The skin is an organ that serves many functions, including the important job of being the first line of defense against pathogens and preventing loss of fluids from the body via evaporation. When the skin barrier is breached, not only does a painful injury result, but the wound is prone to infection, which may become systemic. In addition, injury to the skin with a large surface area can mean major loss of fluids from the body. This is often the case with severe burning.
The skin in mammals is composed of two major tissue layers: the epidermis and the dermis. The epidermis is the thin outer layer of the skin, composed of stratified squamous epithelial cells. The epidermis does not have a blood supply of its own. The outermost part of the epidermis is composed of cells that are dead and contain a high concentration of the protein keratin. This layer constantly sloughs off. Underneath these dead, keratinized cells, an actively dividing layer of cells replaces the cells that are lost. The epidermis functions mainly as a waterproof barrier.
The dermis is the layer of skin underneath the epidermis. It is composed mainly of collagen and elastin-containing connective tissue and contains sweat glands, hair follicles, blood vessels, and sensory nerve endings which transmit sensations of pain, itch, and temperature. Underneath the dermis, a connective tissue and fat layer referred to as the hypodermis, which is not considered part of the skin, attaches the skin to the underlying muscle tissue and bone.
The severity of a burn is classified based on depth and surface area affected. The greater the surface area of the body burned, the more severe the burn is and the greater the risk to the burn victim. The “degree” of a burn refers to which skin layers are affected by the burn. In a first degree burn, the epidermis is the only skin layer affected. Healing time is short for first degree burns, and the burn is painful.
In a second degree burn, part of the dermis is also affected. Second degree burns can be classified as superficial partial thickness if only the upper layer of the dermis is affected, or deep partial thickness if the injury extends deeper into the dermis. Blistering occurs, the burn is painful, and the wound takes several weeks to heal. Skin grafting or excision of the burned tissue may be required. A second degree burn may progress to a third-degree burn over time.
In a third degree burn, the entire dermis is affected. The burn is painless, as pain receptors have been destroyed. Excision is required because the skin will not heal on its own. Fourth degree burns are burns in which the tissue underneath the skin, including the hypodermis, muscle, and bone, is also damaged. The affected tissue must be removed in this case.
Burn injuries are not only painful, but incredibly dangerous. Not only does the breach of the skin barrier make the burn victim prone to infection and loss of fluids, but the injuries may be unable to heal on their own and skin grafting or excision may be required. Educate yourself about fire and burn injury prevention, and if you have been burned, seek medical attention immediately.