noun, plural: renal medullae or renal medullas
The inner region of the kidney that is arranged into renal pyramids, and consists of loop of Henle, collecting tubules , vasa rectae, venulae rectae, and medullary capillary plexus
The kidney is the excretory organ responsible chiefly for filtering blood and producing urine. In vertebrates, the kidneys are paired and bean-shaped. They are located at the back of the abdominal cavity, in the retroperitoneal space. They lie on the left and the right sides of the vertebral column. In humans, the left and the right kidneys are asymmetrical. The left kidney is relatively higher and slightly bigger than the right kidney. As for the gross anatomy, the kidney has two major regions, namely the renal cortex and the renal medulla.
The renal medulla is the inner region of the kidney as opposed to the renal cortex, which is the outer region. The renal medulla is comprised of smaller conical sections of tissues called renal pyramids. In humans, there are about ten to 18 renal pyramids in the renal medulla. The loop of Henle, the collecting tubules, vasa rectae, venulae rectae, and the medullary capillary plexus are found in the renal medulla.
While the renal cortex is involved in urine dilation the renal medulla is involved in urine concentration.