Have you

heard the news???

It’s

ear time!!

Trivia QuestionTrivia QuestionWhat are the smallest bones What are the smallest bones

in the body?in the body?OssiclesOssicles

OssiclesOssiclesThese bones are fully developed at These bones are fully developed at

birth!birth!

How the Ear Works!AHow the Ear Works!An Animation!!n Animation!!

Ear has 2 main functionsEar has 2 main functionsHearingHearingEquilibriumEquilibrium–StaticStatic–DynamicDynamic

Eustachian Tube

The EarThe Ear

StructureStructureEar has three main Ear has three main sectionssections–Outer earOuter ear–Middle earMiddle ear–Inner earInner ear

Outer EarOuter Ear PinnaPinna

– Ear flapEar flap– Collects sound wavesCollects sound waves– Directs them to the…Directs them to the…

Auditory canalAuditory canal– Carries sound to the eardrumCarries sound to the eardrum– Protects earProtects ear

Ear wax – made by Ear wax – made by specialized sweat glandsspecialized sweat glands

Traps foreign particlesTraps foreign particles

Middle EarMiddle Ear Begins at ear drum (tympanic Begins at ear drum (tympanic

membrane)membrane) Air filledAir filled Contains Contains ossiclesossicles

– Hammer (malleus)Hammer (malleus)– Anvil (incus)Anvil (incus)– Stirrup (stapes)Stirrup (stapes)

Strikes oval windowStrikes oval window Oval window much smaller than Oval window much smaller than tympanic membrane – helps amplify tympanic membrane – helps amplify soundsound

Eustachian tubeEustachian tube–Connects middle ear Connects middle ear with nose and mouthwith nose and mouth

–Allows for Allows for equalization of equalization of air air pressurepressure

Inner EarInner Ear

Inner EarInner Ear 3 main structures3 main structures

1. Vestibule1. Vestibule Contains 2 sacs – utricle and Contains 2 sacs – utricle and sacculesaccule

Contains fluid, hair cells, Contains fluid, hair cells, and Otoliths and Otoliths CaCO CaCO33 (s) (s)Stimulate nerve fibresStimulate nerve fibres

Detects head position Detects head position –Static equilibriumStatic equilibrium

Semicircular Canals

2. Semicircular canals2. Semicircular canals Fluid filledFluid filled 3 canals3 canals

–Horizontal, vertical, Horizontal, vertical, diagonaldiagonal

movement & balancemovement & balance Each canal has an Each canal has an ampullaampulla– cilia cilia receptor cells receptor cells

Dynamic equilibriumDynamic equilibrium

Equilibrium and Balance

Hearing

3. Cochlea3. Cochlea Liquid filledLiquid filled Vibrations Vibrations waves waves

Converted to nerve impulsesConverted to nerve impulses 3 sections3 sections

Cochlear ductCochlear duct contains contains organ of cortiorgan of corti with with ciliacilia

Scala tympaniScala tympani (tympanic canal) (tympanic canal) Scala VestibuliScala Vestibuli (vestibular canal) (vestibular canal)

An Unwound Cochlea

Outer Middle Inner

Organ OfCorti

Scala vestibuli

Scala tympani

Basilar membrane

Tectorial mem

Cochlear duct

Organ of CortiOrgan of Corti– Contains cilia which stimulate nervesContains cilia which stimulate nerves– Cilia attached to cells in the basilar Cilia attached to cells in the basilar

(bottom) membrane and touch the (bottom) membrane and touch the tectorial membrane (top membrane)tectorial membrane (top membrane)

– Sensory Hair cells – respond to Sensory Hair cells – respond to vibration of basilar membranevibration of basilar membrane

– An An action potentialaction potential develops in develops in sensory nervessensory nerves

– Sending auditory info to brain Sending auditory info to brain (temporal lobe)(temporal lobe)

BasilarMembrane

TectorialMembrane

Cilia

Organ of CortiOrgan of Corti

Cochlea and Cortex of Cerebrum

Pitch and Pitch and LoudnessLoudness

Stimulation of cells in different Stimulation of cells in different areas cause different pitchesareas cause different pitches

Cochlea narrow in beginningCochlea narrow in beginning– Hair fibers very rigidHair fibers very rigid– Responding to high frequencyResponding to high frequency– Basilar membrane vibratesBasilar membrane vibrates– Sound dies fastSound dies fast

Cochlea eventually gets widerCochlea eventually gets wider– Hair fibers more elasticHair fibers more elastic– Responding to low freqResponding to low freq– Sound resonates (lasts longer)Sound resonates (lasts longer)

3 Parts of Ear3 Parts of Ear

Outer Middle InnerAir Air Fluid

Pinna Tympanic Membrane

Semicircular Canals

Auditory Canal

OssiclesH, A, S

Vestibule

Tympanic Membrane

Eustachian Tube

CochleaOrgan of Corti