The three basic requirements for efficient gas exchange in all animals:
A thin respiratory membrane is required for fast and efficient diffusion of gases between the environment and the tissues of the organism. As a result, gas exchange systems in animals require a thin layer of cells where diffusion can be fast. A moist requirement is required for the efficient dissolving of gases. The efficient diffusion of gases from air to a connective tissue through lipid membranes requires the liquid interface where air gases are dissolved. Finally, diffusion efficiency directly depends on the surface area. This property increases the amounts of gases that can be absorbed per unit time. Gas exchange systems have increased surface area significantly improving gas exchange.