Juuksejuure

Juuksejuur, known in English as the hair root, is the portion of a hair that resides within the hair follicle in the skin. The hair shaft—the part that extends above the skin surface—is produced by cells in the hair root and keratinizes as they move upward.

At its deep end, the hair root includes the hair bulb, which surrounds the dermal papilla that provides blood supply and signals for growth. The hair matrix, a group of rapidly dividing cells, generates the keratinized cells that form the hair fiber. Melanocytes in the matrix give hair its color.

Associated structures include sebaceous glands that secrete sebum into the follicle to lubricate the hair, and the arrector pili muscle that can elevate the hair to create goosebumps.

The hair root follows a growth cycle with three main phases: anagen (growth), catagen (transition), and telogen (rest). Individual hairs vary in duration; scalp hairs typically grow for several years and at a rate of about 1 cm per month, though this varies by location, age, and hormones.

Variations in the hair root and cycle are involved in common conditions such as androgenetic alopecia, telogen effluvium, and alopecia areata. In clinical practice, examination of the hair root and follicle is used to assess hair health and diagnose disorders; factors like nutrition, hormones, and overall health influence growth.