The document summarizes the anatomy and physiology of the ear. It is divided into three main parts: the external ear, middle ear, and inner ear. The external ear collects sound waves and directs them through the external auditory canal to the tympanic membrane. The middle ear contains three small bones (ossicles) that transmit sound vibrations from the tympanic membrane to the inner ear. The inner ear, or labyrinth, contains the cochlea for hearing and semicircular canals for balance. It converts sound vibrations into neural signals that are sent to the brain.

1. ANATOMY AND PHYSIOLOGY OF EAR
PRESENTED BY BATCH-J STUDENTS

2. Ear
 Mainly divided into 3 parts
 1)External ear 2)
 Middle ear
 3)Inner Ear

3. External Ear
 Further divided into
 Pinna or Auricle
 External acoustic meatus
 Tympanic membrane
 1)Parts of pinna or arucle
Are shown
Except lobule and incisura terminalis
The whole pinna is made of up
Elestic cartilage cover with bone

4. External acustic meatus or canal.
 It is about 24cm long. It’s outer 1/3 is cartilaginous while the inner 2/3 is bony.
 It is not straight. Its Outer part is directed upward, backward and medially, While the
inner part is directed downward, forward and medially.
Cartilaginous part
 Small hair and gland(secrets waxs) is mainly restricted to the outer 1/3(8cm) so furuncle
mainly develop here.
 Slightly constricted are between the outer 1/3 and inner 2/3 is called isthmus where
forigen body mainly lodge.

5. Bony part
 Its Form the inner 2/3 of external canal. Skin is not covered by hair and ceruminous
gland.
 Anterioinferior part of the deep meatus beyond the isthmus present a recess called as
anterior recess where discharge and debris of external and middle ear accumulate.

6. Tympanic membrane
 It is a partition between external acustic canal and middle ear.
 It is set obliquely and has posterosuperior part lateral then the anterioinferior part.
 It is about 9-10mm tall 8-9mm wide and 0.1mm thick.
 It is divided into two parts
1)Pars tensa
1)Pars flaccida(Sharpnell’s membrane)

8. 1)Pars Tensa
 It form most of the tympanic membrane.
 It’s pherephry is thicken to form a fibrocartilaginous ring called as anulus tympanicus.
 It’s tent inword at the level of tip of malleus called as Umbo.
 At the anterioinferior quadrant a bright Cone of light can be seen radiating from the tip
of malleus.
2)Pars Flaccida
 It is satuited above the lateral process of malleus between the anterior and posterior
malleal fold
 It is not taut and slightly reddish

9. Layer of tympanic membrane
 Tympanic membrane consist of 3 layers
 1) Outer epithelial layer, continues with skin of meatus.
 2) Inner mucosal layer Which is cantinous with mucosa of the middle ear.
 3) Middle fibrous layer, enclosed the hand of malleus.
 Fibrous layer is thin in Pars Flaccida and is not well organized.

11. Relations of External acustic canal
 Superiorly: Middle cranial fossa
 Inferiorly: Parotid glandl
 Anteriorly: Temporomandibular joint
 Posteriorly: Mastoid air cell and facial nerve

12. Nerve supply
 Pinna
 1. Great Auricluler nerve (C2,3) supply most of the medial side and only
the posterior part of lateral side.
 2. Lesser occipital (C2) supplies upper part of medial surface.
 3. Auriculotemporal (V3) supplies tragus, crus of helix and the adjacent
part of the helix.
 4. Auricular branch of vagus (CN X), also called Arnold’s nerve, supplies the
concha and corresponding eminence on the medial surface.
5. Facial nerve, which is distributed with fibres of auricular branch of vagus,
supplies the concha and retroauaricular groove.

13.  External auditory cana
 Auriculotemporal (V3) supply roof and anterior wall.
 Ariculer branch of vagus supply floor and posterior wall.
 Posterior wall also receive sensery fiber of CN-7 through ariculer branch of vagus.
 Tympanic membrane
 Auriculotemporal (V3) supply anterior half
 While Ariculer branch of vagus supply posterior half
 Medial side is supply by tympanic branch of CN-9.

15. MIDDLE EAR
 The middle ear together with eustachian tube, aditus, antrum and Mastoid ear cell is
called middle ear cleft.

16. Middle ear
The middle ear extends much beyond the limits of tympanic membrane, and is sometimes
divided into:
1)Mesotympanum (lying opposite the pars tensa).
2) Epitympanium Or the Attic (lying above the pars tensa but medial to Shrapnell’s
membrane and the bony lateral attic wall)
3) Hypotympanum (lying below the level of pars tensa)
4)Protympanium The portion of middle ear around the tympanic orifice of the eustachian
tube are sometimes called as Protympanium.

