The dermis is a connective tissue layer under the epidermis, and contains nerve endings, sensory receptors, capillaries , and elastic fibers. The integumentary system has multiple roles in homeostasis, including protection, temperature regulation, sensory reception, biochemical synthesis, and absorption. All body systems work in an interconnected manner to maintain the internal conditions essential to the function of the body. The sweat glands open to the surface through the skin pores. The hair shaft extends above the skin surface, the hair root extends from the surface to the base or hair bulb .
Nails consist of highly keratinized, modified epidermal cells.
Cells forming the nail bed are linked together to form the nail. The skin's primary functions are to serve as a barrier to the entry of microbes and viruses, and to prevent water and extracellular fluid loss. Acidic secretions from skin glands also retard the growth of fungi. Heat and cold receptors are located in the skin. The hypothalamus also causes dilation of the blood vessels of the skin, allowing more blood to flow into those areas, causing heat to be convected away from the skin surface.