The hair is one of the primary appendages of the skin. Other skin appendages include sebaceous glands, fingernails and toenails, sweat glands and mammary glands in females.
The primary ingredients in the hair shaft include dead tissue and keratin, a protein. Hair growth, however, happens mainly in the hair follicle below the epidermis, which pushes the hair out beyond the skin.
The skin has its own built-in moisturizing system via appendages known as sebaceous glands. They are a part of the unit that contains the hair follicle and hair, and produce sebum, a moisturizer for both hair and skin. During the teen years, About.com says these glands grow larger and produce more sebum; however, as a person enters his 20s, the production gradually decreases.
The fingernails and toenails are also appendages of the skin. Stem cells located underneath the fingernails allow the nails and even sometimes the fingertips to regenerate in humans. As Science News reports, fingertips only regenerate if stem cells from the fingernails are present.
According to Dictionary.com, the appendages of the skin also include the sweat glands and mammary glands. The sweat glands produce perspiration to keep the body cool. Mammary glands are responsible for lactation or milk production to feed offspring, according to Healthline Networks.