29 - Ear and Auditory Tube Flashcards
Name for the external ear
Auricle
Border between outer and middle ear
Tympanic membrane
Boundaries of the middle ear
Space between the tympanic membrane and petrous part of the temporal bone.
Location of the inner ear
Within the petrous part of the temporal bone
Alternative name for external auditory meatus
Ear canal
Composition of external auditory meatus
1) Lateral 1/3 is cartilagenous
2) Medial 2/3 is bony
3) Hairy skin with cerumen glands (make ear wax, prevent maceration of skin with water)
Innervation of external auditory meatus
1
2
3
1) Posterior is innervated by vagus
2) Anterior and superior is by auriculotemporal nerve (mandibular division of trigeminal nerve)
3) External surface of tympanic membrane by auriculotemporal nerve
Where can pain in tympanic membrane refer?
Inferior teeth (both innervated by auriculotemporal nerve, which branches from mandibular branch of trigeminal nerve.
Features of the surface of tympanic membrane
1) Flaccid area
2) Handle of malleus
3) Cone of light in antero-inferior quadrant.
4) Convex medially, concave laterally.
Two divisions of middle ear
1) Medial to the tympanic membrane is tympanic cavity proper
2) Superior to tympanic membrane is epitympanic recess
What does the epitympanic recess communicate with?
Mastoid air cells
Potential danger of epitympanic recess communicating with mastoid air cells
Infection of middle ear can ascend into air cells of mastoid process
Communication between tympanic cavity proper and nasopharynx
Auditory tube/Eustachian tube/pharyngotympanic tube.
Projects antreoinferiorly from tympanic cavity proper to nasopharynx
Role of Eustachian tube
Allows equalisation of pressure between nasopharynx and middle ear
Significance of antero-inferior path of Eustachian tube from middle ear to nasopharynx
1
2
1) Hard for bacteria to ascend from nasopharynx to middle ear.
2) Exudate from middle ear infection can drain into nasopharynx.
Why do infants get more middle ear infections?
Eustachian tube angle is much less inferior than adults.
Therefore easier for bacteria to ascend from nasopharynx to middle ear.
If chronic ear infections, can impair language development, as can’t hear properly.
Ossicles
Three bones that form a connection between tympanic membrane and sensory receptors in the inner ear.
Stapes
Incus
Malleus
Ossicle attached the medial surface of the tympanic membrane
Malleus