Summary The Ear

STRUCTURE: -
-
Middle ear is connected to pharynx by Eustachian tube.
FUNCTIONS:
Pinna
 Tympanic membrane transmits sound waves to ossicles
 Ossicles transmit vibrations from tympanic membrane to inner
ear
 Eustachian tube maintains equal pressure on either side of ear
Auditory nerve drum.
 Oval window transmits vibrations of ossicles to inner ear.
 Round window absorbs pressure set up in inner ear.

 INNER EAR
- Fluid-filled cavity made up of bony labyrinth & membranous labyrinth.
- Bony labyrinth → filled with perilymph
- Membranous labyrinth → made of membranous sacs & tubes that float
around in the perilymph (semi-circular canals; sacculus; cochlea); filled
 OUTER EAR with endolymph
- Cartilaginous pinna → directs sound waves through auditory canal - Membranous cochlea (within bony cochlea) has 3 canals:
towards tympanic membrane) o Upper canal (filled with perilymph)
- Auditory canal → conducts sound waves to tympanic membrane; cerumen o Middle canal (filled with endolymph)
/ wax & hairs found in it prevent entrance of small organisms; wax o Lower canal (filled with perilymph)
prevents drying out of ear drum. - FUNCTIONS:
 Semi-circular canals, sacculus & utriculus → concerned with
 MIDDLE EAR balance & equilibrium of the body.
- Air-filled cavity within the skull, separated from outer ear by tympanic  Cochlea contains organ of Corti → converts stimulus of sound
membrane & separated from inner ear by oval window and round window. into an impulse.
- 3 bones (ossicles) → hammer (malleus); anvil (incus) & stirrup (stapes).  Auditory nerve arising from cochlea transmits sound impulse to
- Hammer is attached to tympanic membrane; stirrup is attached to oval brain.
window & anvil lies between hammer & stirrup.