The renal cortex is the outer part of the kidney which is situated between the renal capsule and the renal medulla. In the adult, it forms a continuous smooth outer zone with a number of projections (cortical columns) that extend down between the pyramids. The renal cortex is composed mainly of the renal corpuscles and the proximal and distal convoluted tubules, except for parts of the loop of Henle which descend into the renal medulla. It also contains blood vessels and cortical collecting ducts. The renal cortex is the part of the kidney where ultrafiltration occurs.