Choana

Choana
Choana
	Lateral wall of nasal cavity.
	Dissection of the muscles of the palate from behind. (Choanae visible at center top.)
Details
Identifiers
Latin	choana
TA98	A02.1.00.096
TA2	501
FMA	76585
	Anatomical terminology [ edit on Wikidata]

Last updated December 13, 2023

The choanae (SG: choana), posterior nasal apertures or internal nostrils are two openings found at the back of the nasal passage between the nasal cavity and the pharynx, in humans and other mammals (as well as crocodilians and most skinks). They are considered one of the most important synapomorphies of tetrapodomorphs, that allowed the passage from water to land.^[1]

Boundaries

A choana is the opening between the nasal cavity and the nasopharynx.

It is therefore not a structure but a space bounded as follows:

anteriorly and inferiorly by the horizontal plate of palatine bone,
superiorly and posteriorly by the sphenoid bone
laterally by the medial pterygoid plates.
medially by the Vomer

Etymology

The term is a latinization from the Greek χοάνη, "choanē" meaning funnel.

Choanae in different animals

Early bony fishes (~420 mya) had two pair of nostrils, one pair for incoming water (known as the anterior or incurrent nostrils), and a second pair for outgoing water (the posterior or excurrent nostrils), with the olfactory apparatus (for sense of smell) in between. In the first tetrapodomorphs (~415 mya) the excurrent nostrils migrated to the edge of the mouth, occupying a position between the maxillary and premaxillary bones, directly below the lateral rostral (a bone that vanished in early tetrapods).^[1]

In all but the most basal (primitive) tetrapodomorphs (or "choanates"), the excurrent nostrils have migrated from the edge of the mouth to the interior of the mouth. In tetrapods that lack a secondary palate (basal tetrapods and amphibians), the choanae are located forward in the roof of the mouth, just inside the upper jaw. These internal nasal passages evolved while the vertebrates still lived in water.^[3] In animals with complete secondary palates (mammals, crocodilians, most skinks) the space between the primary and secondary palates contain the nasal passages, with the choanae located above the posterior end of the secondary palate.

In animals with partial secondary palates (most birds and reptiles), the median choanal slit separates the two halves of the posterior half of the palate, connecting the nasal cavity with the buccal cavity (mouth) and the pharynx (throat).^[4]

Fish

Most fish do not have choanae, instead they have two pairs of external nostrils: each with two tubes whose frontal openings lie close to the upper jaw, and the posterior openings further behind near the eyes. A 395-million-year-old fossil lobe-finned fish called Kenichthys campbelli has something between a choana and the external nostrils seen on other fish. The posterior opening of the external nostrils has migrated into the mouth.^[2]

In lungfish, the inner nostrils are regarded as an example of parallel evolution. The fossil lungfish Diabolepis shows an intermediate stage between posterior and interior nostril and supports the independent origin of internal nostrils in the lungfish.^[2]

Hagfishes have a single internal nostril that opens inside the mouth cavity, while chimaeras have open canals that leads water from their external nostrils into their mouths and through their gills.

Related Research Articles

A nostril is either of the two orifices of the nose. They enable the entry and exit of air and other gasses through the nasal cavities. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation. Fish do not breathe through noses, but they do have two small holes used for smelling, which can also be referred to as nostrils.

Lungfish are freshwater vertebrates belonging to the class Dipnoi. Lungfish are best known for retaining ancestral characteristics within the Osteichthyes, including the ability to breathe air, and ancestral structures within Sarcopterygii, including the presence of lobed fins with a well-developed internal skeleton. Lungfish represent the closest living relatives of the tetrapods. The mouths of lungfish typically bear tooth plates, which are used to crush hard shelled organisms.

<span class="mw-page-title-main">Maxilla</span> Upper jaw bone

The maxilla in vertebrates is the upper fixed bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxillary bones are fused at the intermaxillary suture, forming the anterior nasal spine. This is similar to the mandible, which is also a fusion of two mandibular bones at the mandibular symphysis. The mandible is the movable part of the jaw.

