Hair follicles produce hair. They’re found in the dermis layer of the skin. There are several features that make up the hair follicle including the papilla, the matrix, the root sheath, and the bulge.
The papilla is a small, nipple-like protrusion found at the base of a hair follicle. Papilla extend from the dermis into the epidermis and are mostly made up of connective tissue. When the papilla are found on the epidermis, they create ridge-like marks that are called fingerprints. The matrix surrounds the papilla.
The root sheath, which consists of both an external and an internal root sheath that consists of three different layers, protects the hair follicles. The bulge can be found in the outer root sheath, where it holds several kinds of stem cells. These supply the hair follicle with new cells and help heal the skin after it has suffered a wound.
Hair grows in three different stages: the anagen phase, the catagen phase, and the telogen phase. Every hair follicle is at a different stage of the cycle, which is why laser hair removal requires several treatments. During the anagen phase, hair grows approximately one centimeter per day. The amount of time spent in this stage is determined both by the location of the hair on the body and genetics. For example, the scalp typically remains in this stage between two and seven years.
The next phase is the catagen phase, when hair stops growing and becomes a club hair, which is cut off from the blood supply and the cells that produce hair growth. The process only takes a few weeks before the hair enters the telogen phase, or the rest stage, when hair falls out.