Osmosis is the tendency of a fluid, usually water, to pass through a semipermeable membrane into a solution where the solvent concentration is higher, thus equalizing the concentrations of materials on either side of the membrane. Antidiuretic hormone is also known as vasopressin. Vasopressin is a peptide hormone, synthesized in the hypothalamus and released by the posterior pituitary gland, that stimulates capillary muscles and reduces the flow of urine and increases its concentration.
