Dr. Ahmed Fathalla Ibrahim

THE EARTHE EAR

• Is an organ of Is an organ of hearing hearing & & balancebalance

• Consists of three parts:Consists of three parts:

1.1. External Ear External Ear

2.2. Middle EarMiddle Ear

3.3. Internal EarInternal Ear

THE EXTERNAL EARTHE EXTERNAL EAR

• AURICLEAURICLE

• EXTERNAL EXTERNAL AUDITORY AUDITORY MEATUSMEATUS

AURICLE:AURICLE:

• Shape:Shape: consists of a thin plate of elastic cartilage

• Function:Function: collects air vibrations

• Motor supply:Motor supply: facial nerve

EXTERNAL AUDITORY MEATUSEXTERNAL AUDITORY MEATUS

• Shape:Shape: a curved tube formed of elastic cartilage (outer 1/3) & tympanic plate of temporal bone (inner 2/3)

• Function:Function: conducts sound waves from auricle to tympanic membrane

THE MIDDLE EAR THE MIDDLE EAR (TYMPANIC CAVITY)(TYMPANIC CAVITY)

• Definition:Definition: air-containing cavity in petrous part of tympanic bone, lined with mucus membrane

• Function:Function: transmits vibration of tympanic membrane to perilymph of internal ear

• Communications:Communications:1. Anteriorly: with nasopharynx (through

auditory tube)2. Posteriorly: with mastoid antrum3.3. Nerve supply:Nerve supply: tympanic branch of

glossopharyngeal nerve

THE MIDDLE EARTHE MIDDLE EAR

• Roof:Roof: tegmen typani (thin plate from petrous temporal bone), separates middle ear from temporal lobe of brain

• Floor:Floor: thin plate of bone, separates middle ear from superior bulb of internal jugular vein

THE MIDDLE EARTHE MIDDLE EAR• Anterior wall:Anterior wall: 1. Superiorly: has 2

openings (for auditory tube & for canal of tensor tympani)

2. Inferiorly: thin plate of bone separating middle ear from internal carotid artery

THE MIDDLE EARTHE MIDDLE EAR

• Posterior wall:Posterior wall:

1.Superiorly: has an opening (aditus to mastoid antrum)

2.Inferiorly: a conical projection (pyramid) for emergence of stapedius

THE MIDDLE EARTHE MIDDLE EAR• Lateral wall:Lateral wall: tympanic

membrane• Medial wall:Medial wall: 1. Promontory: rounded projection

formed by cochlea2. Fenestra vestibuli: oval oval opening,

above & behind promontory, closed closed by base of stapes

3. Fenestra cochleae: round round opening below promontory, closed closed by secondary tympanic membrane

4. Prominence for facial nerve canal: runs backwardbackward above promontory & fenestra vestibuli then curves downwarddownward behind pyramid

THE TYMPANIC MEMBRANETHE TYMPANIC MEMBRANE• Shape:Shape: a thin fibrous

membrane between external & middle ear, has a small depression (umbo) produced by handle of malleus, divided into pars flaccida & pars tensa

• Nerve supply:Nerve supply:• Outer surface: auricular

branch of vagus• Inner surface: tympanic

branch of glossopharyngeal

AUDITORY OSSICLESAUDITORY OSSICLESMALLEUS:MALLEUS:• Head: articulatesarticulates with

body of incus• Neck• Handle: firmly attached to

medial surface of tympanic membrane, receives insertioninsertion of tensor tympani

• Anterior process• Lateral process: attached

to anterior & posterior malleolar folds of tympanic membrane

AUDITORY OSSICLESAUDITORY OSSICLES

INCUS:INCUS:• Body: articulates articulates

with head of malleus• Long process:

articulatesarticulates with head of stapes

• Short process: attached to tympanic cavity

AUDITORY OSSICLESAUDITORY OSSICLES

STAPES:STAPES:• Head: articulatesarticulates

with long process of incus

• NecK: receives insertioninsertion of stapedius

• Base: attached to fenestra vestibuli

MUSCLES OF OSSICLESMUSCLES OF OSSICLES

TENSOR TYMPANI:TENSOR TYMPANI:• Origin: auditory tube• Insertion: handle of malleus• Nerve supply: mandibular of trigeminal • Action: damps down vibration of tympanic

membraneSTAPEDIUS:STAPEDIUS:• Origin: pyramid• Insertion: neck of stapes• Nerve supply: facial • Action: damps down vibration of stapes

FACIAL NERVEFACIAL NERVE• Course:Course: runs in facial canal

then emerges through stylomastoid foramen

• Branches:Branches:1. Nerve to stapedius2. Chorda tympani: carries taste taste

fibersfibers from anterior 2/3 of tongue & preganglionic preganglionic parasympathetic fibersparasympathetic fibers to submandibular & sublingual salivary glands

3. Greater petrosal nerve: carries taste fiberstaste fibers from soft palate & preganglionic parasympathetic preganglionic parasympathetic fibersfibers to lacrimal, nasal & palatine glands

THE INTERNAL EARTHE INTERNAL EAR

• Lies in petrous part of temporal petrous part of temporal bonebone

• Consists of:

1. Bony labyrinth

2. Membranous labyrinth

BONY LABYRINTHBONY LABYRINTH

• Consists of:

1. Vestibule

2. 3 semicircular canals

3. Cochlea• They are cavities

inside bone, filled with perilymph in which membranous labyrinth is suspended

MEMBRANOUS LABYRINTHMEMBRANOUS LABYRINTH• Lodged within bony

labyrinth• Filled with endolymph &

surrounded by perilymph• Consists of:1. Utricle & saccule: in

vestibule2. 3 semicircular ducts: in

semicircular canals3. Cochlear duct: in

cochlea

VESTIBULOCOCHLEAR NERVEVESTIBULOCOCHLEAR NERVE

• Divides into:

1. Vestibular nerve: supplies utricle, saccule & semicircular ducts

2. Cochlear nerve: supplies cochlear duct