18.  Middle ear is like a six sided box with roof, floor, medial, lateral, anterior and posterior walls
 1) Roof: is form by a thin plate of bone called tegmen tympani. This bone separate middle
ear from middle cranial fossa.
 2) Floor: It is also form by a thin plate of bone, It separate the tympanic cavity from jugular
bulb.
 3) Anterior wall: It is also made by a thin plate of bone which separate the cavity from
Internal carotid artery. It also has two opening; the lower one for eustachian tube and the
upper one for the canal of tensor tympani muscle
 4) Posterior wall: It lies close to the mostoid air cell. A bony projection pyramid is present
to which the tenden of Stapedius muscle attached. Aditus an opening through which attic
communicate with antrum is also present in the posterior wall. Facial recess is a depression in
the posterior wall lateral to the pyramid.

19. Medial wall: it is formed by the lybrinath. Basal coil of the cochlea formed buldge which is
called promontory.
Foot plate of stapis fixed to Oval window. While the Round window is covered by
secondary tympanic membrane.
Above the Oval window there is a canal for facial nerve. If the bone is congenitally defefient
then the facial nerve is vulnerable to infection of middle ear.
Above the canal for facial nerve there is a prominence of lateral semicircular canal.
Processus cochleariformis is a hook like projection in the medial wall anterior to the oval
window. The tensor tympani muscle tenden take trun here and It also marks the level of first
genu of facial nerve

20. Lateral wall: It is largely formed by tympanic membrane and to a lesser extent by a bony
outer attic wall called Scutum

22. Mastoid antrum
 It is a large air containg space in the upper part of Mastoid and
communicate with the attic through aditus
 Its roof is formed by tegmen antro which is a continuation of tegmen
tympani and separate from middle cranial fossa.

23. Mastoid and its air system
Mastoid consists of bony cortex with a “honeycomb” of air cells underneath.
Depending on development of air cell, three types of mastoid have been described.
1. Well-pneumatized or cellular. Mastoid cells are well-developed and intervening septa
are thin.
2. Sclerotic or Acellular: There is no cell or marrow space.
3. Diploetic. Mastoid consists of marrow spaces and a few air cells.
With any type of mastoid pneumatization, antrum is always present.
In sclerotic mastoids, antrum is usually small.
Depending on the location, mastoid air cells are divided into:
1. Zygomatic cells (in the root of zygoma).
2. Tegmen cells (extending into the tegmen tympani).
3. Perisinus cells (overlying the sinus plate).
4. Retrofacial cells (round the facial nerve).

24. 5. Perilabyrinthine cells (located above, below and behind the labyrinth, some of them
pass through the arch of superior semicircular canal. These cells may communicate with the
petrous apex).
6. Peritubal (around the eustachian tube. Along with hypotympanic cells they also
communicate with the petrous apex).
7. Tip cells (which are quite large and lie medial and lateral to the digastric ridge in the tip
of mastoid).
8. Marginal cells (lying behind the sinus plate and may extend into the occipital bone).
9. Squamosal cells (lying in the squamous part of tempo-ral bones).
Abscesses may form in relation to these air cells and may sometimes be located far from
the mastoid region.

26. Ossicles of middle ear
 There are three ossicles in the middle ear, the malleus, incus and stapes.
 The malleus has head, neck, handle (manubrium), a lateral and an anterior
process.
 Head and neck of malleus lie in the attic. Manubrium is embedded in the
fibrous layer of the tympanic membrane.
 The lateral process forms a knob-like projection on the outer surface of the
tympanic membrane and gives attachment to the anterior and posterior
malleal (malleolar) folds

27.  The incus has a body and a short process, both of which lie in the attic, and a long process
which hangs vertically and attaches to the head of stapes
 The stapes has a head, neck, anterior and posterior crura, and a footplate. The footplate is
held in the oval window by annular ligament.
 The ossicles conduct sound energy from the tympanic membrane to the oval window and
then to the inner ear fluid.

