Overall structure of the mammalian skin with hair follicle. Hypodermis, dermis, and epidermis constitute the skin. The epidermis is a specialized epithelium, mostly composed of keratinocytes at different stages of differentiation (see text). The dermis, located below the epidermis, consists of a fibrous scaffold composed of ECM, fibroblasts, and immune cells. The dermis hosts blood vessels, nerves, and hair follicles. The bulge, located in the outer root sheath of the hair follicle, houses stem cells which constantly replenish the hair follicle with new cells (keratinocytes, melanocytes), and replenish the sebaceous gland and the epidermis after injuries.