1. Auricle/Pinnae – funnel-like structure that helps collect sound waves 2. External Acoustic Meatus (EAM)/external auditory canal – s – shaped tube that extends inward 2.5 cm > leads to temporal bone > changes sound wave pressure 3. Eardrum (tympanic membrane) – semitransparent membrane covered by a thin layer of skin on outer-surface & mucous membrane on inside

Air-filled space in temporal bone 3 small ear bones called auditory ossicles: (malleus (hammer) > incus (anvil) > stapes (stirrups) The malleus is attached to the eardrum and the vibration travels in that order…each bone passing vibration on to the next Ossicles help amplify (increase) the force of vibrations as they pass from the ear drum to the oval window

Auditory tube (eustachian tube) – connects middle ear to throat > helps maintain equal air pressure for normal hearing Oval Window – leads into the inner ear – vibration of the stapes at the oval window moves a fluid within the inner ear, that stimulates hearing receptors

Complex system of communicating chambers & tubes called labyrinth 2 parts of labyrinth: 1. Osseous labyrinth – bony canal in temporal bone and secretes perilymph fluid 2. Membranous labyrinth – tube that lies within the osseous and contains endolymph fluid Labyrinths include 3 semicircular canals (sense equilibrium) & a cochlea (function in hearing)

Bony core & thin, bony shelf that winds around the core like threads of a screw Sense of hearing Scala vestibuli – upper compartment Scala tympani – lower compartment Cochlear duct – portion of membranous labyrinth Organ of Corti (spiral organ) – has hearing receptors (hair cells)

Round Window – a membrane covered opening in the wall of the inner ear – sends vibrations into tympanic cavity Vestibulocochlear Nerve: Vestibular branch – contain receptors involved with reflexes that help maintain equilibrium (balance) Cochlear branch – contain hearing receptors Vestibule – bony chamber between the semicircular canals and the cochlea – organs of static equilibrium are located here (maintain balance when body is still)  Contains 2 expanded chambers – a utricle and a saccule that have many hair cells that serve as sensory receptors