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.
Each kidney has the following four coverings on its exterior. 1  Fibrous capsule: It surrounds the kidney and is closely applied to its outer surface. 2  Perirenal fat: It surrounds the fibrous capsule.3  Renal fascia: It is a condensation of connective tissue and lies outside the perirenal fat.hen viewed in transverse section, each kidney appears to consist of two layers. The dark brown outer layer is called cortex and the light brown inner layer is called medulla, which is composed of about one dozen renal pyramids. The layers are not discrete and there are projections form one to the other.