The vomer (Fench: le Vomer) is an irregular four-sided plate of bone constituting the lower portion of the nasal septum. It is usually described as resembling a ploughshare in shape. Each lateral surface is covered with the thick mucous membrane of the nasal sinus, and is traversed by a narrow but well-marked groove, which lodges the naso- palatine nerve from the spheno-palatine ganglion; hence it is sometimes called the naso-palatine groove.
The superior border of the bone is expanded laterally into two alee. The groove between them lodges the rostrum of the sphenoid, whilst the margin of each ala comes into contact with the sphenoidal process of the palate bone. Between the alae and the sphenoid a canal exists on each side of the rostrum for blood-vessels. The inferior border is uneven, and is received into the groove formed by the crests of the opposed maxillae and the palatine bones of each side. The anterior border joins posteriorly the mesethmoid, and in front the triangular (median) nasal cartilage. The posterior border, smooth, rounded, and covered with mucous membrane, serves to separate the posterior nares. The anterior and inferior borders meet each other at the apex of the bone.
The vomer articulates with the sphenoid, palates, ethmoid, and maxillae, and with the triangular cartilage.
Its arteries are derived from the anterior and posterior ethmoidal, the naso-palatine, and the pterygo-palatine arteries, and twigs from the posterior palatines through Stenson's canals.
The vomer is a membrane bone, and arises from a single center deposited in the lower border of the perichondrium of the ethmo-vomerine plate as early as the eighth week. From this single center a lamina of bone extends on each side of the cartilage plate. For many weeks the vomer is a shallow bony trough. Gradually it presses upon and induces absorption of the enclosed cartilage, and by degrees the laminae fuse, and form a rectangular plate of bone. At birth the vomer presents an expanded lower border, especially in cases of cleft palate.