h&n anatomy- the ear

8/2/2019 H&N anatomy- the ear

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When we speak about the ear we refer to it as statoacoustic organ,

what are we mean?

because it has manly 2 functions:Stato from static (balance); when

we stand up (equilibrium). and it has an acoustic function: auditory

(hearing).

-The ear is divided into 3 mean parts:

The Statoacoustic Organ

The Ear


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External Ear, Middle Ear and Inner Ear.

-The Middle Ear and Inner Ear located within the petrous part of

temporal bone inside the skull.

-The external ear; is made of the Auricle outside which we see it and

the canal that conduct the sound waves from the external ear from the

auricleall the way to tympanic membrane this canal we refer to it as

external auditory meatus.

-The middle ear; the chamber that containing the ear ossicles (

) which are:malleus, incus, stapes.this area we refer to it astympanic cavity.

-The Tympanic Cavity; its a little bit confusing because of the openings

and orientation in it, sothats why we refer to it as tympanic from maze

(tympanic is a Greek word that means maze).

So;external ear which is auricle and external auditory meatus until

tympanic membrane, the tympanic membrane is the part that separate

the external ear from the middle ear, the middle ear is a small chamber

that containing the ear ossicles, after that there is the inner ear or the

labyrinth (the part that containing hearing and the balance organs-

Cochlea and the Vestibule-).

-The cochlea; that part to hearing, the vestibule is the part related to

equilibrium.

-When we speak about the external ear: the first part of it is the

auricle; when we look to a real auricle in any view we will see that each

auricle is made by the way ofelastic cartilage covered by skin except in


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the lower part which we referred to it as a lobule, the elastic cartilage is

replaced by a pad of fat.

-So most of the auricle is elastic cartilage it collects the sound waves-

function of it-, its made of several structures, elevations and

depressions and they called just named them:

the helix: which is the most big elevations at the periphery-outer

side- of the auricle.

anti helix: is the elevations opposite to the helix.

the scapha(the scaphoid fossa): the groove between the helix andanti helix.

tragus(lingual): it is a structure in scapha from anterior like the

tongue and the other elevation opposite to it called as antitragus.

the concha(the concha fossa): the deepest depression in the auricle

that leads to external auditory meatus.

External auditory meatus: when we want to define the meatus -by

meatus we mean a canal- the meatus is an Osteocartilaginous tube

(osteo means bone cartilaginous means cartilage) this indicate that

the outer third of it is made by cartilage, those cartilages are


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contributing to the auricle and also contributing to the lateral third of

the meatus so the outer third is cartilage but the inner 2/3 is bone,,,

which bone? Temporal bone; because this within the petrous part of

temporal bone.

-so the inner 2/3 is bone and it extends from the auricle outside all the

way to the tympanic membrane (2-3 cm in length),within it its covered

by skin and the skin until the tympanic membrane where it reflected to

go back again, so even the outer side of the tympanic membrane is also

covered with the skin but the skin in the meatus here it has specific

glands -special kinds of glands- in additionto the sebaceousglandwerefer to them as ceruminous gland, ceruminous gland is the gland

that secret the serumen-the earwax.

-tympanic membrane: when we look to any tympanic membrane with

an otoscope (its a laminating light within the ear to see the tympanic

membrane), we will see that is a thin, oval shape,semitransparent

membrane and of ~ 1 cm in diameter.

The tympanic membrane is separating the external ear from middle ear

and it slid from outsideskin but from inside within the middle fossa,

the middle ear with Mucous membrane.

So it has a concave outside and its convex inside towards the middle

ear, because it being tense through a muscle that called tensor

tempany muscle because it tenses the tympanic membrane, this

tensing is very important to keep the membrane tense for the

vibration; when the sound waves start to hit the membrane, the

membrane starts to vibrate producing change in the sound waves into


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vibrations and this vibrations in theinner ear will later be change into

nerve signals.

-the nerve supply to tympanic membrane: it depends in what the

nerve supply of the outer and the middle ear which is trigeminal nerve.

-From outside the sensation to the skin that covering the tympanic

membrane is the auriculotemporal nerve but from inside to the

mucous membrane covering the tympanic membrane is

glossopharyngeal nerve; which is the nerve that it responsible for

sensations in the middle ear(cranial nerve #9).

When we look to the membrane from otoscope we will see it compose

from 4 main regions :

The first one: The most superficial area, is the upper third areawhich we refer to it as Pars Flaccida,

Flaccid mean it gives a red

color ,,,why?

