15-1 lecture 16 sense organs ii: the ear. 15-2 basic parts of the ear external ear: hearing;...
TRANSCRIPT
15-1
Lecture 16
Sense Organs II: The Ear
15-2
Basic Parts of the Ear
• External ear: Hearing; terminates at eardrum• Middle ear: Hearing; contains auditory ossicles• Inner ear: Hearing and balance; interconnecting fluid-filled
tunnels and chambers
Fig. 19.20
15-3
External Ear• Auricle or pinna: elastic cartilage• External auditory canal• Tympanic membrane
External ear Middle ear Inner ear
Auricle(pinna) External auditory canal
Elasticcartilage
Tympanicmembrane
Fig. 19.20
15-4
Middle Ear• Auditory or
eustachian tube– Opens into
pharynx, equalizes pressure
• Ossicles: malleus, incus, stapes: transmit vibrations
• Oval window
Fig. 19.21
15-5
Inner EarLabyrinth• Bony
– Cochlea: Hearing
– Vestibule: Balance
– Semicircular canals: Balance • Membranous
Fig. 19.22
Lymphs• Endolymph
– In membranous labyrinth
• Perilymph– Space between
membranous and bony labyrinth
15-6
Structure of Cochlea• Membranous labyrinth of
cochlea– Scala vestibuli (perilymph)
– Scala tympani (perilymph)
– Cochlear duct (endolymph)
Fig. 19.27
Fig. 19.27
15-7
Structure of Cochlea• Spiral organ (organ of
Corti)– Hair cells
• Stereocilia (microvilli)
– Tectorial membrane
• Cochlear nerve
Fig. 19.27
15-8
Effect of Sound Waves on Cochlear Structures
Fig.19.28
15-9
BalanceTwo structural and functional components of balance in inner ear
1. Stationary Position and Linear Movement of HeadStationary Position and Linear Movement of Head• Evaluates position of head relative to gravity• Detects linear acceleration and deceleration• Utricle and saccule
– Maculae: Consist of hair cells embedded in statoconic membrane containing otoliths
Fig. 19.23
15-10
Vestibule in Maintaining Balance
Fig. 19.24
15-11
Balance2.2. Rotational Movements Rotational Movements
of Headof Head– Evaluates movements
of head (i.e. angular acceleration)
– 3 semicircular canals• Ampulla
– Crista ampullaris
– Hair cells
– Cupula
Vestibular nerve + Cochlear nerve = Vestibulocochlear nerve (VIII)Fig. 19.25
15-12
Crista Ampullaris and Balance
Fig. 19.26
15-13
Review QuestionA person driving a car along a straight street suddenly sees an
animal dart in front of the car. He slams on the brakes and manages to stop in time. The sensation of rapid deceleration is generated by the
(a) Bending of the microvilli of the spiral organ(b) Movement of perilymph fluid in the vestibule(c) Movement of the gelatinous covering over the maculae(d) Movement of endolymph fluid in the semicircular canals(e) Movement of the cupula
15-14
Points to Remember
• Inner ear functions for hearing and balance.• Sound waves enter the external auditory canal,
impact tympanic membrane, vibrate middle ear ossicles, strike oval window, create waves in perilymph of scala vestibuli, increase pressure in endolymph in cochlear duct, membrane supporting hair cells vibrates, hair cells stimulated, vibrations transferred to perilymph of scala tympani, travel to round window and dampened.
15-15
Points to Remember
• Static balance is orientation of body relative to pull of gravity - maculae of utricle and saccule (static labyrinth) are sense organs of static balance.
• Kinetic balance is maintenance of body position in response to movement - crista ampullaris in semicircular canals (kinetic labyrinth) are sense organs of kinetic balance.
15-16
Questions?