This chapter is about the urinary system, which plays a vital role in maintaining the internal environment by excreting nitrogenous waste products and by selectively excreting or retaining water and electrolytes. It identifies, locates, and describes the functions of the organs of the urinary system (objectives 1-3). It explains the structure and function of the nephron--the basic unit of function of the kidney (objective 5). It traces the pathway of blood through the blood vessels of the kidney, explains how glomerular filtrate is produced, and discusses the role of tubular reabsorption in urine production and the cause of change in the osmotic concentration of the glomerular filtrate of the renal tubule (objectives 4 and 6-10). It also describes the role of tubular secretion in urine formation (objective 11). It discusses the structure of the ureters, urinary bladder, and urethra, and how they function in micturition (objectives 12 and 13).

A study of the urinary system is basic to understanding how the body maintains its chemistry within very narrow limits.