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The dermal papilla is a group of cells that form the structure directly below the hair follicle. These cells supply glucose to the follicle, which is needed for energy and the production of amino acids. This nourishment allows the body to grow new hair.
Receptors for androgens are found in the dermal papilla. Androgens are hormones responsible for hair growth, among other body funcitons. Individuals who have a genetic predisposition to baldness or hair loss may notice that their hair gets increasingly thinner. Androgens can cause hair follicles on the scalp to get smaller, leading to hair thinning and progressing baldness.
The dermal papilla begins to form while a human baby is still in the womb. They begin development by the time an embryo is three months old. They mark the spot for hair follicles that will grow hair later, both in the womb and after birth.
When the hair follicle is in the anagen phase, the dermal papilla is large and the cells are spaced far apart. This opens up the hair follicle so that it can receive energy and keratin, the protein that makes up hair, from the dermal papilla to promote new hair growth. At any given time, about 85 percent of hairs on the human body are in the anagen, or growing, phase.
Hair follicles can stay in this phase for up to six years. After the growth phase is over, the hair follicle enters a transitional phase called the catagen phase for one to two weeks. The follicle gets smaller, to around 1/6 of its previous size, during this transition phase, and the dermal papilla breaks off. The cells flatten and move in together to form a dense ball.
The hair follicle rests in a phase called the telogen phase for about five to six weeks following the transitional phase. Hair does not grow during the resting phase, and the dermal papilla cells remain in a tight cluster below the follicle. Once the hair follicle returns to the growing phase again, the dermal papilla joins with the hair follicle above and initiates new hair growth by providing the follicle with nourishment.
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