Functional development of the kidneys in ontogenesis as main effector of water salt homeostasis system

Based on our own findings and literary data, we discuss the development of osmotic, volumetric and ion-regulating kidney functions in human ontogenesis. It has been shown that in the morning at rest on an empty stomach, the main functions of the kidneys, except for filtration and reabsorption processes, correspond to the definitive level at the age of 2-3 years. After water-salt load, which activates the corresponding systems, the volume-regulatory function of the kidneys approaches the adult level at the age of 7-8 years, and the osmo-regulatory and ion-regulatory functions approach the adult level at the age of 10-11 years. The article discusses the role of the reserve capabilities of the kidneys in stabilizing water-salt homeostasis after the ingestion of excess water and salts.