Several types of sensory structures give the skin its relationship function with the environment.
Distributed throughout the skin, they are basically dendrites of sensory neurons (free nerve endings), some of which are encased in a capsule of connective or epithelial cells, so these receptors are capsulated.
Three skin structures derived from the epidermis are extremely important in the adaptation of mammals to the terrestrial environment: hair, which assists in thermal isolation; sweat glands, which play the important role in regulating body temperature; and sebaceous glands, which lubricate the skin and attached structures.
The skin is a type of epithelial tissue called the lining epithelium. Lining epithelial tissues are also found lining the inner body cavities of animals.