Stages of erythropoiesis with diagram

Haematopoiesis describes the production of cells that circulate in the bloodstream. Specifically, erythropoiesis is the process by which red blood cells (erythrocytes) are produced.

On average, the body produces an astounding 2.5 billion red cells/kg/day. Erythrocytes arise from a complex line of cells, and their rate of production is tightly regulated to ensure adequate but not excessive numbers of red blood cells are produced.

In this article, we will consider the stages and regulation of erythropoiesis, and review what happens when it goes wrong.

Sites of Erythropoiesis

The site of erythropoiesis changes throughout life.

In the very early foetus, it occurs in the yolk sac. From 2 – 5 months gestation, it occurs in the liver and spleen before finally establishing in the bone marrow from about 5 months gestation.

In children, erythropoiesis can occur in the bone marrow of most bones.

However, in adults, it only occurs in the bone marrow of the vertebrae, ribs, sternum, sacrum, pelvis and proximal femur.

When erythropoiesis is inadequate

erythropoiesis takes place in