The integumentary system is made up of the epidermis and its appendages (hair follicles, sweat glands, sebaceous glands, nails, and mammary glands). The epidermis and dermis are the two primary layers of skin, with a subcutaneous fascia termed the hypodermis deep within the dermis. The epidermis is made up of four to five layers of cells, the majority of which are keratinocytes, as well as three additional, less numerous cells. The epidermis is supported by the dermis. The hypodermis is a layer of loose connective tissue underlying the dermis. With an ambiguous border, it merges into the dermis.