Hair follicle anatomy: MedlinePlus Medical Encyclopedia Image (2024)

FAQs

What is the anatomy of the hair follicle? ›

A hair follicle is a tube-like structure (pore) that surrounds the root and strand of a hair. Hair follicles exist in the top two layers of your skin. You're born with over 5 million hair follicles in your body and over one million hair follicles on your head.

Pores are just glorified hair follicles

Pores are simply the opening of hair follicles, which extend down further through several layers of skin. Each follicle/pore contains or has the ability to grow one shaft of hair, whether that hair is visible or not.

Sebaceous glands develop on or near your hair follicles in the second layer of your skin (dermis). You have thousands of sebaceous glands all over your body. The only place where you don't have sebaceous glands are on the palms of your hands and the soles of your feet.

The shaft is the visible part of the hair that sticks out of the skin. The hair root is in the skin and extends down to the deeper layers of the skin. It is surrounded by the hair follicle (a sheath of skin and connective tissue), which is also connected to a sebaceous gland.

A hair follicle consists of two main layers, an inner (epithelial) root sheath and an outer (fibrous) root sheath. At the base of the hair follicle is the hair bulb, which houses the dermal papillae and hair matrix cells. The hair bulb and inner epithelial layer generates hair.

Scalp buildup can cause hair loss if left untreated and the dead skin, oil, and sweat clog your hair follicles. This can lead to an uncomfortable condition called folliculitis. Folliculitis causes inflammation of the hair follicles that sometimes results in infection.

Sebaceous filaments help move oil from your sebaceous glands to the surface of your skin. They sometimes look large and can be confused for blackheads, but they help keep your skin hydrated. Age, skin care and the thickness of hair follicles determine how noticeable they are.

Blocked hair follicles start out like pimples. If they get worse, they can grow deep into the skin and look more like cysts or boils. They may also burst and leak pus or blood. They can make tunnels under your skin.

What is the black stuff in my hair follicle? The "black stuff" in a hair follicle could be a number of things, but it's usually dirt, oil, or product buildup.

Breast boils occur when a hair follicle becomes infected by bacteria. The infection causes the area to become inflamed, red, and painful. Pus may leak from the boil or need to be surgically drained. Wearing a well-fitted bra and keeping the breasts dry and clean can help prevent breast boils from forming.

How deep is a hair follicle? ›

Results: The mean length of a scalp hair follicle is 4.16 mm. The infundibulum measures 0.76 mm, the isthmus 0.89 mm, and the inferior portion 2.5 mm. The insertion of the arrector pili muscle is located 1.65 mm deep. CK15 immunoreactivity starts at a depth of 1 mm and extends down to 1.8 mm.

"The white bulb at the end of the hair is keratin (or protein) and is the same keratin that makes up your skin and nails. A white bulb is not indicative of hair loss," said stylist Carrie Capalbo of Salon YOSHIKO. "It's part of the lining of the hair follicles.

Pulling out hair by your root may damage your follicle temporarily, but a new bulb will eventually form, and new hair will grow again through that follicle. According to the TLC Foundation for Body-Focused Repetitive Behaviors, it may take a few months or more than a year in some cases.

So, if you notice black hair roots, it's because your melanocytes have been producing melanin normally. Interestingly, melanin production can restart after a period of dormancy, which can lead to a strand of hair that's white or gray on the tip and black closer to the root.

The Hair Bulb

When they reach the upper part of the bulb, they arrange themselves into six concentric layers. The three inner layers become the hair, made up of the cuticle, the cortex and the medulla (although the medulla isn't always present, especially in hairs with a thinner diameter).

The hair shaft is the part of the hair not anchored to the follicle, and much of this is exposed at the skin's surface. The rest of the hair, which is anchored in the follicle, lies below the surface of the skin and is referred to as the hair root.

The hair follicle root, which is located 4mm under the epidermis, includes sebaceous glands and interacts with the associated structures (epidermis, dermis, arrector pili muscles, vascular system).