Burns can be of various origins—thermal, electrical, chemical, and mechanical--and can cause varying degrees of damage to the body. All burns involve injury to the surface of the skin and to the underlying layers of tissue.

The skin is composed of several layers. The outermost visible layer is the epidermis. This layer sloughs off continuously. Thus, damage to the epidermis is not long lasting. Immediately underneath the epidermis is the dermis, which is composed of connective tissue, blood vessels, nerve endings, hair follicles, and sweat and oil glands. This myriad of functions makes damage to the dermis potentially more damaging and longer lasting. The lowest layer of skin is the hypodermis, or basement membrane. Damage to this layer, the foundation of the skin, constitutes a serious full-thickness injury.

The injuries caused by the various types of burns are classified according to the amount of the body...