<span class="mw-page-title-main">Palatine bone</span> Bone of the facial skeleton

In anatomy, the palatine bones are two irregular bones of the facial skeleton in many animal species, located above the uvula in the throat. Together with the maxillae, they comprise the hard palate.

The vomer is one of the unpaired facial bones of the skull. It is located in the midsagittal line, and articulates with the sphenoid, the ethmoid, the left and right palatine bones, and the left and right maxillary bones. The vomer forms the inferior part of the nasal septum in humans, with the superior part formed by the perpendicular plate of the ethmoid bone. The name is derived from the Latin word for a ploughshare and the shape of the bone.

The nasal cavity is a large, air-filled space above and behind the nose in the middle of the face. The nasal septum divides the cavity into two cavities, also known as fossae. Each cavity is the continuation of one of the two nostrils. The nasal cavity is the uppermost part of the respiratory system and provides the nasal passage for inhaled air from the nostrils to the nasopharynx and rest of the respiratory tract.

Choanal atresia is a congenital disorder where the back of the nasal passage (choana) is blocked, usually by abnormal bony or soft tissue (membranous) due to failed hole development of the nasal fossae during prenatal development. It causes persistent rhinorrhea, and with bilateral choanal atresia and obstructed airway that can cause cyanosis and hypoxia.

<span class="mw-page-title-main">Rhipidistia</span> Clade of vertebrates

Rhipidistia, also known as Dipnotetrapodomorpha, is a clade of lobe-finned fishes which includes the tetrapods and lungfishes. Rhipidistia formerly referred to a subgroup of Sarcopterygii consisting of the Porolepiformes and Osteolepiformes, a definition that is now obsolete. However, as cladistic understanding of the vertebrates has improved over the last few decades, a monophyletic Rhipidistia is now understood to include the whole of Tetrapoda and the lungfishes.

The Tetrapodomorpha are a clade of vertebrates consisting of tetrapods and their closest sarcopterygian relatives that are more closely related to living tetrapods than to living lungfish. Advanced forms transitional between fish and the early labyrinthodonts, such as Tiktaalik, have been referred to as "fishapods" by their discoverers, being half-fish, half-tetrapods, in appearance and limb morphology. The Tetrapodomorpha contains the crown group tetrapods and several groups of early stem tetrapods, which includes several groups of related lobe-finned fishes, collectively known as the osteolepiforms. The Tetrapodomorpha minus the crown group Tetrapoda are the stem Tetrapoda, a paraphyletic unit encompassing the fish to tetrapod transition.

Orthosuchus is an extinct genus of Notochampsidaean crocodyliform that lived during the Early Jurassic, about 196 million years ago. It was first discovered in 1963 in the Red Beds Formation in the Qacha's Nek Province of Lesotho, southern Africa. The characteristics showed on its postcranial skeleton and the skull indicated that it is a Crocodyliform. The finding is significant since some of the characteristics found on this specimen were believed to be absent until Jurassic.

Kenichthys is a genus of sarcopterygian fish from the Devonian period, and a member of the clade Tetrapodomorpha. The only known species of the genus is Kenichthys campbelli, the first remains of which were found in China in 1993. The genus is important to the study of the evolution of tetrapods due to the unique nature of its nostrils, which provide vital evidence regarding the evolutionary transition of fish-like nostrils to the tetrapod choanae.

<span class="mw-page-title-main">Human nose</span> Feature of the human face

The human nose is the most protruding part of the human face. It bears the nostrils and is the first organ of the respiratory system. It is also the principal organ in the olfactory system. The shape of the nose is determined by the nasal bones and the nasal cartilages, including the nasal septum which separates the nostrils and divides the nasal cavity into two.

A nose is a protuberance in vertebrates that houses the nostrils, or nares, which receive and expel air for respiration alongside the mouth. Behind the nose are the olfactory mucosa and the sinuses. Behind the nasal cavity, air next passes through the pharynx, shared with the digestive system, and then into the rest of the respiratory system. In humans, the nose is located centrally on the face and serves as an alternative respiratory passage especially during suckling for infants. The protruding nose that is completely separate from the mouth part is a characteristic found only in therian mammals. It has been theorized that this unique mammalian nose evolved from the anterior part of the upper jaw of the reptilian-like ancestors (synapsids).

