MEDICAL ANIMATION TRANSCRIPT: A pressure injury or ulcer is a wound caused by constant pressure on your skin. It may also be called a pressure sore, pressure ulcer, bed sore, or decubitus ulcer. Pressure injuries occur most frequently in areas where your bones are close to the skin, including your heels, ankles, hips, tailbone, or elbows. In order to understand how pressure injuries happen, it's important to know about the layers of the skin. Your skin is made up of three main layers. The top layer, called the epidermis, is a thin layer that protects your body from the environment. The thicker middle layer is called the dermis. Its main functions are to supply the epidermis with nutrients, help regulate your body temperature, and provide strength and elasticity to your skin. The innermost layer is called the hypodermis or subcutaneous layer. This layer stores fat, which cushions the muscles and bones beneath it. In a pressure injury, constant pressure on the skin over a long period of ...