Off the top of your head, you may think your scalp is different from the rest of your skin simply because it covers your skull and grows thicker hair. In fact, there are indeed some distinctions between the skin stretched over your cranium and the skin protecting the rest of your body.
The scalp is composed of five layers -- the outermost layer is skin. Between that layer of skin and the bone of your skull lies connective tissue, a fatty layer that joins the skin to the cranial muscles. Blood vessels and nerves run through this layer. Beneath that are layers that house cranial muscles, carry blood flow to your eyelids and allow the scalp to slide. Put your hand on the top of your head and gently push -- loose areolar tissue allows that movement [source: Harris].
Aside from the layers below the skin itself, there are two big differences between your scalp and the rest of your skin: Scalp skin is some of the thickest skin of the body, and it carries more blood than the rest of your skin [source: Draelos]. This is why head wounds bleed so much. Your scalp also contains many sebaceous glands, which produce oil, or sebum, that protects hair [source: Harris].
Because of the abundance of sebaceous glands, it's important to clean your scalp thoroughly. If oil builds up, you can end up with clogged hair follicles or dandruff. Dandruff is caused by bacteria that get trapped in the oil and produce fatty acids that cause itching and swelling. This causes the skin cells on your scalp to replenish more frequently, and flakes of dead skin can get caught in your hair and fall to your shoulders [source: Draelos]. Many skin conditions that affect the scalp can go unnoticed because of your hair, so it's important to check your scalp for moles and growths [source: Mayo Clinic]. To learn more about your scalp and scalp conditions, see the links on the following page.