BIOL 2401 Unit 4 Lab Human Ear Study

BIOL 2401 Unit 4 Lab Human Ear Study Guide Use this study guide to review the structures of the human ear for Lab Exam 4 Information in this study guide corresponds to the information in the lab-exam review

Overview of the Human Ear The human ear is composed of structures in the external (outer) ear, middle ear, and internal (inner) ear. Frontal view of right ear shown External (outer) ear: • Pinna auditory • External auditory canal inner ear ossicles • Tympanic membrane Middle ear: • Auditory ossicles • Eustachian tube • Stapedius muscle (not shown) • Tensor tympani muscle (not shown) Internal (inner) ear: • Bony labyrinth pinna external auditory canal tympanic membrane – – Eustachian tube • Ampulla Cochlea Semicircular canals Vestibule (not shown) Membranous labyrinth – Ampulla (not shown) – Semicircular ducts – Utricle & saccule (not shown)

External (Outer) Ear Lateral view of right ear shown helix • Pinna – Functions to direct soundwaves into the external auditory canal antihelix – Regions of pinna: Helix Antihelix Lobule external auditory canal pinna lobule • External auditory canal

External (Outer) & Middle Ear Frontal view of right ear shown External (outer) ear: • External auditory canal tympanic membrane – Functions to allow soundwaves to enter ear and strike the tympanic membrane tensor tympani muscle • Tympanic membrane – Functions to vibrate when stimulated by soundwaves and causes auditory ossicles to vibrate Middle ear: • Eustachian tube – Functions to allow air pressure to equalize in the middle ear • external auditory canal Eustachian tube Tensor tympani muscle – Functions to limit the movement and increase tension of the tympanic membrane

Middle Ear Frontal view of right ear shown incus • Auditory ossicles (bones in middle ear) – Malleus – Incus – Stapes (not shown) – Function to vibrate to transmit soundwaves into the internal (inner) ear • Eustachian tube malleus Eustachian tube

Internal (Inner) Ear Frontal view of right ear shown lateral semicircular duct posterior semicircular canal • anterior semicircular duct (clear tube) • Functions in hearing endolymph (clear tube) Bony labyrinth – Ampullae – Cochlea – Semicircular canals (orange fluid) • Function in dynamic equilibrium • Anterior, lateral, & posterior – Perilymph (not shown) • Fluid inside bony labyrinth • bony ampullae cochlea Membranous labyrinth – Ampullae (not shown) – Semicircular ducts • Function in dynamic equilibrium • Anterior, lateral, & posterior – Endolymph • Fluid inside membranous labyrinth

Internal (Inner) Ear Lateral view of right inner ear shown endolymph (orange fluid) anterior semicircular duct (clear tube) • lateral semicircular duct (clear tube) Bony labyrinth – Ampullae – Cochlea – Semicircular canals • Anterior, lateral, & posterior – Perilymph (not shown) cochlea • Fluid inside bony labyrinth • Membranous labyrinth – Ampullae (not shown) – Semicircular ducts • Anterior, lateral, & posterior – Endolymph • Fluid inside membranous labyrinth • stapes posterior semicircular canal bony ampulla stapedius muscle • Auditory ossicles – Malleus (not shown) – Incus (not shown) – Stapes Stapedius muscle – Functions to limit the movement of the stapes to protect the oval window

Internal (Inner) Ear anterior semicircular canal Anterior view of left inner ear shown bony ampulla anterior semicircular duct • posterior semicircular canal Bony labyrinth – Ampullae – Cochlea – Semicircular canals • Anterior, lateral, & posterior membranous ampulla – Vestibule • Functions in static equilibrium – Perilymph (not shown) utricle • Fluid inside bony labyrinth • Membranous labyrinth – Ampullae – Semicircular ducts • Anterior, lateral, & posterior lateral semicircular canal • Functions in static equilibrium – Endolymph (not shown) oval window cochlea – Utricle & saccule (inside vestibule) • Fluid inside membranous labyrinth vestibule • Oval window

Internal (Inner) Ear Inferior view of left inner ear shown oval window (stapes removed) • Bony labyrinth – Ampullae bony ampulla – Vestibule • Oval window – Covered by stapes vestibule • round window Round window

Internal (Inner) Ear Superior & posterior view of left inner ear shown anterior semicircular canal • lateral semicircular canal – Ampullae – Cochlea anterior semicircular duct perilymph Bony labyrinth – Semicircular canals • Anterior, lateral, & posterior membranous ampulla – Vestibule – Perilymph utricle saccule • Fluid inside bony labyrinth • Membranous labyrinth – Ampullae – Semicircular ducts • Anterior, lateral, & posterior – Utricle & saccule (inside vestibule) – Endolymph (not shown) posterior semicircular canal bony ampulla cochlea • Fluid inside membranous labyrinth

Internal (Inner) Ear Posterior view of left inner ear shown • anterior semicircular canal – Ampullae – Cochlea anterior semicircular duct lateral semicircular canal perilymph Bony labyrinth – Semicircular canals • Anterior, lateral, & posterior utricle – Vestibule – Perilymph saccule • Fluid inside bony labyrinth • Membranous labyrinth – Ampullae (not shown) – Semicircular ducts • Anterior, lateral, & posterior – Utricle & saccule (inside vestibule) – Endolymph (not shown) posterior semicircular canal bony ampulla vestibule cochlea • Fluid inside membranous labyrinth

Internal (Inner) Ear Medial view of inner ear shown anterior semicircular canal • Bony labyrinth – Ampullae – Semicircular canals • Anterior, lateral, & posterior perilymph – Vestibule (not shown) anterior semicircular duct – Perilymph • Fluid inside bony labyrinth • Membranous labyrinth – Ampullae – Semicircular ducts membranous ampulla utricle • Anterior, lateral, & posterior – Utricle & saccule (inside vestibule) – Endolymph (not shown) • Fluid inside membranous labyrinth saccule bony ampulla

Cochlea Frontal view (cross-section) of cochlea shown vestibular membrane scala vestibuli • Bony labyrinth – Scala vestibuli (vestibular duct) • Contains perilymph scala media – Scala tympani (tympanic duct) • Contains perilymph • Membranous labyrinth tectorial membrane – Scala media (cochlear duct) • Contains endolymph • Basilar membrane hair cells scala tympani • Vestibular membrane Organ of Corti: • Hair cells – Function to detect & transduce mechanical stimuli (fluid pressure waves) into action potentials basilar membrane • Tectorial membrane

Cochlea & Organ of Corti Frontal view of cochlea & organ of Corti shown scala vestibuli tectorial membrane • Bony labyrinth vestibular membrane – Scala vestibuli (vestibular duct) • Contains perilymph – Scala tympani (tympanic duct) scala media • Contains perilymph • Membranous labyrinth – Scala media (cochlear duct) • Contains endolymph • Basilar membrane • Vestibular membrane Organ of Corti: scala tympani basilar membrane hair cells • Hair cells • Tectorial membrane