The scalp is the skin and other specialized tissues covering the top of the human skull. The scalp consists of five distinct layers, which can be remembered by using the mnemonic 'S.C.A.L.P.' as follows, moving from the outside to the inside:
- Skin: contains hair follicles, sweat glands, and sebaceous glands. The small arteries that supply the skin of the scalp are encased in tough connective tissue and do not spontaneously retract and contract when they are torn. Scalp wounds are therefore typically quite bloody, and a scalp wound can be fatal even in the absence of other injury due to extreme blood loss.
- Connective tissue: a spongelike web of elastic and inelastic fibers wrappping around small fat lobules.
- Aponeurosis: a flat, broad sheet of tendon that connects the frontal bellies of the epicranius muscle (on the forehead) to the occipital bellies of the same muscle (at the back of the head). The two bellies of this muscle pull the scalp forewards and backwards.
- Loose areolar tissue: another spongy layer of collagen fibers. The voids in this layer can be filled with blood or infected fluid. It is this loose layer that allows the scalp to slide easily over the surface of the skull, and it is the layer that is divided when a person is 'scalped'.
- Periosteum: another layer of dense connective tissue. This layer is firmly attached to the underlying bone of the skull, especially so at the sutures or joints of the bones of the skull.
"Scalp" can also be used metaphorically to describe the trophy of a victory over another person. This usage is most commonly associated with the literal practice of certain Native American peoples of scalping fallen opponents, removing their scalp to keep as a trophy. Other cultures throughout history took scalps as trophies, likely starting with the Scythians around 400 BC