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 lighter-colored outer part of the kidney is the renal cortex. The darker inner part is the renal medulla. Blood is filtered in the renal cortex and medulla to form urine. Within the kidney, urine travels through many structures before it reaches the ureter. The renal medulla contains dark triangular areas of tissue called the renal pyramids. Urine flows through a renal pyramid and exits at the renal papilla, the tip. The renal papilla has collecting ducts, small openings that allow urine to pass through.