29. Intratympanic muscles
 There are two muscles, tensor tympani and the stapedius,
 Tensor tympani attaches to the neck of malleus and tenses the tympanic
membrane
 Stapedius attaches to the neck of stapes and helps to dampen very loud
sounds thus preventing noise trauma to the inner ear.
 Stapedius is supplied by a branch of CN VII while tensor tympani is
supplied by a branch of mandibular nerve (V3)

30. Lining of middle ear cleft
 Mucous membrane of the nasopharynx is continuous with that of the middle ear, aditus,
antrum and the mastoid air cells. It wraps the middle ear structures: the ossicles,
muscles, ligaments and nerves.
 Middle ear cantain nothing but air. And All the structure lie outside mucous membrane.
 Histologically eustachian tube is lines by Cilliated Epithelium, pseudostratified columnar
in cartilaginous part and simple columnar in bony part
 Tympanic membrane epithelium-anterior part: Cilliated columnar and posterior part
Cuboidal.
 Epitympanium and Mastoid air cell is lined by noncilliated epithelium.

31. Inner ear
 The internal ear or the labyrinth is an important organ of hearing and
balance.
 It consists of a bony and a membranous labyrinth.
 The membranous labyrinth is filled with a clear fluid called endolymph
 while the space between membranous and bony labyrinths is filled with
perilymph.

32. Bony labyrinth
 It consists of three parts: the vestibule, the semicircular canals and the cochlea

33.  Vestibule:
 It is the central chamber of the labyrinth.
 In its lateral wall lies the oval window.
 The inside of its medial wall presents two recesses, a spherical recess, which lodges the
saccule, and an elliptical recess, which lodges the utricle.
 Below the elliptical recess is the opening of aqueduct of vestibule through which passes
the endolymphatic duct.
 In the posterosuperior part of vestibule are the five openings of semicircular canals

34.  Semicircular canals:
 They are three in number, the lateral, posterior and superior, and lie in planes at right
angles to one another.
 Each canal has an ampullated end which opens independently into the vestibule and a
nonampullated end.
 The nonampullated ends of posterior and superior canals unite to form a common
channel called crus commune.
 Thus, the three canals open into the vestibule by five openings.

35. 

36.  Cochlea:
 The bony cochlea is a coiled tube making 2.5 to 2.75 turns round a central pyramid of
bone called modiolus.
 The base of modiolus is directed towards internal acoustic meatus and transmits vessels
and nerves to the cochlea.
 Osseous spiral lamina is thin plate of bone which divides the cochlea incompletely and
give attachment to basilar membrane.
 Promontory is due to basal coil of cochlea
 Bony cochlea has 3 compartments
1)Scala vestibuli
2)Scala tympani
3) Scala media or the membranous cochlea.

37.  The scala vestibuli and scala tympani are filled with perilymph and communicate with
each other at the apex of cochlea through an opening called helicotrema.
 Scala vestibuli is closed by the footplate of stapes which separates it from the air-filled
middle ear. The scala tympani is closed by secondary tympanic membrane
 It is also connected with the subarachnoid space through the aqueduct of cochlea

40. Membraneous labyrinth
 It consists of the cochlear duct, the utricle and saccule, the three semicircular ducts, and
the endolymphatic duct and sac.
 1) Cochlear Duct:
 It is Also called membranous cochlea or the scala media
 It is a blind coiled tube.
 It appears triangular on cross-section and its three walls are formed by:
 A)The basilar membrane, which supports the organ of Cort.
 B)The Reissner’s membrane, which separates it from the scala vestibule.
 C)The stria vascularis, which contains vascular epithelium and is concerned with secretion of
endolymph.
 Cochlear duct is connected to the saccule by ductu reuniens. The length of basilar membrane
increases as we proceed from the basal coil to the apical coil.
 It is for this reason that higher frequencies of sound are heard at the basal coil while lower
ones are heard at the apical coil

41.  2)Utricle and Saccule. The utricle lies in the posterior part of bony vestibule.
 It receives the five openings of the three semicircular ducts. It is also connected to the
saccule through utriculosaccular duct.
 The sensory epithelium of the utricle is called macula and is concerned with linear
acceleration and deceleration.
 The saccule also lies in the bony vestibule, anterior to the utricle and opposite the stapes
footplate.
 Its sensory epithelium is also called macula. Its exact function is not known. It probably
also responds to linear acceleration and deceleration

42.  3)Semicircular Ducts:
 They are three in number correspond exactly to the three bony canals.
 They open in the utricle.
 The ampullated end of each duct contains a thickened ridge of neuroepithelium called
crista ampullaris.

43. 4)Endolymphatic Duct and Sac:
Endolymphatic duct is formed by the union of two ducts, one each from the saccule and the
utricle.
It passes through the vestibular aqueduct.
Its terminal part is dilated to form endolymphatic sac, which lies between the two layers of
dura on the posterior surface of the petrous bone.
Endolymphatic sac is surgically important. It is ex-
posed for drainage or shunt operation in Ménière’s disease.

