Frog Stomach
This smooth, delicate amphibian skin is also air-permeable, allowing oxygen to pass through. Although frogs have lungs, the ability to absorb oxygen from moist surroundings is especially useful to frogs that burrow deep or hibernate in underwater mud. Covered with mucus-secreting glands that help to keep their slippery skin stay moist and pliable, some frogs can also secrete a waxy substance to keep body water from evaporating.