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 ...
just inferior to the
ethmoid bulla. 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, 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 ...
.
Sinus drainage
Following the curve anteriorly leads into the infundibulum of the
frontonasal duct, 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 midd ...
.
The
anterior ethmoidal cells of the
ethmoidal sinus 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. 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 inferi ...
.
The ostium for the
maxillary sinus
The pyramid-shaped maxillary sinus (or antrum of Nathaniel Highmore (surgeon), 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, ...
opens posteriorly in this groove and is the largest ostium within the semilunar hiatus.
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