A projecting ridge or fin on the bottom of the hull of a boat or ship that improves directional control and is often weighted for added stability. 2. The principal structural member of an aircraft, resembling a ship's keel in shape and function.
The outer, reddish region, next to the capsule, is the renal cortex. This surrounds a darker reddish-brown region called the renal medulla. The renal medulla consists of a series of renal pyramids, which appear striated because they contain straight tubular structures and blood vessels.
By Mayo Clinic Staff. Kidney pain â also called renal pain â refers to pain from disease or injury to a kidney. You might feel kidney pain or discomfort as a dull, one-sided ache in your upper abdomen, side or back. But pain in these areas is often unrelated to your kidneys. Your kidneys are situated in the back of your abdomen under your lower ribs, one on each side of your spine.