2015 Hearing & Balance

Middle ear

Middle ear space EMOssicles
http://www.proscan.com
  • the middle ear consists of an extensive air-filled space in the temporal bone called the tympanic cavity

  • the tympanic cavity is ventilated by the auditory (Eustachian) tube, which connects to pharynx
    • the bony portion of the tube (closest to the middle ear) is covered by low columnar epithelium with cilia
    • the cartilaginous portion of the tube is composed of pseudostratified epithelium overlying elastic cartilage

  • the purpose of the auditory tube is to keep the air pressure in the middle ear space equal to the pressure in the external ear canal, which allows the tympanic membrane and the ossicles to vibrate freely
    • pressure differentials (e.g. by changing altitude quickly) can compress or loosen the joints between the ossicles; both conditions reduce middle ear efficiency (conductive hearing loss)
    • changes in pressure can also stimulate nociceptors in the tympanic membrane, resulting in pain
  • there are 3 middle ear bones (ossicles) suspended in the attic of the middle ear space

  • the manubrium = handle of the malleus (1) is embedded in the tympanic membrane, ending at the umbo

  • the head of the malleus (4) connects to the incus (6)

  • the malleus and incus are suspended by two ligaments that provide an axis of rotation (2 and 7) so that the middle ear bones pivot when the tympanic membrane vibrates

  • the footplate of the stapes (15) inserts into the oval window of the inner ear
Email: Dr. Janet Fitzakerley | ©2015 University of Minnesota Medical School Duluth | Last modified: 15-feb-15 3:42 PM