The hair follicles extend down into the dermis or even the hypodermis of the skin. Hair follicles produce all the hair on the body. The deep end of the hair follicle forms a “hair bulb.”
A hair papilla (knot of capillaries) protrudes into the hair bulb and nourishes it. The hair root is encased in and external and internal root sheath.
Sebaceous glands are wrapped around the hair follicles. They secret an oily sebum that keeps hair pliable and helps waterproof the skin to prevent dehydration.
The smallest muscles of the body are found attached to the hair follicles. They are called arrector pili muscles. These smooth muscle fibers extend from the wall of the hair follicle to the epidermis. When exposed to a cool breeze, the muscle will contract and pull the hair straight up. This is how goose bumps are formed.
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Amsel, Sheri. "Hair Follicle" Exploring Nature Educational Resource ©2005-2019. March 18, 2019
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