Posterior nasal apertures
As choana (Latin choana ) is called the paired posterior opening of the nasal cavity ( cavum nasi). The ventral (lower ) meatus of the nasal cavity ( nasal meatus ventralis ) assumes the meatus nasopharyngeus ( nasopharyngeal passage ) on both sides through this opening into the nasal pharynx ( pars nasalis pharyngis ) above.
The choanae are located at the base of the skull and the palatine bone ( palatine bone ) and the anterior part of the sphenoid ( sphenoid ) limited.
The two Choanenöffnungen are separated in mammals by the vomer ( vomer ). The vomer is rudimentary in many birds, so here's a undivided Choanenöffnung occurs.
In some fish there is a connection between the nasal and oral cavity (see nose fish ).