Keskikorvaa

Keskikorva, or middle ear, is an air-filled cavity in the temporal bone that lies between the outer ear and the inner ear. It forms the first part of the auditory pathway and plays a central role in the transmission of sound from the eardrum to the inner ear.

Anatomy and connections: The middle ear contains three auditory ossicles—the malleus (hammer), incus (anvil), and stapes (stirrup)—housed within the tympanic cavity. The tympanic membrane forms the lateral boundary, and the oval window on the medial wall connects to the inner ear. The aditus to the mastoid air cell system links the middle ear to mastoid air cells. The Eustachian tube opens into the middle ear and helps equalize pressure with the nasopharynx.

Function: The tympanic membrane vibrates in response to sound; these vibrations are transmitted and amplified by the ossicles, culminating in movement of the oval window and fluid motion within the cochlea. The muscles tensor tympani and stapedius can dampen vibrations in response to loud sounds (the acoustic reflex) to protect the inner ear.

Nerve supply and development: The middle ear receives sensory input via the tympanic plexus, while motor innervation to the stapedius is provided by the facial nerve (CN VII). Embryologically, the malleus and incus arise from the first pharyngeal arch, while the stapes largely derives from the second arch.

Clinical relevance: The middle ear is susceptible to infections and effusions (otitis media), otosclerosis (stiffening of the stapes), and cholesteatoma. Standard treatments include antibiotics, myringotomy, tympanoplasty, and, when appropriate, stapedectomy.