Basal cells continually undergo mitosis. Skin is waterproof because keratin, a protein is produced. The next layer is the dermis a layer of fibrous connective tissue. Within the dermis many structures are located, such as sweat glands, hair follicles and oil glands. The subcutaneous layer is composed of loose connective tissue.
Adipose tissue occurs here, serving primarily for insulation.
Nerve cells run through this region, as do arteries and veins. It also maintains pH of the blood and facilitates exchange of carbon dioxide and oxygen. Digestion is accomplished by mechanical and chemical means,breaking food into particles small enough to pass into bloodstream. Absorbtion of food molecules occurs in the small intestine and sends them into circulatory system. The digestive system also recycles water and reclaims vitamins from food in the large intestine .