The Bowman’s capsule is an expansion at the closed end of a renal tubule. A kidney’s 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 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.