Final answer:
The small involuntary muscles attached to each hair follicle are called arrector pili. These muscles contract and cause the hair to stand up, a phenomenon often recognized as 'goosebumps.' Hair follicles originate in the skin's dermis and are associated with sebaceous glands that produce sebum.
Step-by-step explanation:
The small bundle of involuntary muscles attached to each hair follicle are known as arrector pili muscles. These muscles contract in response to certain stimuli, such as cold or fear, causing the hair in the follicle to stand up. This reaction is commonly recognized as 'goosebumps.' The hair follicle itself is an epidermal penetration of the dermis from which hair originates. Hair is primarily composed of dead, keratinized cells, and its growth begins at a structure called the hair bulb, which is located at the base of the follicle. The hair bulb is surrounded by the hair matrix, a layer of basal cells that undergo mitosis, allowing the hair to grow. Intertwined with the dermis layer of the skin, the follicle is also associated with sebaceous glands producing sebum to lubricate the hair and skin.