The vomer (; lat, vomer, lit=ploughshare) is one of the unpaired

facial bones The facial skeleton comprises the ''facial bones'' that may attach to build a portion of the skull. The remainder of the skull is the braincase. In human anatomy and development, the facial skeleton is sometimes called the ''membranous viscerocr ...

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 Maxillary means "related to the maxilla (upper jaw bone)". Terms containing "maxillary" include: * Maxillary artery *Maxillary nerve In neuroanatomy, the maxillary nerve (V) is one of the three branches or divisions of the trigeminal nerve, ...

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 deflecte ...

. 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 vessels, 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 nasopalatin ...

, 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 bone 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. (''Palate'' is derived from the Latin ''pa ...

s. 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 choanae, 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 maxillae; and two

s. It also articulates with the septal cartilage of the nose.

Vomeronasal organ

The vomeronasal organ, 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. Eac ...

s, and is particularly developed in animals such as cats (who adopt a characteristic pose called the '' Flehmen reaction'' or ''flehming'' when making use of it), and is thought to have to do with the perception of certain pheromones.

In other animals

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 cartilag ...

, the vomers are flattened, paired, bones forming the anterior part of the roof of the mouth, just behind the premaxillary bones. In many species, they have teeth, supplementing those in the jaw proper; in some

labyrinthodont "Labyrinthodontia" (Greek, 'maze-toothed') is an informal grouping of extinct predatory amphibians which were major components of ecosystems in the late Paleozoic and early Mesozoic eras (about 390 to 150 million years ago). Traditionally consid ...

s (extinct amphibians) the teeth on the vomers were actually larger than the primary set. In

amphibian Amphibians are tetrapod, four-limbed and ectothermic vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terres ...

s 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 rhynchocephalians ( ...

s, the vomers become narrower, due to the presence of the enlarged choanae (the inner part of the nostrils) on either side, and they may extend further back in the jaw. They are typically small in birds, where they form the upper hind part of the beak, again being located between the choanae. In some living salamanders, including the mudpuppy, the maxilla 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 or ...

s, the vomers have become narrower still, and are fused into a single, vertically oriented bone. The development of the

hard palate The hard palate is a thin horizontal bony plate made up of two bones of the facial skeleton, located in the roof of the mouth. The bones are the palatine process of the maxilla and the horizontal plate of palatine bone. The hard palate spans ...

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

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