The ethmoid bulla (or ethmoidal bulla) is a rounded elevation upon the lateral wall of the

middle nasal 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 infer ...

(

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 nas ...

inferior to 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, ...

) produced by one or more of the underlying middle ethmoidal air cells (which open into the nasal cavity upon or superior to the ethmoidal bulla). It varies significantly based on the size of the underlying air cells.

Structure

The ethmoid bulla is formed by is the largest and least variable of the middle ethmoidal air cells. The size of the bulla varies with that of its contained cells. The bulla may be a pneumatised cell or a bony prominence found in middle meatus.

Relations

The

hiatus semilunaris The semilunar hiatus (eg, hiatus semilunaris) is a crescent-shaped/semicircular/ curved slit/groove upon the lateral wall of the nasal cavity at the middle nasal meatus just inferior to the ethmoidal bulla. It is the location of the openings for ...

is situated (sources differ) inferior/anterior to the ethmoid bulla. The

maxillary sinus The pyramid-shaped maxillary sinus (or antrum of Nathaniel Highmore (surgeon), Highmore) is the largest of the paranasal sinuses, located in the maxilla. It drains into the middle meatus of the noseHuman Anatomy, Jacobs, Elsevier, 2008, page 209- ...

also opens below the bulla.

Development

The ethmoid bulla begins to develop between 8 weeks and 12 weeks of

gestation Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pregn ...

References

Nose {{anatomy-stub Otorhinolaryngology