Frogs and their skin
Frogs are actually known to shed and eat their own skin like most animals. They do this so they do not waste all the nutritious protein found in their skin. This is the ultimate way to recycle all the components they use to produce their skin.
When frogs start out as tadpoles, they breathe underwater through internal gills. Normally, frogs breath with their mouths closed. Their throat movements pulls air through the nostrils and to the lungs. Frogs can also breath through their skin, with tiny blood vessels, capillaries, under the outer skin layers.
Frogs absorb water directly through their skin in an area known as the 'drinking patch' which is located on their belly and the underside of their thighs.