What is the difference between gills and lungs?
Gills and lungs are richly vascularized organs that serve for gas exchange between the environment and the circulatory system. The lungs differentiate from gills in that they are saclike structures always internal to the organism and specialized in gas exchange in terrestrial environment. Branchiae, in their turn, are internal or external laminar structures in direct contact with water and specialized in gas exchange in aquatic environment.
