Trumhåla

Trumhåla, or tympanic cavity, is an air-filled space within the temporal bone that forms part of the middle ear. It lies medial to the tympanic membrane and lateral to the inner ear, and it functions as a conduit for sound from the eardrum to the inner ear. The cavity communicates with the nasopharynx through the auditory (Eustachian) tube and with the mastoid air cell system via the aditus to the mastoid antrum.

Anatomically, the tympanic cavity is divided into two main regions: the tympanic cavity proper and the epitympanic recess (attic) located above the level of the tympanic membrane. The lateral wall is the tympanic membrane, while the medial wall houses the promontory, the oval window, and the round window. The posterior wall contains the aditus and connects to the mastoid antrum, and the roof (tegmen tympani) separates it from the cranial cavity.

The cavity contains the auditory ossicles—the malleus (hammer), incus (anvil), and stapes (stirrup)—which form the chain transferring vibrations from the eardrum to the inner ear. The tensor tympani muscle attaches to the malleus, and the stapedius muscle attaches to the stapes; both muscles help dampen loud sounds and protect the inner ear.

Innervation of the tympanic cavity mucosa is provided by the tympanic plexus, formed in part by tympanic branches of the glossopharyngeal nerve (CN IX), with parasympathetic fibers reaching the mucosa via the lesser petrosal nerve. Blood supply comes from branches of the maxillary and posterior auricular arteries, including the anterior tympanic and related arteries.

Clinically, the tympanic cavity is central to otitis media and other middle-ear disorders, which can affect hearing and balance. Conditions such as effusion, cholesteatoma, or ossicular disruption reflect disease processes within this space.