How are hair follicles formed? Describe the structure of a hair follicle: how are hairs pulled erect? How are sebaceous glands associated with hair follicles; what function does a sebaceous gland perform?
Hair follicles are formed from invaginations of the epidermis. While the hair roots are embedded deep within the dermis, the hair shafts, extending at a slant, project beyond both the dermis and the epidermis to the outside. Each hair follicle has a small muscle running diagonally up from the root through the dermis. When the muscle contracts due to nervous stimulation, it pulls the hair erect. One or more sebaceous glands empty oil into each hair follicle. From the follicle, the oil spreads in a thin layer to cover the outside surface of the skin.
