The hair root is the part of the hair that is located below the surface of the skin. It is attached to the hair follicle, which is a tube-like depression in the skin. The hair root is made up of two parts: the hair bulb and the hair shaft.
The hair bulb is the lower part of the hair root. It is located at the base of the hair follicle. The hair bulb is made up of a layer of cells called the hair matrix. The hair matrix cells are constantly dividing and producing new hair cells. These new hair cells are pushed up through the hair follicle and eventually emerge from the skin as a new hair. The hair root comprises several essential components, including:
- Hair bulb: The hair bulb is a club-shaped structure at the base of the hair root that provides nourishment for the growing hair strand. It houses the dermal papilla, matrix cells, and melanocytes, which are crucial for hair growth and pigmentation.
- Dermal papilla: The dermal papilla, or hair papilla, is a cone-shaped elevation that fits into the hair bulb. It consists of connective tissue, blood vessels, and specialized cells that supply essential nutrients and oxygen to the hair follicle, supporting hair growth and regulating the hair growth cycle.
- Matrix cells: Surrounding the dermal papilla within the hair bulb, matrix cells are responsible for producing the hair shaft and the inner root sheath. These cells rapidly divide and differentiate, pushing older cells upward, which then undergo keratinization to form the hair strand.
- Inner root sheath: The inner root sheath surrounds and guides the growing hair strand as it emerges from the follicle. It consists of three layers (Henle’s layer, Huxley’s layer, and the cuticle) and helps shape the hair strand.
The hair shaft is the upper part of the hair root. It is the part of the hair that is visible above the surface of the skin. The hair shaft is made up of dead, keratinized cells. Keratin is a protein that gives the hair its strength and structure.
The hair root is susceptible to a number of conditions, including:
- Alopecia areata
- Trichotillomania
- Traction alopecia
- Infections
- Tumors