Renal physiology.

The kidney is composed of one million nephrons that function as a series of integrated units. The excretion of a wide range of natural and artificial compounds results from unselective filtration and specific reclamation of wanted substances. Active transport of weak acids and weak bases supplements this mechanism. In addition to its excretory function, the kidney has important endocrine and metabolic functions and influences the function and metabolism of most body systems. An understanding of renal function affords an explanation for many of the phenomena observed in renal disease.