Oxygenated blood from lungs enters left atrium, goes to left side of ventricle, then out through systemic part of conus. Inflation of lungs is by contraction of throat, not expansion of body cavity. Gills, when present, are dermal. Ophistonephric, as in fishes. Since most amphibians are freshwater, nephrons are well-developed.
Most amphibians lack scales.
Skin contains numerous mucus glands to keep it soft and moist for respiration. The skin is periodically shed in molts. In more terrestrial amphibians, brooding occurs in various forms, along with reduction of larval phase. Braincase not well ossified. Ribs generally lacking.