Human Ear Anatomy

Study Notes

The ear is responsible for hearing and maintaining balance (equilibrium) of the body.
The ear is divided into three parts: external ear, middle ear, and internal ear.

The external ear consists of the auricle and external auditory meatus.
The auricle projects from the side of the head, with a lower fleshy part called the lobule (containing no cartilage).
The concha is a central depression in the auricle.
The external auditory meatus is an S-shaped tube, 24 mm in length, extending from the concha to the tympanic membrane.
The outer part of the meatus is cartilaginous and directed upwards, backwards, and medially, while the inner part is bony and directed downwards, forwards, and medially.
The nerve supply to the external ear comes from the auriculotemporal nerve and auricular branch of vagus.

The tympanic membrane is an oval, semitransparent membrane forming the lateral boundary of the middle ear.
The lateral surface of the membrane is concave, while the medial surface is convex and receives the attachment of the malleus.
The nerve supply to the tympanic membrane comes from the auriculotemporal nerve and auricular branch of vagus (lateral surface) and the tympanic plexus (medial surface).

The middle ear (tympanic cavity) is a narrow, air-filled cavity within the petrous part of the temporal bone.
The middle ear contains air, auditory ossicles (malleus, incus, and stapes), auditory muscles (tensor tympani and stapedius), nerves (chorda tympani and tympanic branch of glossopharyngeal nerve), and blood vessels.
The boundaries of the middle ear include the tegmen tympani (roof), the floor (separating the tympanic cavity from the jugular bulb), and the anterior, posterior, lateral, and medial walls.
The nerve supply to the middle ear comes from the tympanic plexus.

The tensor tympani muscle tenses the tympanic membrane and is supplied by the mandibular nerve.
The stapedius muscle draws the stapes laterally and is supplied by the facial nerve.
The two muscles lessen transmission of sound vibrations as a protective mechanism against sounds of higher intensity.