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.
The internal structure of the kidney is divided into two main areas... a light outer area called the renal cortex, and a darker inner area called the renal medulla. Within the medulla there are eight (8) or more cone-shaped sections known as renal pyramids.