hårfollikel

The hårfollikel, or hair follicle, is a vital structure in mammalian skin responsible for the growth of hair. It is a complex, dynamic organ that cycles through distinct phases of growth, regression, and rest. The follicle is embedded in the dermis and epidermis, with its base extending deep into the dermal layer.

The main components of a hair follicle include the hair bulb, dermal papilla, outer root sheath, inner root sheath, and the hair shaft itself. The hair bulb, located at the base, contains rapidly dividing cells that produce the hair. The dermal papilla, a small cone of connective tissue, provides nutrients and signals to the hair bulb, influencing hair growth. The root sheaths surround the developing hair, providing support and protection.

Hair growth occurs in a cyclical pattern. Anagen is the active growth phase, during which cells in the hair bulb divide and push the hair shaft upwards. This phase can last for several years. Catagen is a transitional phase where cell division stops, and the follicle begins to shrink. Telogen is the resting phase, where the hair remains in the follicle but is no longer growing. Finally, exogen is the shedding phase, where the old hair detaches and falls out, and a new anagen phase begins.

The health and function of hårfollikel are influenced by various factors, including genetics, hormones, nutrition, and overall health. Conditions affecting hair follicles can lead to hair loss (alopecia) or other hair abnormalities. Understanding the intricate workings of the hårfollikel is crucial for comprehending hair biology and addressing related dermatological issues.