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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