Because its rich in blood supply, most of artery that supply the

tympanic membrane located in the superior third of it, so the

superior part of the tympanic membrane we refer to it as pars


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Flaccida, we can also say flaccid part and we have to avoid this part

during any surgery through the tympanic membrane to avoid

hemorrhage.

and all remaining parts is the tense part of the tympanic membrane

and we see how it tense because we can see the direction of the

fibers radiating there, once we see the direction of all these fibers

this all part is refer to as the tense part called the pars tensa of

tympanic membrane

In the middle of the tympanic membrane (the peak of concavity) we

refer to it as umbo, the umbo of the tympanic membrane so parstensa, pars flaccida, umbo

-Now from the umbo why we speak about the umbo because

when we look to otoscope we will see that there is a radiation or a

reflection of light going from the umbo anterior to the inferior

always this reflection of light we refer to it as cone of light .

The cone of light is not real actually its a reflection of light; whenwe insert the otoscope, and this is very important sign for a healthy

tympanic membrane so when we look to the tympanic membrane

through the meatus using the otoscope if you see the cone of light

that indicates everything is normal (the tensity of the membrane is

okay)

-However; if there is any problem in the light resulting ininflammation infection and whatever the cone of light will change in

its angulations or in its presents.

So anindication about healthy tympanic membrane is to see

the cone of light radiating interior inferior from the umbo.


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When we put the otoscope we have to put the auricle posteriorsuperior in the adult but in infant just posterior, so that to get the

meatus straight into the tympanic membrane after u get the auricle

there u get the otoscope and u can see the pars flaccida, the pars

tensa, the umbo and the cone of light.

That all thing about the tympanic membrane.

The middle ear


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Is an ear field space within the petrous part of temporal bone, the air

reach to it from the Eustachian tube, that is find usually through the

mucous membrane varies type of epithelial in the mucous start from

anterior respiratory with auditory then become simple cuboidal tomastoid simple squamous.

It divided into two main parts:The tympanic cavity proper: the part that behind the tympanic

membrane itself we refer to it as main part, proper is this part.

epitympanic recess:, the top( the fundus, the dome shape) ofmiddle ear, epi means above and recess above tympanic cavity these

is also show the clinicians usually refer to it as the attic, a small space

usually superior to the tympanic membrane.

.

the middle ear -when we look to it in a sagittal section within the

middle ear- it communicate anteriorly with the nasopharynx

through Eustachian tube (pharyngio tympanic tube between the

so your mark is the roof of the

tympanic membrane all thing behind

the tympanic membrane is the main

part of tympanic cavity the remaining

space above the tympanic membrane

is the epitympanic recess


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pharynx and tympanic cavity) but posteriorly it communicates with

mastoid air cells through the aditus to mastoid antrum.

- the entrance to this large cavity within the mastoid which we call it

the antrum since all the mastoid air cells communicate there we call

it the mastoid antrum and the entrance from the middle ear into this

antrum is the access of mastoid antrum which also they call it

aditus (access)aditus to mastoid antrum.

so anteriorly Eustachian tube to the nasopharynx posteriorly additus

to mastoid antrum which communicated to mastoid air cells.

the boundaries of the tympanic cavity:anteriorly: the anterior wall we refer to it as carotid wall, (remember

the meddle located in the petrous part of temporal bone, anterior to

it there is carotid canal which pass through it the internal carotid

artery), so the anterior wall of the tympanic cavity we refer to it as

carotid wall because it separate the tympanic cavity from the

carotid canal so this is called the carotid wall however the wall is

superiorly open with 2 opening:

the first one is the Eustachian tube the other opening is the canal

where the tensor tympani muscle is situated or originated from, so

when we look to the tensor tympani it originate(ascend) from

superior wall then their tendon tern 90 degrees and go laterally to

insert in tympanic membrane

so: in the lateral wall we have the tympanic membrane, in the

medial wall we have the inner ear, and the anterior wall have is the

carotid wall where it contains the auditory tube opening and a canal


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for tensor tympani muscle, the posterior wall which is separating the

middle ear from the mastoid air cells -for that they call it mastoid

wall- .

the mastoid wall it separates the middle ear from the mastoid air

cells, it contains another opening we call it aditus to mastoid

antrum.

so remember this: there is an opening communication betweenthe middle ear and the mastoid air cells thats why when we have

any infections in the middle ear it will affect the mastoid air cells

always, or any infections in the mastoid will goes to the middle earso thats why signs and symptoms of otitis media and mastoiditis

always the same.

Pyramidal eminence: also if we look to the posterior wall u will see

there is pyramidal shape of bone this is the cone of bone, its arising

from the posterior wall of the tympanic cavity, its a hollow(empty

from inside) bony cone( ) why its empty?Because inside it there is muscle called the stapedius muscle, its

stapedius because its go and inserted in the stapes, so its function is

to stabilize the stapes prevent excessive movement of the stapes

reducing the oscillatory range so they call it the stapedius muscle

So when we look to the muscle here, u cannot see it because its

inside this cone of bone but from the tip of the cone u can see thetendon of the muscle arising there all the way to be attach to the

neck of the stapes.