44. Inner ear fluid and their circulation
 There are two main fluids in the inner ear: perilymph and endolymph.
 1) Perilymph:
 It resembles extracellular fluid and is rich in Na ions. It fills the space between the bony
and the membranous labyrinth.
 It communicates with CSF through the aqueduct of cochlea which opens into the scala
tympani near the round window. In fact this duct is not a direct communication but
contains connective tissue resembling arachnoid through which perilymph percolates.
 There are two views regarding the formation of perilymph:
 1) It is a filtrate of blood serum and is formed by capillaries of the spiral ligament.
 2) it is a direct continuation of CSF and reaches the labyrinth via aque-duct of cochlea

45.  2) Endolymph:
 It fills the entire membranous labyrinth and resembles intracellular fluid, being rich in K
ions.
 It is secreted by the secretory cells of the stria vascularis of the cochlea and by the dark
cells (present in the utricle and also near the ampullated ends of semicircular ducts).
 There are two views regarding its flow:
 (i) longitudinal, i.e. endolymph from the cochlea reaches saccule, utricle and
endolymphatic duct and gets absorbed through endolymphatic sac, which lies in the
subdural space.
 (ii) radial, i.e. endolymph is secreted by stria vascularis and also gets absorbed by the
stria vascularis.

46. Labyrinth blood supply
 The entire labyrinth receives its arterial supply through labyrinthine artery,
which is a branch of anterior-inferior cerebellar artery but sometimes from the
basilar.
 In the internal auditory canal it divides in the manner shown in Venous
drainage is through three veins, namely internal auditory vein, vein of cochlear
aqueduct and vein of vestibular aqueduct, which ultimately drain into inferior
petrosal sinus and lateral venous sinus
 It is to be noted that:
 1) Blood supply to the inner ear is independent of blood supply to middle ear
and bony otic capsule, and there is no cross circulation between the two.
 2) Blood supply to cochlea and vestibular labyrinth is segmental, therefore,
independent ischaemic damage can occur to these organs causing either
cochlear or vestibular symptoms.

47. 

48. 

49. PHYSIOLOGY
OF EAR

50. AUDITORY SYSTEM
ORGAN OF CORTI ; THERE ARE THE FOLLOWING 4 PARTS OF THE ORFGAN OF CORTI
1. TUNNEL OF CORTI ;
TUNNEL OF CORTI CONTAINS CORTILYMPH
2. HAIR CELLS ;
THEY ARE IMPORTANT RECEPTOR CELLS OF HEARING AND TRANSDUCE SOUND ENERGY
INTO ELECTRICAL ENERGY .
A;INNER HAIR CELLS
FORM A SINGLE ROW IT IS HIGHLY SUPPLIED WITH AFFERENT COCHLEAR FIBERS AND GIVES
SIGNELS TO BRAIN
B; OUTER HAIR CELL
OUTER HAIR CELLS RECEIVE EFFERENT FIBERS FROM OLIVERY COMPLEX AND IS CONCEREND
WITH MODULATING THE FUNCTION OF INNE RHAIR CELLS

51.  3 SUPPORTING CELL;
THERE ARE TWO TYPES OF SUPORTING CELLS DIETER,S CELL AND HENSEN CELLS
 4 TECTORIAL MEMBRANE ;
 IT OVERLIES THE ORGAN OF CORTI .
 THE SHEARING FORCE BETWEEN THE HAIR CELLS AND TECTORIAL MEMBRANE PRODUCES
THE STIMULUS TO HAIR CELLS
 NERVE SUPPLY OF HAIR CELLS ;;
 95 %OF AFFERERNT FIBERS OF SPIRAL GANGLION SUPPLY INNNER HAIR CELLS WHILE
5%SUPPLY THE OUTER HAIR CELLS
 EFFERENT FIBRS TO HAIR CELLS COM FROM OLIVOCCHLEAR BUNDLES .THE CELL BODIES OF
THESE FIBERS ARE LOCATE IN THE SUPERIOR OLIVERY COMPLEX
 EACH COCHLEA SENDS FIBERS TO BOTH SIDES OF BRAIN

