THE HUMAN EAR
By
TEHREEM IJAZ
MS(SLP), PGD-SLP, MSc (Applied Psychology)
tehreem.ijaz@riphah.edu.pk
RIPHAH COLLEGE OF REHABILITATION SCIENCES
 The ears are paired sensory organs comprising the
auditory system, involved in the detection of sound, and
the vestibular system, involved with maintaining body
balance/ equilibrium.
Ear
 The ear is an energy transducer, which
means that it converts acoustic energy into
electrochemical energy.
Ear
 The ear divides anatomically and functionally into three
regions:
 the external ear,
 the middle ear, and
 the inner ear.
 All three regions are involved in hearing. Only the inner ear
functions also in the vestibular system.
HOW THE EAR WORKS
 Ears are extraordinary organs.
 They pick up all the sounds around you and then translate this information
into a form your brain can understand.
 One of the most remarkable things about this process is that it is
completely mechanical.
Major Divisions of the Ear
Peripheral Mechanism
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Outer Middle Inner
Cranial
Ear
Ear
Ear
Nerve
Central
Mechanism
Brain
Main Components of the Hearing
Mechanism:
Divided into 4 parts (by function):
 Outer Ear
 Middle Ear
 Inner Ear
 Central Auditory Nervous System
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Outer Ear
Pinna
External
Auditory
Meatus
Tympanic
membrane
EXTERNAL EAR
 Auricle (pinna) flap of
elastic cartilage
 External auditory canal
 Tympanic membrane
Pinna
Pinna
 The visible portion that
is commonly referred to
as "the ear"
Function of Outer Ear
 Collect sound
 Localization
 Resonator
 Protection
 Sensitive (earlobe)
External Auditory Meatus
 Extends from the pinna to the tympanic membrane
 About 24 millimeters (mm) in length and 7 mm in diameter in
adult ear.
 Size and shape vary among individuals.
 Its not a straight tube
 Its outer part is directed upwards, backward and medially
 Inner part is directed downward, forward and medially.
 To see the tympanic membrane, the pinna has to be pulled
upward, backward and laterally to bring two parts alignment.
 Protects the eardrum
 Resonator
External Auditory Meatus
 The net effect of the pinna, and ear canal is that
sounds are amplified.
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Parts of External Auditory
Meatus
 The canal is divided in to two parts.
1. Cartilaginous part
2. Bony part
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Cartilaginous part: it forms outer one-third(8mm) of the canal.
Cartilage is a continuation of the cartilage which forms the
framework of the pinna.
 The skin, covering the cartilaginous canal is thick and contains
ceruminous and sebaceous glands which secrete wax.
 Hair is only confined to the outer canal and therefore hair
follicles are seen only in the outer one third of the canal.
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Bony Part: It forms inner two-third(16mm) of the canal. The Skin
lining the bony canal is thin and continuous over the tympanic
membrane. It is devoid of hair and ceruminous glands.
 About 6mm lateral to tympanic membrane, the bony meatus
presents a narrowing called the isthmus.
 Foreign bodies lodged medial to the isthmus, get impacted and
are difficult to remove.
 Anterioinferior part of the deep meatus, beyond the isthmus,
presents the recess called the anterior recess which acts as a
cesspool for discharge and debris in cases of external and middle
ear infections.
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Cerumen
 The purpose of wax:
 Repel water
 Trap dust, sand particles, micro-organisms, and other
debris
 Moisturize epithelium in ear canal
 Odor discourages insects
 Antibiotic, antiviral, antifungal properties
 Cleans ear canal
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Tympanic Membrane
 It forms the partition between the external acoustic canal
and the middle ear.
 It is obliquely set and as a result, its postero-superior part is
more lateral than its antero-inferior part.
 It is 9-10mm tall, 8-9 mm wide and 0.1mm thick
 The eardrum vibrates in response to sound pressure waves.
 The membrane movement is incredibly small
 as little as one-billionth of a centimeter
 It is divided into two parts.
1. Pars Tensa
2. Pars Flaccida
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Pars Tensa: It forms most of the tympanic membrane,
 Its periphery is thickened to form a fibro cartilaginous ring
called as annulus tympanicus, which fits into tympanic
sulcus.
 The central part of parstensa, is tented inwards at the level
of the tip of the malleus and is called the umbo.
 A bright cone of light can be seen radiating from the tip of
malleus to the periphery in the anteroinferior quadrant.
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 Pars Flaccida: this is situated above the lateral process
of malleus between the notch of rivinus and the
anterior and posterior mallel folds.
 It appears slightly pinkish.
Tympanic Membrane
(eardrum)
1 – umbo;
2 - handle of malleus;
(3) (6) anterior and
posterior
malleus folds;
4 - Pars flaccida
5 - short process of
malleus;
7 – pars tensa;
8 – cone of light
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Tympanic membrane
The tympanic membrane consists of three layers.
 The outer layer of skin is continuous with that of the
external canal.
 The inner layer of mucous membrane is continuous with
the lining of the tympanic cavity of the middle ear.
 Between these layers is a layer of fibrous tissue made up of
circular and radial fibres that give the membrane its
stiffness and tension.
The membrane is well supplied with blood vessels and
sensory nerve fibres that make it acutely sensitive to pain.
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Relations
 Superiorly: Middle cranial fossa
 Posteriorly: mastoid air cells
 Inferiorly: parotid gland
 Anteriorly: Temporomandibular joint
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Diseases
 Conductive hearing loss
 Cerumen impaction
 Foreign Bodies Occlusion
 Growths/Tumors (Exostoses (most common))
 Infections (External Otitis)(“swimmer ear”)
 Furuncle(A Furuncle is a painful infection of a hair
follicle located in the ear canal.)
 Microtia (small ear)
 Atresia(lack of fully developed ear canal)
 Anotia (absent ear)
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furuncle
microtia
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