Tympanic bulla
Bulla tympanica
Definition
The tympanic bulla is a smooth bulbous enlargements of the tympanic part of the temporal bone*. It lies between the retroarticular and paracondylar processes.
The tympanic bulla encloses the fundic apart of the tympanic cavity, which is delimited from the dorsal part of tympanic cavity proper by a thin edged of bone, the septum bullae.
The development of tympanic bulla varies between species:
In men, it is absent.
In equidae and ruminants, it is small or absent.
In pigs, it is very developed.
In bulls, even more and stretched dorsoventrally.
In carnivorous and glires, it is great and rounded, hence its name.
*The tympanic bulla belongs to the tympanic part of the temporal bone in most of species, but in cats, the larger medial part of the tympanic bulla is formed by the endotympanic part of the temporal bone.
References
Text by Antoine Micheau, MD - Copyright IMAIOS
