Hårsækkens

Hårsækken, also known as a hair follicle, is a vital structure in the skin responsible for producing hair. It is a small, tubular invagination of the epidermis that extends down into the dermis. Each hair follicle contains a hair root, which is anchored in the follicle's base.

The development of a hair follicle begins during fetal development. At the bottom of the follicle is a bulb, which houses the dermal papilla, a small cone of connective tissue containing capillaries that nourish the growing hair. Surrounding the dermal papilla is the hair matrix, a layer of actively dividing epidermal cells. These cells differentiate and keratinize to form the hair shaft, which is the visible part of the hair.

Associated with each hair follicle is a sebaceous gland, which secretes sebum, an oily substance that lubricates the hair and skin. A small erector pili muscle is also attached to the follicle; when this muscle contracts, it causes the hair to stand on end, a phenomenon commonly known as goosebumps.

Hair follicles go through a cyclical process of growth and rest. This cycle, known as the hair growth cycle, consists of three main phases: anagen (growth phase), catagen (transitional phase), and telogen (resting phase). The duration of each phase varies depending on the body location and individual factors.

The health and function of hair follicles are crucial for hair growth and the overall condition of the skin. Various factors, including genetics, hormones, nutrition, and environmental influences, can affect hair follicle activity and lead to conditions like hair loss.