then commits to the erythroid lineage.

The earliest recognizable erythroid precursor is the proerythroblast. This cell undergoes several maturation stages, including basophilic erythroblast, polychromatophilic erythroblast, and orthochromatophilic erythroblast. During these stages, the cell nucleus shrinks and is eventually expelled, and the cytoplasm changes color as hemoglobin synthesis increases. The cell then becomes a reticulocyte, which is an immature red blood cell that still contains residual ribosomal RNA. After a short period in circulation, typically one to two days, the reticulocyte matures into a fully functional erythrocyte.

Erythropoiesis is tightly regulated by the hormone erythropoietin (EPO). EPO is produced mainly by the kidneys in response to low oxygen levels in the blood, a condition called hypoxia. When oxygen levels fall, the kidneys release more EPO, which then stimulates the bone marrow to increase the rate of red blood cell production. Conversely, when oxygen levels are adequate, EPO production decreases, slowing down erythropoiesis. This feedback mechanism ensures that the body maintains an appropriate number of red blood cells to carry oxygen efficiently. Nutrients such as iron, vitamin B12, and folic acid are also crucial for normal erythropoiesis.