Final answer:
Burns are classified during a physical exam based mainly on depth: first-degree burns affect the epidermis, second-degree burns affect the epidermis and dermis, third-degree burns destroy all layers of skin, and fourth-degree burns extend to muscle and bone.
Step-by-step explanation:
The stages of burns can be differentiated during a physical exam based on the depth of the burn and the appearance of the affected skin. A first-degree burn is superficial, affecting only the epidermis, and presents with pain and swelling; it usually heals on its own. A second-degree burn affects both the epidermis and dermis, causing painful blisters and requiring efforts to keep the area clean to prevent infection. A third-degree burn extends through the epidermis and dermis, destroying tissue and affecting sensory function, and these burns may have a white, red, or black appearance and necessitate medical attention. The most severe, a fourth-degree burn, affects not only all layers of skin but also the underlying muscle and bone, frequently resulting in the least pain due to nerve damage but requiring the most intensive medical intervention, including possible excision and grafting.