Choane

Base of the cat's skull (Choanen outlined with a dashed line, ventral part of the palatine bone orange, vomer blue)

As Choane (ancient Greek for 'funnel') or choanae is called the paired opening of the nasal cavity ( nasal cavity ) in the mouth or pharynx . It lies at the base of the skull and is also called the inner nostril, in contrast to the outer nostril with the cartilage-supported nostrils ( nares ). It is a structural feature of the osteolepiformes , the lung fish and the terrestrial vertebrates , which are therefore also grouped together to form the Choanata .

In mammals , the choane is bounded by the palatine bone ( os palatinum ) and the anterior part of the sphenoid bone ( os sphenoidale ). Here the ventral (lower) nasal passage of the nasal cavity ( Meatus nasi ventralis ) merges with the Meatus nasopharyngeus (nasopharyngeal duct) on both sides into the nasopharynx ( Pars nasalis pharyngis ). In mammals, the two choan openings are separated from each other by the ploughshare ( vomer ).

In birds, the two palatal bones limit the choane. The vomer is rudimentary in many birds, so that an undivided opening of the choana occurs here. A distinction is made between an anterior ( pars rostralis ) and a posterior section ( pars caudalis ). The latter lies behind the palatal processes of the upper jaw and corresponds to the choane of mammals, while the rostral part corresponds to the palatal suture.

In some fish there is a connection between the nasal and oral cavities (→ fish nose ).

Individual evidence

1. ^ Franz-Viktor Salomon: Bony skeleton. In: Franz-Viktor Salomon, Hans Geyer, Uwe Gille (Ed.): Anatomy for veterinary medicine. 2nd, revised and expanded edition. Enke, Stuttgart 2008, ISBN 978-3-8304-1075-1 , p. 101.
2. ^ Franz-Viktor Salomon: Textbook of poultry anatomy . G. Fischer, Jena et al. 1993, ISBN 3-334-60403-9 , pp. 175-176 .