53.  AUDITORY NEURAL PATHWAYS AND THEIR NUCLIE ;;
 HAIR CELLS ARE INNERVATED BY DENDRITES OF BIPOLAR CELLS OF SPIRAL GANGLION
WHICH IS INNERVATED BY ROSENTHAL,S CANAL
 AXONS OF THESE BIPOLAR CELLS FORM THE COCHLEAR DIVISION OF CN VIII AND END IN
COCHLEAR NUCLIE THE DORSAL AND VENTRAL ON EACH SIDE OF MADULLA
 THE ASCENDING PATHWAY SEQUENTIALLY FROM BELOW TO UPWORD
 SUPERIOR OLIVERY NUCLEUS
 NUCLEUS OF LATERAL LIMNISCUS
 INFERIOR COLLICULUS
 MEDIAL GENECULATE BPDY
 AUDITORY CORTEX
 THE AUDITORY FIBERS TRAVEL VIA IPSILATERAL AND CONTRALATERAL ROUTES AND HAVE
MANY DECUSSATION POINTS
 BROADMAN AREA ;; IT IS THE CEREBRAL PORTION CONCERNED WITH HEARING

54.  MECHANISM OF HEARING
 SOUND IS SIGNAL IS COLLECTED BY THE PINNA OF EAR PASSES THROUGH THE XTERNAL
CANAL IT REACHES THE TEMPANIC MEMBRANE AND STRIKES IT
 TEMPANIC MEMEBRANE GIVES THESE VIBRATIONS TO MELLIUS AND THEN TO INCUS AND
LASTLY GIVEN TO STAPES
 STAPES GIVES THESE SIGNALS TO LABIRYNTHINE OF INNER EAR HICH CONVERTS THESE
SIGNALS TO ELECTRICAL SIGNALS WHICH ARE THEN TRANSMITTED THROUGH VIII NERVE
TO BRAIN
 PAYHWAYS OF TRANSMISION
 MECHNICAL CONDUCTION ( CONDUCTIVE APPARATUS )
 ELECTRICAL CONDUCTION ( SENSORY SYSTEM OF COCHLEA )
 CONDUCTION OF ELECTRICAL SIGNALS TO BRAIN ( NEURAL PATHWAY )

56.  IMPEDENCE ;; IMPEDENCE IS THE RESISTANCE SHOWN TO SOUND WAVES WHEN IT ENTERS
FROM ONE MEDIUM TO ANOTHER MEDIUM
 MECHANISM OF IMPEDENCE ;;
• LEVER ACTION OF OSSICLES ; HANDLE OF MALLEUS IS 1.3 TIMES LONG THAT IS WHY IT
PROVIDES MECHANICAL ADVANTAGE OVER STAPES
• HYDRUALIC ACTION OF TYMPANIC MEMBRANE ;; AREA OF TYMPANIC MEMBRANE IS
LARGER THAN THE AREA OF STAPES FOOTPLATE
• CURVED MEMBRANE EFFECT OF TYMPANIC ; MOVEMENT OF TYPANIC IS MORE AT THE
PERIPHERY THEN AT THE CENTER

57.  VESTIBULAR SYSTEM
 THIS SYSTEM IS MAINLY CONCERNED WITJH BALANCE AND POSITION OF BODY
 IT HAS THE FOLLOWING PARTS .
 PERIPHRAL RECEPTORS ; THERE ARE TWO TYPES OF RECEPTORS
• CRISTEA ; THEY ARE LOCATED IN THE SEMICIRCULAR CANAL
• THEY RESPOND TO ANGULAR MOTIONS
• MACULA ;; THEY ARE PRESENT IN THE OTOLITH ( UTRICLES AND SACCULES )
• MACULA OF UTRICLE LIES THE FLOOR IN HORIZONTAL PLANE
• MACULA OF SACCULE LIES IN MEDIAL WALL IN VERTICAL PLANE
THEY SENSE POSITION OF HEAD IN RESPONSE TO GRAVITY AND LINEAR ACCELERATION

59.  VESTIBULAR NERVE ;;
 THE VESTIBULAR GANGLION IS LOCATED IN THE LATERAL PART OF INTERNAL ACOUSTIC
MEATUS
 IT CONTAINS BIPOLAR CELLS
 THE DISTAL PROCESSES OF BIPOLAR CELLS INNERVATE THE SENSORY EPITHELIUM OF
LABYRINTH
 THE CENTRAL PROCESSES AGREGATE TO FORM VESTIBULAR NERVE
 VESTIBULAR NUCLIE ;;;
 THEY ARE LOCATED IN THE MADULLA AND PONS OF HIND BRAIN
 THEY ARE FOUR IN NUMBER
• SUPERIOR
• INFERIOR
• MEDIAL
• LATERAL