The papillary layer is the outer layer of the dermis, while the reticular layer is the inner layer of the dermis. According to the National Cancer Institute, both layers contain collagen fibers. Those of the papillary layer are arranged in a thin sheet, while those of the reticular layer are thicker and deposited in parallel with the surface of the skin.
The papillary layer’s primary job is to supply nutrients to various parts of the epidermis, or outer skin layer, and to regulate the body’s temperature. To do so, the papillary layer makes use of a specialized vascular system located within the layer. The National Cancer Institute explains that this vascular system maintains the body’s temperature by increasing or decreasing the amount of blood flow that passes through this layer. For instance, if the air temperature is very low, the body will constrict these blood vessels to prevent the blood from being cooled and cooling the rest of the body. By contrast, a body that is too warm can increase the supply of blood to the skin, which will help to radiate some of the body’s excess heat, achieving a cooling effect.
The National Cancer Institute describes the reticular layer as thicker than the papillary layer, and more responsible for structure, support and elasticity. The reticular layer contains structures such as sebaceous glands, hair follicles and sweat glands.