Septum bullae
Septum bullae
Definition
The septum bullae is a thin edged of bone that delimits the fundic part of the tympanic cavity (formed by the tympanic bulla) from the dorsal part of tympanic cavity proper.
The septum bullae varies between different species:
In felidae, the septum bullae is formed by the tympanic part and the endotympanic part of the temporal bone.
In the dog, the bulla septum is a small, incomplete ridge that only makes contact with the petrous portion of the temporal bone rostrally and often has tiny, elongate bony spicules with bulbous ends.
In the cat, the septum bulla abuts the petrous portion of the temporal bone and separates the tympanic cavity into two compartments: the dorsolateral epitympanic cavity (pars tympanica) and the ventromedial tympanic cavity (pars endotympanica). This separation is almost complete, allowing communication between the two compartments only through two small openings: one is between the septum bulla and petrous portion of the temporal bone and the other is located caudally, just lateral to the round window.
The difference in the size of this septum between the dog and the cat is of clinical significance in the treatment and management of middle ear disease.
References
Text by Antoine Micheau, MD - Copyright IMAIOS
Njaa, Brad & Cole, Lynette & Tabacca, Natalie. (2012). Practical Otic Anatomy and Physiology of the Dog and Cat. Veterinary Clinics of North America Small Animal Practice. 42. 1109-26. 10.1016/j.cvsm.2012.08.011.
