The essential organs of respiration are the lungs. The ancillary organs include the airways, which lead air to and from the lungs for gas exchange with bloodstream.

The nose is also included, although it may alternatively be considered among the organs of special sense because it evolved as the organ of olfaction. The pharynx, in which the air and food streams cross, is more conveniently considered among the digestive organs, although its upper part (nasopharynx) is purely an airway. A short account of the development follows the description of the adult anatomy.