The Science of Hair
The science of hair is amazing and complex. It consists of three distinct phases: anagen, catagen and telogen. The anagen phase is the growing phase of hair. The follicle contains blood vessels in the papilla, which feeds the growing hair strands. The hair shaft is the part of the follicle that sticks out above the epidermis. As the hair grows towards the epidermis, the stem cells die off, deprived of nourishment. The catagen phase follows, a slowing down of hair growth. In this phase, the blood supply to the follicle stops and cell division slows down. The duration of the catagen phase varies between 2 and 3 weeks.
The hair follicle has two types of cells: the outer layer and the inner root sheath. The outer layer contains the dermal papilla, the surface of the skin where the hair follicle is located. This layer contains the melanocytes and Langerhans cells, which have different jobs in the hair follicle. They play a sensory role in the hair follicle and function as an immunologic sentinel.
The sebaceous glands that produce hair are located in the scalp. They produce oil that makes hair waterproof and shiny. During puberty, the sebaceous glands can produce too much oil and make the hair appear greasy. The body loses approximately 50 to 100 hairs every day, but new ones are constantly replacing them. The hair shafts will fall out or thin, and the hair will begin to fall out in other areas.
Hair grows on the head from the scalp. This hair follicle is a saclike hole in the skin that houses a cluster of special cells. These cells reproduce to make new hair cells. These new hair cells are then attached to the root of the follicle, causing the strand to grow longer and thicker. During anagen I to V, the hair follicle is attached to the skin and a new shaft appears from the dermal papilla.
The follicles are the cells that produce hair. The hair follicles are found in each limb, and each follicle produces hair in a different way. The follicles in the scalp are called dermal follicles, and they have different functions. The cuticle is the outermost layer of the hair. The telogen effluvium is the temporary hair loss that happens on the head.
Hair growth is a process in which the hair follicles proliferate. They grow downward from the scalp and develop into a hair shaft. The follicles form a bulb and the new hair shaft begins to grow out in other parts of the scalp. As a result, the follicles will grow at different rates. In some cases, the follicles will not grow at all. If this occurs, the follicles will remain in the anagen phase for a long time.