The mastoid antrum (tympanic antrum, antrum mastoideum, Valsalva's antrum) is an air space in the petrous portion of the

temporal bone The temporal bones are situated at the sides and base of the skull, and lateral to the temporal lobes of the cerebral cortex. The temporal bones are overlaid by the sides of the head known as the temples, and house the structures of the ears. Th ...

, communicating posteriorly with the

mastoid cells The mastoid cells (also called air cells of Lenoir or mastoid cells of Lenoir) are air-filled cavities within the mastoid process of the temporal bone of the cranium. The mastoid cells are a form of skeletal pneumaticity. Infection in these cells ...

and anteriorly with the

epitympanic recess The epitympanic recess is a hollow located on the superior/roof aspect of the middle ear. Clinical significance This recess is a possible route of spread of infection to the mastoid air cells located in the mastoid process of the temporal bone ...

of the

middle ear The middle ear is the portion of the ear medial to the eardrum, and distal to the oval window of the cochlea (of the inner ear). The mammalian middle ear contains three ossicles, which transfer the vibrations of the eardrum into waves in the ...

via the

aditus to mastoid antrum The aditus to mastoid antrum (otomastoid foramen or entrance or aperture to the mastoid antrum) is a large irregular cavity that leads backward from the epitympanic recess into a considerable air space named the tympanic or mastoid antrum. The a ...

(entrance to the mastoid antrum). These air spaces function as sound receptors, provide voice resonance, act as acoustic insulation and dissipation, provide protection from physical damage and reduce the mass of the cranium. The roof is formed by the tegmen antri which is a continuation of the

tegmen tympani The tympanic cavity is a small cavity surrounding the bones of the middle ear. Within it sit the ossicles, three small bones that transmit vibrations used in the detection of sound. Structure On its lateral surface, it abuts the external auditor ...

and separates it from the

middle cranial fossa The middle cranial fossa, deeper than the anterior cranial fossa, is narrow medially and widens laterally to the sides of the skull. It is separated from the posterior fossa by the clivus and the petrous crest. It is bounded in front by the pos ...

. The lateral wall of the antrum is formed by a plate of bone which is an average of 1.5 cm in adults. The

mastoid air cell The mastoid cells (also called air cells of Lenoir or mastoid cells of Lenoir) are air-filled cavities within the mastoid process of the temporal bone of the cranium. The mastoid cells are a form of skeletal pneumaticity. Infection in these cells ...

system is a major contributor to middle ear inflammatory diseases.

Additional images

File:Gray1209.png, Left

showing surface markings for the tympanic antrum (red), transverse sinus (blue), and

facial nerve The facial nerve, also known as the seventh cranial nerve, cranial nerve VII, or simply CN VII, is a cranial nerve that emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of tas ...

(yellow).

References

External links

* - "Illustration of the continuity of the nasopharynx with the middle ear cavity via the auditory tube." {{Authority control Bones of the head and neck Ear