Ethmoid bulla

The ethmoid bulla is a rounded elevation upon the lateral wall of the middle [nasal meatus]' produced by one or more of the underlying middle ethmoidal air cells.' 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 is situated inferior/anterior to the ethmoid bulla. The maxillary sinus also opens below the bulla.

Development

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