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.
Hydrostatic pressure is not the only pressure that exists in a blood vessel. We must consider also the hydraulic pressure caused by the pumping of the heart. Hydraulic pressure is the pressure that results from pushing a liquid through a pipe or other channel. Osmotic pressure is also present.