Corpus: Middle ear
1. Definition
The paired middle ear is the air-filled space between the eardrum and the inner ear in the petrous portion of temporal bone. It contains the tympanic cavity (cavum tympani) with the 3 auditory ossicles, which transmit and amplify sound to the cochlea. The middle ear is connected to the nasopharynx via the auditory tube.
2. Anatomy
2.1. Overview
The largest part of the middle ear is occupied by the tympanic cavity. It is a pneumatised cavity within the petrous portion of temporal bone. The middle ear is lined with a mucous membrane consisting of a single-layer epithelium. Inside the middle ear are the three auditory ossicles, which belong to the sound conduction system:
They connect the eardrum to the oval window (fenestra ovalis). The middle ear is connected to the nasopharynx via the auditory tube (Eustachian tube). The tympanic cavity also communicates with the air-filled cavities of the petrous portion and mastoid process of temporal bone.
In addition to the auditory ossicles, the middle ear muscles (Musculi ossiculorum auditus) are found in the tympanic cavity:
- Tympanic muscle: stretches the eardrum
- Stapedius muscle: tilts the stapes
2.2. Pathways
The middle ear contains numerous pathways that supply the local structures or pass through the tympanic cavity to other supply areas. These include, among others:
3. Physiology
The articulated bones of the middle ear allow the sound waves hitting the eardrum to be transmitted to the cochlea with as little loss as possible. The middle ear thus functions as a mechanical "impedance transducer".
4. Clinic
- Ear barotrauma
- Secretory otitis media
- Middle ear inflammation (otitis media)
- Inflammation of the eardrum (myringitis)
- Rupture or perforation of the eardrum