The pit does not have any magical properties. What turns the guac brown is the air. If you can keep air from touching the guac then it will stay green. The pit will keep a portion away from the air, but what is more affective is to put plastic wrap over it and push it right down onto the surface.
Denuded skin is just another way of saying that the top layer (epidermis) of skin is gone...either from friction (abrasion or tear), trauma (tape burns), or severe rashes, or from a stage II pressure ulcer.
Previously called decubitus or bed sore, a pressure ulcer is the result of damage caused by pressure over time causing an ischemia of underlying structures. Bony prominences are the most common sites and causes. There are many risk factors that contribute to the development of pressure ulcers.