The mammalian urinary system including the basic functional unit of the nephron.

(a) The human urinary system in a woman. In the male, the urethra passes through the penis. (b) Enlarged view of a section through a kidney, showing the locations of the major internal structures and a single nephron (grossly enlarged; at the scale of this illustration, nephrons would be microscopic). (c) Structure of a nephron. The nephron begins at Bowman's capsule and terminates at a collecting duct. Many nephrons empty into a given collecting duct. Surrounding the nephron are capillaries called peritubular capillaries in the cortex and the vasa recta capillaries in the medulla.