The semilunar hiatus or hiatus semilunaris, is a crescent-shaped groove in the lateral wall of the

nasal cavity The nasal cavity is a large, air-filled space above and behind the nose in the middle of the face. The nasal septum divides the cavity into two cavities, also known as fossae. Each cavity is the continuation of one of the two nostrils. The nasal c ...

just inferior to the

ethmoid bulla 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 ...

. It is the location of the openings of the maxillary sinuses. It is bounded inferiorly and anteriorly by the sharp concave margin of the

uncinate process of the 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 sp ...

, superiorly by the ethmoid bulla, and posteriorly by the

middle nasal concha The medial surface of the labyrinth of ethmoid consists of a thin lamella, which descends from the under surface of the cribriform plate, and ends below in a free, convoluted margin, the middle nasal concha (middle nasal turbinate). It is rough, a ...

Sinus drainage

Following the curve anteriorly leads into the infundibulum of the

frontonasal duct The frontonasal duct is a communication between the frontal air sinuses and their corresponding nasal cavity. The duct is lined by mucous membrane. The duct empties into the nasal cavity middle nasal meatus through the infundibulum of the semilun ...

, which drains the

frontal sinus The frontal sinuses are one of the four pairs of paranasal sinuses that are situated behind the brow ridges. Sinuses are mucosa-lined airspaces within the bones of the face and skull. Each opens into the anterior part of the corresponding middle na ...

. The anterior ethmoidal cells of the

ethmoidal sinus The ethmoid sinuses or ethmoid air cells of the ethmoid bone are one of the four paired paranasal sinuses. The cells are variable in both size and number in the lateral mass of each of the ethmoid bones and cannot be palpated during an extraoral ...

open into the front part of the infundibulum as well. In slightly over 50% of subjects, this is directly continuous with the frontonasal duct from the

frontal air sinus The frontal sinuses are one of the four pairs of paranasal sinuses that are situated behind the brow ridges. Sinuses are mucosa-lined airspaces within the bones of the face and skull. Each opens into the anterior part of the corresponding middle ...

. When the anterior end of the uncinate process fuses with the front part of the bulla, however, this continuity is interrupted and the frontonasal duct then drains directly into the anterior end of the

middle meatus In anatomy, the term nasal meatus can refer to any of the three meatuses (passages) through the skulls nasal cavity: the superior meatus (''meatus nasi superior''), middle meatus (''meatus nasi medius''), and inferior meatus (''meatus nasi inferio ...

. The ostium for 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 ...

opens posteriorly in this groove and is the largest ostium within the semilunar hiatus.

References

External links

* {{Authority control Nose