Diabolepis is an extinct genus of very primitive lungfish which lived about 400 million years ago, in the Early Devonian period of South China. Diabolepis is the most basal known dipnoan.

Megalichthyidae is an extinct family of tetrapodomorphs which lived from the Middle–Late Devonian to the Early Permian. They are known primarily from freshwater deposits, mostly in the Northern Hemisphere, but one genus (Cladarosymblema) is known from Australia, and the possible megalichthyid Mahalalepis is from Antarctica.

The pharynx is the part of the throat behind the mouth and nasal cavity, and above the esophagus and trachea. It is found in vertebrates and invertebrates, though its structure varies across species. The pharynx carries food to the esophagus and air to the larynx. The flap of cartilage called the epiglottis stops food from entering the larynx.

Glanosuchus is a genus of scylacosaurid therocephalian from the Late Permian of South Africa. The type species G. macrops was named by Robert Broom in 1904. Glanosuchus had a middle ear structure that was intermediate between that of early therapsids and mammals. Ridges in the nasal cavity of Glanosuchus suggest it had an at least partially endothermic metabolism similar to modern mammals.

The skull roof, or the roofing bones of the skull, are a set of bones covering the brain, eyes and nostrils in bony fishes and all land-living vertebrates. The bones are derived from dermal bone and are part of the dermatocranium.

This glossary explains technical terms commonly employed in the description of dinosaur body fossils. Besides dinosaur-specific terms, it covers terms with wider usage, when these are of central importance in the study of dinosaurs or when their discussion in the context of dinosaurs is beneficial. The glossary does not cover ichnological and bone histological terms, nor does it cover measurements.

Innovations conventionally associated with terrestrially first appeared in aquatic elpistostegalians such as Panderichthys rhombolepis, Elpistostege watsoni, and Tiktaalik roseae. Phylogenetic analyses distribute the features that developed along the tetrapod stem and display a stepwise process of character acquisition, rather than abrupt. The complete transition occurred over a period of 30 million years beginning with the tetrapodomorph diversification in the Middle Devonian.

References

1 2 Clack, Jennifer (2012). Gaining Ground: The Origin and Evolution of Tetrapods. Indiana University Press. p. 74. ISBN 978-0-253-35675-8 . Retrieved 5 August 2015.
1 2 3 Janvier, Philippe (2004) "Wandering nostrils". Nature, 432 (7013): 23–24. doi : 10.1038/432023a
↑ Linzey, Donald W. (2012). Vertebrate Biology. JHU Press. pp. 150–1. ISBN 978-1-4214-0040-2 . Retrieved 8 August 2015.
↑ Farner, Donald S. (22 October 2013). A. J. Marshall (ed.). Biology and Comparative Physiology of Birds. Elsevier Science. p. 412. ISBN 978-1-4832-6379-3 . Retrieved 8 August 2015.

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.

[Clack2012-1] 1 2 Clack, Jennifer (2012). Gaining Ground: The Origin and Evolution of Tetrapods. Indiana University Press. p. 74. ISBN 978-0-253-35675-8 . Retrieved 5 August 2015.

[Janvier2004-2] 1 2 3 Janvier, Philippe (2004) "Wandering nostrils". Nature, 432 (7013): 23–24. doi : 10.1038/432023a

[Linzey2012-3] Linzey, Donald W. (2012). Vertebrate Biology. JHU Press. pp. 150–1. ISBN 978-1-4214-0040-2 . Retrieved 8 August 2015.

[Marshall2013-4] Farner, Donald S. (22 October 2013). A. J. Marshall (ed.). Biology and Comparative Physiology of Birds. Elsevier Science. p. 412. ISBN 978-1-4832-6379-3 . Retrieved 8 August 2015.

[1]

[2]

[3]

[4]