Below the

bulla ethmoidalis The ethmoid bulla (or ethmoidal bulla) is an elevation on the lateral wall of the middle meatus of the nose. It is produced by middle ethmoidal cells. It develops during the first trimester of gestation, and varies significantly based on the size ...

, and partly hidden by the inferior end of the

uncinate process of ethmoid bone In the ethmoid bone, a sickle shaped projection, the uncinate process, projects posteroinferiorly from the ethmoid labyrinth. Between the posterior edge of this process and the anterior surface of the ethmoid bulla, there is a two-dimensional s ...

, is the maxillary hiatus (or ostium maxillare, or maxillary sinus ostium, or maxillary ostium, or opening from the

maxillary sinus The pyramid-shaped maxillary sinus (or antrum of Highmore) is the largest of the paranasal sinuses, and drains into the middle meatus of the nose through the osteomeatal complex.Human Anatomy, Jacobs, Elsevier, 2008, page 209-210 Structure It is ...

); in a frontal section this opening is seen to be placed near the roof of the

sinus Sinus may refer to: Anatomy * Sinus (anatomy), a sac or cavity in any organ or tissue ** Paranasal sinuses, air cavities in the cranial bones, especially those near the nose, including: *** Maxillary sinus, is the largest of the paranasal sinuses, ...

. In the articulated skull this aperture is much reduced in size by the following bones: the uncinate process of the ethmoid above, the ethmoidal process of the inferior nasal concha below, the vertical part of the palatine behind, and a small part of the lacrimal above and in front; the sinus communicates with the middle meatus of the nose, generally by two small apertures left between the above-mentioned bones.

Additional images

File:Siebbein1.jpg, Ethmoid bone

References

Nose {{musculoskeletal-stub