Topic 1 Summary
The hair follicle is formed in the upper layer of the skin from a cluster of cells. These cells are called the primitive hair germ. Primitive hair germ cells get their nourishment by working their way down into the dermal layer of the skin. As the cells continue to grow, the nucleus of the cells disappears and the cells become keratinized.
The structures of the hair are the sebacous glands or oil glands and the arrector pili. The sebaceous glands are connected to the hair follicle and produce a substance called sebum. Sebum give the hair luster and pliability. The arrector pili is a small involuntary muscle attached to the underside of the hair follicle. The arrector pili muscle is responsible for"goose bumps" when a person is cold or freightened.
The dermal papilla is a small cone-shaped elevation located at the bottom of the hair folicle and fits into the hair bulb. Through the papilla hair receives its nourishment.
Hair goes through three stages of growth: Anagen, the growth stage, which lasts about four years; catagen, the transitional stage, which lasts 2-3 weeks; and telogen, the resting stage, which lasts approximately 100 days. These cycles are repeated continously.