Bowman's Capsule

A kidney contains about one million nephrons, the functional units of the kidney, and each of these consist of a renal corpuscle and a renal tubule. A "renal corpuscle" is composed of tangled clusters of blood capillaries called a "glomerulus," and a thin-walled, saclike structure, called the "Bowman's capsule," which surrounds the glomerulus. The Bowman's capsule is an expansion at the closed end of a renal tubule. It is composed of two layers of cells: an inner layer that closely covers the glomerulus, and an outer layer that is continuous with the inner layer and with the wall of the renal tubule. The renal tubule leads away from the Bowman's capsule and becomes highly coiled. The coiled portion is named the "proximal convoluted tubule." Several of the distal convoluted tubules merge into the renal cortex to form a collecting duct, which in turn passes into the renal medulla, becoming larger and larger as it joins other collecting ducts, the resulting tube is called the papillary duct.