Final answer:
The kidneys release erythropoietin (EPO) in response to low blood oxygen levels, signaling the bone marrow to produce more erythrocytes (red blood cells, or RBCs), which are essential for transporting oxygen throughout the body.
Step-by-step explanation:
The cells in the kidneys can sense blood oxygen content and release erythropoietin (EPO) when blood oxygen falls below normal levels; cells with receptors for erythropoietin are located in the bone marrow. EPO is a glycoprotein hormone secreted by the interstitial fibroblast cells of the kidneys in response to low oxygen levels, stimulating the production of erythrocytes (red blood cells, or RBCs). The primary role of erythrocytes is to transport oxygen throughout the body, and when their numbers are insufficient due to reduced oxygen in the blood, the kidneys produce more EPO to signal the bone marrow to produce additional erythrocytes, thereby restoring oxygen levels and maintaining homeostasis.