Posterior nasal apertures

The posterior nasal apertures or internal nostrils are found at the posterior (back part) of the nasal passage between the nasal cavity and the throat in tetrapods with secondary palates, including humans and other mammals (as well as crocodilians and most skinks). In animals with secondary palates, they allow breathing when the mouth is closed. They are also known as the choanae (singular choana) (from Greek χοάνη "funnel"). In tetrapods without secondary palates their function relates primarily to olfaction (sense of smell).