Maxillary sinus

The maxillary sinus (Sinus maxillaris) is carved within the maxilla but can extend to the palatine bone, the lacrymal bone, the zygomatic bone and annex dependancies of the ventral nasal conchae or of the sphenoidal sinus.

It is located rostrolaterally to the orbit and presents a remarkable relation with the infra-orbital duct, that follows it or passes through it back to front.as well as with the alveoli of the molar teeth.

The conformation and topography of the maxillary sinus, as well as the disposition of the sinusonasal orifice present great specific and individual variations. Carved inside the body of the maxillary bone, it is also partially demilited by the lacrymal bone and medially by the orbital plate of the ethmoid bone. The ablation of these two bones leaves on the isolated maxilla a gaping opening called maxillary hiatus (Hiatus maxillare). In certain species (Equidae, Ruminants), the infra-orbital canal is enclosed inside a more or less important bony plate that protrudes inside the sinus and tends to subdivide the sinus into a medial and a lateral compartments.

The Horse presents a remarkable particularity: an imperforated transverse wall completely divides its maxillary sinus into a rostral maxillary sinus (Sinus maxillaris rostralis) and a caudal maxillary sinus (Sinus maxillaris caudalis).