The Ear by:rmz rabadi

7/31/2019 The Ear by:rmz rabadi

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The Statoacoustic Organ

The Ear

Sato : from static \ balanceacoustic : auditory \ hearing Fnx


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The Ear

Divides into 3 parts:

External Ear

Middle Ear

(Tympanic cavity)

ossicles

Inner Ear

(Labyrinth)hearing & balance

* The middle and the innerear are located within thepetrous part of the

temporal bone inside theskull


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External Ear

Auricle & EAM

-Auricle (pinna):

made of elastic cartilage covered by theskin except for the lobule which containa pad of fat covered by skin

fnx :collects sound waves

divided into:

lobule

helix & anti helix

tragus & antitragus

scapha

concha

triangular fossa


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External Acoustic Meatus (EAM)

Out 1/3: cartilageInner 2/3: bone \ pertrous part of

temporal

Fxn.:

Conducts sound waves

Lined with skin:

sebaceous &

ceruminous glands

Cerumen (earwax)

Osteocartilaginous(bone+cartilage) tube extends from auricleto T.M. (~2-3 cm)


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Tympanic Membrane

Thin, oval, semitransparent memb. Of ~ 1 cm in diameter.

- Separates the external ear from middle ear

-Lined by:skin from outside and mucus

membrane from insideConcave outside & convex inside

(because its being tense by the tensortympany m. \ important in giving thevibrations to produce sounds )

Nerve Supply by the trigemenal nerve :auriculotemporal +glossopharyngeal

Divided into:

4 areas


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1. Pars Flaccida: upper third area \ red in colour

superiorly

avoided during surgery because it is rich in blood supply

2. Pars tensa:

remaining

3. Umbo:

central depression(peak of concavity)

4. Cone of light

radiates ant. Inf . From umbo

It is not real , it is a reflection of light and if we see it anterior inferior to the umbo this isan indication of a healthy tympanic membrane


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Innervation of the tympanicmem.

The outer part of the tympanic membraneis made of skin , it is innervated by thesame nerve that supply the external ear

which is the ( auriculotemporal n )

The inner part of the tympanic membraneis made of mucus membrane and it is

innervated by the same nerve that supplythe inner ear which is the (glossopharyngeal n )


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When we examine a patient with theotoscope we replace it as fallows to get abetter view :

- Adult : we have to put the auricle posteriorsuperior

- in infants : we put it just post

* An indication about a healthy tympanicmembrane is to see the cone of lightradiation anterior inferior from the umbo


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Middle EarThe Tympanic Cavity

Air filled chamber within petrous part of temporal bone that is lined withm.m. ( the air reach it from eustacian tube )

Divided into:

1-Tympanic cavity proper : behind the tympanic membrane itself

2-epitympanic recess

small space sup. To the tympanic membrane

-Communicates:

Ant.: with the nasopharynx through the Eustachian tube

Post.: with the mastoid air cells through the audits to mastoid antrum

* So your mark is the roof of the tympanic membrane :everything behind the tympanic membrane is the main part of the tympaniccavity , the remaining space above the tympanic membrane is theepitympanic recess .


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Boundaries of Tympanic Cavity

Ant. Wall (Carotid):

Separates the tympanic cavity from the carotid canalContains (sup.):

auditory tube opening

tensor tympani m.

Post. Wall (Mastoid):Separates the middle ear from the mastoid air cells

Contains:

aditus (L, access) to mastoid antrum

(sup.) communicates the middle ear with the mastoid air cells

Pyramidal eminence

a hollow bony cone enclosing the stapedius m


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Medial wall (labyrinthine):

Separates the middle ear from the inner ear

Contains:

the Promontory

bony convexity formed by the base of the cochlea is resting

there

tympanic plexus

over the promontory

formed by the glossofaringeal (tympanic nerve )

round & oval windows


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- Stapedius m .: fnx in stabilizing the stapes preventing excessive movementof the stapes reducing the oscillatory range .It is the smallest skeletal m. in our body stabilizing the smallest bone

- The medial wall of the inner ear also called the labyrinthine because itopens to the labyrinthine in the inner ear

- Promontory : a large bluge area on the medial wall it is a bony convexityformed by the base of the cochlea that resting there

- The glossopharengeal nerve will give a branch to the middle ear and overthe promontory it starts to divide forming a tympanic plexus formed by thetympanic nerve from the glossopharyngeal responsible for the sensationwithin the middle ear


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Lateral wall (membranous):

Formed by the inner part oftympanic membrane

Separates the middle earfrom the external ear


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Roof (Tegmental wall):

Separates the middle ear from the floor of the middle cranial fossa

Formed by thin plate of bone( petrus part of temporal bone ) called

tegmen tympani

Floor (Jugular wall):

Thin bony plate that

Separates the middleear from the IJV


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Contents of Middle Ear3 bones\ 2 muscles \2 nerves

Auditory ossicles:

malleus, incus, stapes

Muscles:

stapediustensor tympani m.

Nerves:

chorda tympanitympanic plexus


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Auditory Ossicles

Malleus (L, hammer): this bone is handlebetween the tympanic mem. Outside And

the tensor tympani inside

head:

in epitympanic recess

articulates with th incus

Neck

Handle:

attached to the tympanic mem. And thetensor tympani


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Tensor tympani has a tendon because itis attached between soft tissue ( tympanicmembrane ) and hard tissue ( handle of

the malleus )

Action : when it contract it tense thehandle of the malleus inside so it tense the

tympanic membrane


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Incus (L, anvil):

Body

epitympanic recess

articulates the headof the malleus

Long limb

articulates with thestapes m

Short limb

Attached to the posterior

Wall to fix it in its place


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Stapes\ oval in shape (L, stirrup)

Base (foot plate)

attached to oval window

Ant. & Post. limbs

Neck

attached to Stapedius m

Head

articulates with incus


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Stapedius Muscle

Origin : pyramidal eminence on the mastoid wall ( posterior wall ofthe tympanic cavity )

Insertion : Stapes neck

Innervation :nerve to stapedius from facial nerve

Action : stabilize the stapes

The smallest skeletal muscle in the human body,

Stabilizes the smallest bone in the body


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Tensor Tympani Muscle

Origin : from the canal in the anterior wall of the tympaniccavity

Insertion : handle of the malleus

Innervation : nerve to medial petergoid from mandibular nerve

Action : tense the tympanic membrane


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Otitis Media

Infection of middle ear

Signs & Symptoms (what is the difference?):

earache, impaired hearing

bulging red T.M. due to pus in mid. Ear

Complications:

blockage of pharyngotympanic tube

perforation of T.M.

Mastoiditis? Can go posteriorly to mastoid air cells

Osteomyelitis (bone infection)of tegmen tympani

spread sup. To middle cranial fossa \ lead to meningitis


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The Inner Ear

Consists of:

Bony labyrinth:

cavities within bone

Membranous labyrinth:

memb. Sacs & ducts

within these cavities


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Bony Labyrinth

3 parts

Vestibule:small oval chamber

balance

Semicircular canals:

sup. (ant.)

post. (inf.)

Lat.

3 different planes

Communicate with semicircular ducts

Cochlea:

shell-shaped, Fxn. In hearing


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Membranous Labyrinth

Utricle & Saccule:

sacs within vestibule

Semicircular ducts:

within semicircular canals

Cochlear duct:

within cochlea


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Done by

RMZ RABADI

wish you all the luck

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The Ear by:rmz rabadi