Final answer:
The hair follicle unit consists of the hair follicle, hair root, hair bulb, dermal papilla, sebaceous gland, and arrector pili muscle and is responsible for hair growth and maintenance.
Step-by-step explanation:
The unit that contains the hair follicle and its appendages, such as the hair root, bulb, dermal papilla, sebaceous gland, and arrector pili muscle, is referred to as the hair follicle unit. Hair is a keratinous filament growing from the epidermis and is predominantly made of dead, keratinized cells. Hair follicles are the structures from where hairs originate, with each follicle containing an associated sebaceous gland that secretes sebum to coat and waterproof the hair.
The arrector pili muscle is a tiny muscle connected to each follicle, capable of causing hair to stand up (a reaction known as 'goosebumps'). The hair matrix is a layer of basal cells that are mitotically active, which along with the hair root, is anchored in the hair follicle, lying below the skin's surface. The hair root ends at the hair bulb in the dermis, which surrounds the hair papilla - a mass filled with connective tissue, blood capillaries, and nerve endings vital for hair growth.