The dermal papilla is a type of human skin cell that is located just beneath the epidermis, or outermost layer, of the skin. This sort of cell typically protrudes up through the epidermis to make a small bump. These bumps play a number of important roles, determined largely by location. Hair follicles protrude through them, for instance, and as such they play an important role in hair growth and subsequent loss; they are also integral in creating the ridges and lines characteristic of the inner hands and feet, the same lines that make fingerprints so unique.
Basic Role in Skin Anatomy
Human skin typically has three primary layers which, from the inside out, consist of the hypodermis, the dermis, and the epidermis. Each has a slightly different role when it comes to providing a barrier, sealing in moisture, and supporting things like sweat and hair growth — all essential functions of skin. The dermal papillae are usually though of as small sections of the dermis that push through or pop out of the epidermis. They aren’t always immediately visible on the surface of the skin, but tend to be quite obvious on a microscopic level.
All humans have quite a few of these skin cells, and the protrusions associated with them are an important part of skin health. The bumps anchor most hair follicles, for instance, and also facilitate things like sweat evaporation and water repellency. Together they form a grooved texture that, at least on a cellular level, resists pooling; where hair is concerned, it also provides nutrition to a growing follicle.
One of the most notable roles of these cells is the creation of fingerprints. Rows and rows of the protrusions form rifts and valleys on the fingers and toes that have a swirled, curved look from a distance. Each person has a different pattern of papilla extensions, which in turn leads to a unique fingerprint from birth onwards. In most cases dermal papillae begins to form while a human fetus is still in the womb. Protrusions usually start appearing by about three months’ gestation.
Special Role in Hair Support
Where hair is concerned, the dermal papilla forms 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 is a big part of what allows the body to grow new hair.
Follicle Formation and Early Growth
When the hair follicle is its primary growing phase, also known as the anagen phase, the bumps are 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, to promote new hair growth. At any given time, about 85 percent of hairs on the human body are in their peak growing phase.
Understanding Hair Lifecycle
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 papilla cells remain in a tight cluster below the follicle. Once the hair follicle returns to the growing phase again, the papillae join with the hair follicles above them and initiate new hair growth by providing those follicles with nourishment.
As a Site for Androgen Receptors
Receptors for hormones known as “androgens” are found in this cellular level, too. Androgens are responsible for hair growth, among other body functions. 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.