study materials

1. ANATOMY OF EAR AND
PHYSIOLOGY OF HEARING
**PRESENTED BY**
SRIDEBESH GHORUI
B.PHARM, 2ND YEAR
GURU NANAK INSTITUTE OF PHARMACEUTICAL SCIENCE AND TECHNOLOGY

2.  INTRODUCTION
 OUTER EAR
 MIDDLE EAR
 INNER EAR
 PHYSIOLOGY OF HEARING
 DISORDERS
 CONCLUSIONS
 REFERENCES
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3.  The ear is the organ of hearing and equilibrium that detects and
analyzes sound by transduction (or the conversion of sound waves into
electrochemical impulses) and maintains the sense of balance (equilibrium).
[1]
 Peripheral parts of the ear: external, middle and inner ear. These parts detect,
conduct and transform auditory signals to electrical stimuli. Signals
transmitted by the afferent auditory nerve fibres toward central nervous
system. [2]
 It convert the sound waves into nerve impulses that travel to the brain, where
they are perceived as sound. [2]
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4.  The external part of the ear, which collect sound waves and
directs them into the middle ear.
 It consists of 3 different parts –
i. Pinna.
Function: Important for sound gathering and localization of
sound
ii. Ear canal (auditory canal).
Function: Important for sound selection
iii. Eardrum.
Function: Vibrates in respond to sound. [3][4]
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6.  Irregular shaped air filled cavity within the temporal bone.
 Lateral wall of middle ear –formed by tympanic membrane.
 Roof and floor - formed by temporal bone.
 Posterior wall – formed by temporal bone with opening leading to mastoid antrum.
 Middle wall - thin layer of temporal bone.
two opening- 1- oval window
2 – round window
 Three ossicle bones – 1 – malleus, 2 – incus, 3 – stapes.
 Function : Impedance matching.
 Two muscles – 1 - stapedial muscle, 2 - tensor muscle.
 Function : Protection.
 Eustachian tube (Auditory tube).
 Function : Equalizer of air pressure. [3][4]
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7. 7

8.  It is the innermost part of the vertebrate ear.
 It contains organs of hearing and balance.
 It is described at two parts :-
1- Bony labyrinth (filled with perilymph), 2 - Membranous labyrinth( filled with
endolymph)
 Three main regions :-
i. Vestibule, ii. Three semicircular canals, iii. Cochlea.
 Vestibule:
 Expanded part near to the middle ear.
 Oval and round windows are located in it’s later wall.
 Two membranous sacs –
i. Uricle, ii.saccule
 function:- both important for maintain balance.
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9.  Three semicircular canals:-
These are 3 tubes which are situated in three planes of space.
They are attached with vestibule and also important in balance.
 Cochlea:-
This resembles a snail’s shell.
Three segments –
i. Scala vestibuli(originates in oval window)
ii.Scala media(part of membranous labyrinth)
iii. Scala tympani(ends at round window)
 On basilar membrane, supporting cells and cochlear hair cells contain auditory
receptors.
 These cells form organ of corti that respond to vibration.[3][4]
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10. 10

11. Sound wave External ear Direct sound wave to tympanic membrane
Vibration of tympanic membrane Tympanic membrane
Sound waves transfer to malleus Malleus to incus Incus to stapes
From stapes move to the oval window and perilymph (bony fluid) of scala vestibuli
Perilymph move to scala tympani displace fluid in scala media
Nerve impulses generates Stimulates auditory receptor
Impulses transmit to brain Synapse to auditory area in temporal lobe of cerebrum.
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12.  Boils : It grows in the ear canal caused by bacterial infection.
 Meniere’s Disease : It affects the inner ear.
 Otomycosis : It is the infection of the external ear canal caused by a fungus.
 Tinnitus : It characterized by a ringing in the ears, although the sound may also
be a hissing, buzzing, roaring or clicking. [3]
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13.  Ear is the organ of hearing and balance, uses resonance, impedance
matching.
 Ear can be used for both identification and verification of the sound
source.
 The diversity of therapeutic interventions for ear and hearing disorder
increases from hearing aids, personal sound amplification devices.
 Listening to degraded speech requires listeners to devote additional
resources for successful listening and understanding.
 We need to ensure that we take good care of our ears.[5]
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14. 1. Joseph E. Hawkins “Human Ear Anatomy”.
2. Dr. Szőnyi Magdolna “Ear: Anatomy and Physiology”.
3. Waugh Anne & Grant Allison “Ross and Wilson Anatomy &Physiology in Health
and Illness”, Elsevier evolve, 12 edition, chapter-8 “The special senses”, page-
192-196 & 209-210.
4. Hall John E. “Guyton & Hall Textbook of Medical Physiology: A South Asian
Edition” , Chapter-107 “Hearing”, page- 720-729.
5. Jonathan E. Peelle “Listening Effort: How the Cognitive Consequences of Acoustic
Challenge Are Reflected in Brain and Behaviour”
6. Authors: Armand Dancer.“External Ear”
7. “File:Blausen_0330_EarAnatomy_MiddleEar.png” from Blausen.com staff (2014).
Medical gallery of Blausen Medical 2014
8. “File:Blausen_0329_EarAnatomy_InternalEar.png” from Blausen.com staff
(2014). Medical gallery of Blausen Medical 2014
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15. THANK YOU
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