Lungs are not entirely the sole property of vertebrates, some terrestrial snails have a gas exchange structures similar to those in frogs. Images from W.H. Freeman and Sinauer Associates, used by permission. Diffusion of oxygen from the medium into the blood. Transport of oxygen to the tissues and cells of the body. Diffusion of oxygen from the blood into cells.
Carbon dioxide follows a reverse path.
Image from W.H. Freeman and Sinauer Associates, used by permission. This system includes the lungs, pathways connecting them to the outside environment, and structures in the chest involved with moving air in and out of the lungs. Image from W.H. Freeman and Sinauer Associates, used by permission. Air enters the body through the nose, is warmed, filtered, and passed through the nasal cavity. The vocal cords are two bands of tissue that extend across the opening of the larynx.