What cells produce erythropoietin and what is its function?

The correct answer highlights that kidney cells are responsible for producing erythropoietin, a hormone that plays a crucial role in the regulation of erythropoiesis, the process of red blood cell (erythrocyte) production. When oxygen levels in the blood are low, the kidneys sense this decrease and respond by increasing the production and release of erythropoietin into the bloodstream. Erythropoietin then acts primarily on the bone marrow, stimulating the production of red blood cells, which in turn increases the oxygen-carrying capacity of the blood.

By understanding this process, one can appreciate the physiological importance of erythropoietin in maintaining adequate oxygen levels in the body, especially in response to conditions such as anemia or low oxygen availability at higher altitudes. This highlights the specific function of erythropoietin in promoting erythrocyte growth directly, which is key to ensuring effective oxygen transport throughout the body.