title: Renal physiology series: Part 3 of 8. Urinary concentration and dilution.
abstract: The maintenance of extracellular volume depends on the appropriate excretion of both salt and water. When extracellular volume is expanded, the excretion of a dilute urine facilitates the return of extracellular volume to normal. When extracellular volume is contracted, the retention of both salt and water and the excretion of a small amount of concentrated urine contributes to the reexpansion of extracellular volume. The formation of either a dilute or concentrated urine is dependent on the physical arrangement of the loops of Henle, collecting tubules, and vasa recta within the kidney medulla, the transport properties of each segment; and the appropriate presence or absence of antidiuretic hormone (ADH), a hormone synthesized in the hypothalamus and secreted from the posterior pituitary gland.
authors.forename: P
authors.initials: P
authors.lastname: Preisig
mesh_terms: D006801:Humans; D007684:Kidney Tubules / Q000033:anatomy & histology / Q000502:physiology*; D009994:Osmolar Concentration; D014556:Urine / Q000737:chemistry / Q000502:physiology*; D014667:Vasopressins / Q000502:physiology
chemical_list: D014667:Vasopressins