The kidney has two layers: the outer layer, called the cortex, which is reddish brown and granular, and the inner zone, the medulla, which is darker and reddish brown in color. The medulla is subdivided into 6 to 18 cone-shaped sections called the pyramids. The pyramids are inverted so that each base faces the cortex and the tops project toward the center of the kidney. Separating the pyramids are bands of tissue called renal columns. A renal lobe consists of a renal pyramid and its surrounding tissue.