Scalp hair follicles. Historical artwork of sect- ioned human scalp showing two hair follicles. Hair (brown) comprises dead cells containing keratin, a fibrous protein. The root of each hair is embedded in a follicle (pink). The root is surrounded by a bulb (globular, brown), which contains living tissue and supplies the hair with keratin. Hair is formed when new cells produced in the root push up older cells, which then become keratinised. Sebaceous glands (brown lobes, either side of hair) secrete sebum through small ducts leading into the follicles. An arrector pili muscle (pink, diagonal) supports each hair. Taken from a book by Swiss physiologist von Kolliker (1817-1905).