The substance of the kidney is made up of an outer cortex and an inner medulla. A portion of each nephron may be located in both cortex and medulla, but the renal corpuscles are only present in the cortex. The cortex can be divided into an outer zone and inner zone based on the distribution of the corpuscles. The medullary rays are groups of straight collecting tubules and loops of Henle in the cortex. Between the medullary rays are cortical labyrinths, composed of renal corpuscles and convoluted tubules.