What are the 3 divisions of the ear and their components?
External
- auricle
- external auditory / acoustic meatus
- tympanic membrane
Middle
- ossicles (malleus, incus, stapes)
- stapedius & tensor tympani bones
- tympanic plexus
- pharyngotympanic / Eustachian tube
- mastoid antrum
Inner
- bony labyrinth
- membranous labyrinth
- vestibulococchlear organ
Describe the components of the external ear
Auricle
- fleshy part of the outer ear
- mostly fibrocartilage covered with skin, except lobe (subcutaneous tissue & skin)
- helix (upper cartilaginous curve)
- lobule
- tragus (little rounded component near EAM)
EAM
- external auditory / acoustic meatus
- 2-3cm long
- in temporal bone
- lateral 1/3 cartilage
- medial 2/3 bone
Tympanic membrane
- ear drum
- partition between external & middle ear
- thin oval membrane covered with thin skin (external) and mucus membrane (internal)
- transmits sound from EAM to ossicles
Describe the components of the middle ear
Ossicles
- 3 bones that transmit sound in a bony chain from tympanic membrane to oval window
- from lateral to medial: malleus, incus, stapes
Chorda tympani nerve
- branch of CN VII facial
tympanic plexus
- CN VII facial & CN IX glossopharyngeal
Pharyngotympanic / eustachian tube
- from middle ear to nasopharynx
- mucous membrane continuous with tympanic cavity of middle ear and nasopharynd
Mastoid antrum
- air filled extension of middle ear in mastoid process of temporal bone
Describe the components of the inner ear
Internal auditory meatus
- 1cm canal in temporal bone
- passage for CN VIII as it divides into vestibular & cochlear nerves
- passage for CN VII facial
Bony labyrinth
- vestibule, cochlea & semicircular canals
Vestibule
- small oval chamber containing utricle and saccule
- balance
Cochlea
- shell shaped opening
- sound
Semicircular canlas
- 3 fluid filled bony loops opening onto vestibule
- balance
Membranous labyrinth
- within bony labyrinth
- contains endolymph
- encloses vestibule
What are the two bones contained within the vestibule?
Saccule & utricle
What are the 3 bones contained within the middle ear?
Malleus, incus & stapes (referred to as the ossicles)
What are the components of the vestibulocochlear organ?
A bony labyrinth (outer) enclosing a membranous labyrinth (inner).
Semicircular canals opening into vestibule
Vestibule containing utricle & saccule
Cochlea containing cochlear duct