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So u see that at the tip of the pyramidpyramidal eminence- since it

will be open then there tendon ascend and go all the way to attach

to the neck of the stapes.

-Stapedius muscle is the smallest skeletal muscle in your body that

stabilizes the smallest bone in your bodystapes- .

So the pyramidal eminence inclosing the stapedius muscle.

when we look to the tympanic cavity we will see; From posterior

wall the pyramidal eminence this is the bony cone, from its tip we

can see the tendon of the stapedius going out from the tip of the

cone all the way into the stapes.

The medial wall which also called (labyrinthine) wall>>> why?

Because it opens in the labyrinth in the inner ear communicating or

separating the middle ear from the inner ear, on the medial wall you

can see a very large bulge area there, this bulge on the medial wall

which we refer to it as promontory.

Promontory is formed because of the base of the cochlea (the

hearing organ) in the inner ear is resting there so once it resting

there it form convex area towards the middle ear and this area we

refer to it as promontory, so the promontory is bony convexity

because of the base of the cochlea is resting there.

The glossopharyngeal nerve will gives a nerve towards the middle

ear for sensory innervations, the nerve to the middle ear from

glossopharyngeal we call it usually as tympanic nerve.

The tympanic nerve will get inside the middle ear and over the

promontory it start to divide forming a plexus this plexus usually see


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it over the promontory we call it tympanic plexus formed by the

tympanic nerve from glossopharyngeal and its responsible for

sensation within middle ear.

The tympanic nerve itself is 2 part :_1) sensory part ( somatic )_2)autonomic part ( parasympathetic )>>>>>> has nothingrelated with middle ear , thy still with each other then leave from

plexus by anterior surface of the middle ear through middlecranial fossa . So, they called lesser petrosal nervewhich gothrough foramen ovali down into the otic ganglion whichresponsible for secretion of slsiva from parotid gland .Also , in the medial wall posteriorly superiorly to the promontorywe can see small opening it is oval window because the stapesresting over it but posteriorly inferiorly there are other window itsaround window .

the window open the middle ear into inner ear . and as the doctortolled you there is vibration need for move the fluid into inner ear toproduce the nerve signals.The stapes start to push in ( inside ) from oval window then it start to topush out ( outside ) by round window.


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lateral wall ( membranous ) :formed by tympanic membrane and separate tympanic cavity from externalear .

The roof ( tegmental wall ) :its avery thin layer of bone ( petrus part of temporal bone ) called tegmentympani which separate middle ear from the floor of middle cranial fossa .

The floor ( jugular wall ) :which separate middle ear from IJV it goes more anteriorlythen descends

down ..

contents of middle ear

Auditory ossicles :malleus , incus , stapes

muscles : stapedius , tensor tympani muscle

Nerve: choroda tympani ( small cord ) >>>>>>> small nerve passingthrough tympanic cavity .

Tympanic plexus.

Note: middle ear >>> 3 bone , 2 muscle , 2 nerve

Malleus:its the hammar and its handle between tympanic membrane outside ( soft

tissue ) and tensor tympani inside


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Note : this muscle has tendon because its attach

between soft tissue ( tympanic membrane ) and

hard tissue (handle of malleus)

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

tympanic membrane .

Incus : (L, anvil )Body:epitympanic recess articulates with the head of the malleus .long limb: articulate with stapes .

Short limb: attached to the posterior wall to fix it in its place .

Stapes: ( l, stirrup )

Its oval shape .

base ( foot plate ) attached to oval window

it has anterior , posterior limbs , neck ( attached to stapes muscle) and

head ( articulates with the incus .

stspedius muscle :origin: pyramidal eminence .

Insertion: stapes neck .Innervation: nerve to stapedius from facial nerve .

Action: stabilize the stapes

tensor tympani muscle:


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Origin: from canal in the anterior wall of tympanic cavity .

Insertion: handle of the malleus .

Innervation: nerve to medial pteregoid from mandibular nerve

Action: tense the tympanic membrane.

Otitis media:infection of middle ear , it can go posteriorly to mastoid air cell .

Symptom( what is the patient complaining about ): *Earache , and impaired hearing

*Signs(what is the doctor or physician discover during physical

examination :Bulging red tympanic membrane due to pus in middle ear .

COMPLICATION:

blockage of pharyngotympanic tube .

perforation .

Mastoiditis : inflammation of air mastoid cell .

osteomyelitis ( bone infection ) of tegmen tympani ( weakest part )>>>spread superiorly to middle cranial fossa can lead to meningitis

The end;

Done by: Asmaa almawas

Habah ramadneh

h&n anatomy- the ear

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