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The vomer (; lat, vomer, lit=ploughshare) is one of the unpaired facial bones of the
skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, th ...
. 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 perpendicular plate of the ethmoid bone (vertical plate) is a thin, flattened lamina, polygonal in form, which descends from the under surface of the cribriform plate, and assists in forming the septum of the nose; it is generally deflected ...
. The name is derived from the Latin word for a ploughshare and the shape of the bone.


In humans

The vomer is situated in the median plane, but its anterior portion is frequently bent to one side. It is thin, somewhat quadrilateral in shape, and forms the hinder and lower part of the nasal septum; it has two surfaces and four borders. The surfaces are marked by small furrows for
blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide awa ...
s, and on each is the
nasopalatine groove The nasopalatine nerve (long sphenopalatine nerve) is a nerve of the head. It is a branch of the pterygopalatine ganglion, a continuation from the maxillary nerve (V2). It supplies parts of the palate and nasal septum. Structure The nasopalati ...
, which runs obliquely downward and forward, and lodges the nasopalatine nerve and vessels.


Borders

The ''superior border'', the thickest, presents a deep furrow, bounded on either side by a horizontal projecting expansion of bone – called the wing of vomer; the furrow receives the rostrum of the sphenoid, while the margins of the alae articulate with the vaginal processes of the medial pterygoid plates of the sphenoid behind, and with the sphenoidal processes of the palatine bones in front. The ''inferior border'' articulates with the crest formed by the maxillæ and palatine bones. The ''anterior border'' is the longest and slopes downward and forward. Its upper half is fused with the perpendicular plate of the ethmoid; its lower half is grooved for the inferior margin of the septal cartilage of the nose. The ''posterior border'' is free of bony articulation, having no muscle attachments. It is concave, separates the
choana The choanae (singular choana), posterior nasal apertures or internal nostrils are two openings found at the back of the nasal passage between the nasal cavity and the throat in tetrapods, including humans and other mammals (as well as crocodili ...
e, and is thick and bifid above, thin below.


Articulations

The human vomer articulates with six bones: * two of the cranium, the sphenoid and ethmoid. * four of the face, two
maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) 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. T ...
e; and two palatine bones. It also articulates with the septal cartilage of the nose.


Vomeronasal organ

The
vomeronasal organ The vomeronasal organ (VNO), or Jacobson's organ, is the paired auxiliary olfactory (smell) sense organ located in the soft tissue of the nasal septum, in the nasal cavity just above the roof of the mouth (the hard palate) in various tetrapo ...
, also called Jacobson's organ, is a chemoreceptor organ named for its closeness to the vomer and
nasal bone The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face and by their junction, form the bridge of the upper one third of the nose. Ea ...
s, and is particularly developed in animals such as cats (who adopt a characteristic pose called the ''
Flehmen reaction The flehmen response (; from German ''flehmen'', to bare the upper teeth, and Upper Saxon German ''flemmen'', to look spiteful), also called the flehmen position, flehmen reaction, flehmen grimace, flehming, or flehmening, is a behavior in which ...
'' or ''flehming'' when making use of it), and is thought to have to do with the perception of certain pheromones.


In other animals

In
bony fish Osteichthyes (), popularly referred to as the bony fish, is a diverse superclass of fish that have skeletons primarily composed of bone tissue. They can be contrasted with the Chondrichthyes, which have skeletons primarily composed of cartil ...
, the vomers are flattened, paired, bones forming the anterior part of the roof of the mouth, just behind the
premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has ...
ry bones. In many species, they have teeth, supplementing those in the jaw proper; in some labyrinthodonts (extinct amphibians) the teeth on the vomers were actually larger than the primary set. In amphibians and
reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates ( lizards and snakes) and rhynchocephalia ...
s, the vomers become narrower, due to the presence of the enlarged
choana The choanae (singular choana), posterior nasal apertures or internal nostrils are two openings found at the back of the nasal passage between the nasal cavity and the throat in tetrapods, including humans and other mammals (as well as crocodili ...
e (the inner part of the nostrils) on either side, and they may extend further back in the jaw. They are typically small in
bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
s, where they form the upper hind part of the beak, again being located between the choanae. In some living
salamander Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All t ...
s, including the mudpuppy, the
maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) 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. T ...
is absent and therefore the vomerine teeth fulfill a major functional role in the upper jaw. In
mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur ...
s, the vomers have become narrower still, and are fused into a single, vertically oriented bone. The development of the hard palate beneath the vomer means that the bone is now located in a nasal chamber, separate from the mouth.


Additional images

Image:Sobo 1909 73.png Image:Sobo 1909 74.png Image:Sobo 1909 75.png Image:Gray173.png, Median wall of left nasal cavity showing vomer ''in situ.'' Image:Gray174.png, The vomer. Image:Gray187.png, Base of skull. Inferior surface. Image:Gray194.png, Sagittal section of skull. File:Rotation Vomer bone.gif File:Vomer.jpg, Vomer File:Slide7qqq.JPG, Vomer


See also

*


References


External links

* – "Nasal Cavity: Bones" * – "Diagram of skeleton of medial (septal) nasal wall." * () * – "Nasal septum, lateral view" * * {{Authority control Bones of the head and neck Irregular bones Facial bones Flat bones