Vomer

Vomer
Vomer labeled at left.
Bones and cartilages of the nasal septum, right side, with the vomer labeled at center left.
Details
Identifiers
Latinvomer
MeSHD055172
TA98A02.1.11.001
TA2751
FMA9710
Anatomical terms of bone

The vomer (/ˈvoʊmər/; Latin: vomer, lit. 'ploughshare') 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.

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 vomerine groove (also nasopalatine groove or Scarpa's sulcus), which runs obliquely downward and forward, and lodges the nasopalatine nerve (also Scarpa's 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 choanae, and is thick and bifid above, thin below.

Articulations

The human vomer articulates with six bones:

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 bones, 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

Skull of the early reptile Milleretta rubidgei (Millerettidae), showing vomer bones bearing palatal teeth on the underside of the skull (labeled vo, tan, bottom right)

In bony fish, 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 labyrinthodonts (extinct amphibians) the teeth on the vomers were actually larger than the primary set. In amphibians and reptiles, 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 mammals, 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.

"Prevomer"

Historically, there was significant confusion in the homology of the vomer across vertebrate groups. Palaeontologist Robert Broom suggested that the unpaired vomer of mammals was actually equivalent to the unpaired parasphenoid of other vertebrates; further, he proposed that the paired vomers of lizards (and, by extension, other non-mammalian vertebrates) were a separate element, which he called the prevomer; he further argued that the prevomer was homologous to the os paradoxum of the platypus and the palatine process of the premaxilla in other mammals. His work was highly influential.

However, later work determined that, contrary to Broom, the parasphenoid is present in mammals; therefore, the mammalian vomer is not a parasphenoid, but likely resulted from fusion of the paired vomers. The os paradoxum and palatine processes of the premaxilla are separately derived. Nevertheless, the influence of Broom's work led to the term "prevomer" becoming applied to the vomer of fishes, and the term remains in use.

Additional images

See also

References

Public domain This article incorporates text in the public domain from page 170 of the 20th edition of Gray's Anatomy (1918)

  1. ↑ OED 2nd edition, 1989.
  2. ↑ Entry "vomer" in Merriam-Webster Online Dictionary.
  3. ↑ Illustrated Anatomy of the Head and Neck, Fehrenbach and Herring, Elsevier, 2012, page 52
  4. 1 2 Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. pp. 220–243. ISBN 0-03-910284-X.
  5. ↑ Holman, J. Alan (2006). Fossil salamanders of North America. Indiana University Press. ISBN 0-253-34732-7. OCLC 62732645.
  6. 1 2 Wible, John R. (2022-03-15). "The history and homology of the os paradoxum or dumb-bell-shaped bone of the platypus Ornithorhynchus anatinus (Mammalia, Monotremata)". Vertebrate Zoology. 72: 143–158. doi:10.3897/vz.72.e80508. ISSN 2625-8498.
  7. ↑ Iyyanar, Paul P.R.; Qin, Chuanqi; Adhikari, Nirpesh; Liu, Han; Hu, Yueh-Chiang; Jiang, Rulang; Lan, Yu (2023). "Developmental origin of the mammalian premaxilla". Developmental Biology. 503: 1–9. doi:10.1016/j.ydbio.2023.07.005. ISSN 0012-1606. PMC 10528123. PMID 37524195.
  8. ↑ Jollie, Malcolm (1986). "A primer of bone names for the understanding of the actinopterygian head and pectoral girdle skeletons". Canadian Journal of Zoology. 64 (2). NRC Research Press: 365–379. Bibcode:1986CaJZ...64..365J. doi:10.1139/z86-058. ISSN 0008-4301.
  9. ↑ Harrington, Robert W. (1955). "The Osteocranium of the American Cyprinid Fish, Notropis bifrenatus, with an Annotated Synonymy of Teleost Skull Bones". Copeia. 1955 (4). [American Society of Ichthyologists and Herpetologists (ASIH), Allen Press]: 267–290. Bibcode:1955Copei1955..267H. doi:10.2307/1440304. ISSN 0045-8511. JSTOR 1440304.
  10. ↑ Noriega, Jorge I.; Peralta, Matías J.; Monsalvo, Sebastián; Schmidt, Gabriela I.; Diederle, Juan M.; Tarquini, Juliana; Gottardi, M. Griselda; Brunetto, Ernesto; Brandoni, Diego (2025). "A new large species of weakfish (Acanthuriformes: Sciaenidae: Cynoscion ) from the Upper Miocene of Argentina". Journal of Vertebrate Paleontology. 45 (4) e2579188. Bibcode:2025JVPal..4579188N. doi:10.1080/02724634.2025.2579188. ISSN 0272-4634.