A chamber at the oral end of the vertebrate alimentary canal, leading to the esophagus. Because of divergent specializations in the various classes of vertebrates, it cannot be described in general terms except at embryonic stages. In adult humans it is divided anteriorly by the soft palate into a nasopharynx and an oropharynx, lying behind the tongue but anterior to the epiglottis; there is also a retropharyngeal compartment, posterior to both epiglottis and soft palate. The nasopharynx receives the nasal passages and communicates with the two middle ears through auditory tubes. The retropharynx leads to the esophagus and to the larynx, and the paths of breathing and swallowing cross within it. In adult fishes, the pharynx is not segregated from the mouth cavity but is pierced by a number of paired gill slits.