Final answer:
First-degree burns affect the epidermis, second-degree burns affect both the epidermis and dermis, and third-degree burns extend into deeper layers of the skin. The 'rule of nines' is used to determine the extent of burned skin.
Step-by-step explanation:
The important features that distinguish first, second, and third-degree burns are the depth of the burn and the extent of tissue damage. A first-degree burn affects only the epidermis and is characterized by redness, pain, and swelling. Second-degree burns go deeper and also affect a portion of the dermis, resulting in blistering and more severe pain. Third-degree burns extend into the epidermis and dermis, destroying tissue and affecting nerve endings and sensory function.
The 'rule of nines' is used to determine the extent of burned skin. This method assigns a percentage value to specific anatomical areas, with a total of 9% for each arm, 18% for each leg, 9% for the head, 18% for the chest and abdomen, 1% for the genitals, and 1% for the back. By adding up these percentages, the total body surface area burned can be estimated. This information helps guide treatment decisions and prognosis.