Anatomy of the Ear Flashcards
Parts of the temporal bone
Squamosa
Mastoid
Petrous
Tympanic
Muscles attached to mastoid process
SCM Splenius capitus Longus capitus Digastric Ant, sup, and post auricular
What type of cartilage is the ear made of?
Auricle - elastic
Cartilaginous canal - fibrocartilage
EAC composition
1/3: cartilage, sebaceous glands, ceruminous glands, hair
2/3: bone
EAC boundaries
Ant: Mandibular fossa, parotid
Post: mastoid
Sup: Epitympanic recess (medial), cranial cavity (lateral)
Inf: parotid
What bone makes bony canal of EAC
Tympanic portion of T bone: ant, floor, & part of post
Squamous: rest of post, roof
Epitympanum boundaries
Med: LSCC, CN7 Sup: Tegmen Ant: zygomatic arch Lat: Squamous tbone (scutum) Inf: fossa incudis Post: aditus
Tympanic cavity boundaries
Roof: tegmen
Floor: jugular wall & styloid prominence
Post: mastoid, stapedius, pyramidal prominence
Ant: carotid wall, eustachian tube tensor tympani
Med: labyrinthine wall
Lat: TM, scutum (laterosuperior)
How is the auricle attached to the head?
- Skin
- An extension of cartilage to EAC cartilage
- Ligaments
- Ant lig: zygoma to helix & tragus
- Sup lig: EAC to spine of helix
- Post lig: mastoid to concha - Muscles: ant, sup, and post auricular muscles
Notch of Rivinus
The notch on the squamosa, medial to which lies Shrapnell’s membrane.
The tympanic ring is not a complete ring, w/ the dehiscence superiorly
Shrapnell’s membrane
Par’s flaccida
Meckel’s cave
The concavity on the sup portion of the temporal bone in which the gasserian ganglion (V) is located
Dorello’s canal
B/w the petrous tip and the sphenoid bone
The groove for CN VI
Gradenigo synd
2/2 to petrositis w/ involvement of CN VI
- Pain behind the eye
- Diplopia
- Aural discharge
Macewen’s triangle
Suprameatal triangle
Posterior and superior to EAC
Bound at the meatus by the spine of Henle (otherwise called the suprameatal spine)
This approximates the position of the antrum medially.
Tegmen mastoideum is the thin plate over the antrum
Trautmann’s triangle
Demarcated by the bony labyrinth, the sigmoid sinus, and the superior petrosal sinus or dura
Citelli’s angle
The sinodural angle
Located b/w the sigmoid sinus and the middle fossa dura plate
Others consider the superior side of Trautmann’s triangle to be Citelli’s angle
Solid angle
angle formed by the 3 SCCs
Scutum
Thin plate of squamousa bone that constitutes the lateral wall of the epitympanum
Mandibular fossa boundaries
zygomatic, squamosa, & tympanic bones
Huguier’s canal
Transmits the chorda tympani out of the t bone anteriorly
Is lateral to the roof of the protympanum
Huschke’s foramen
Located on the anterior tympanic plate along a nonossified portion of the plate
Near the fissures of Santorini
Porus acusticus
The “mouth” of the IAC
The canal is divided horizontally by the crista falciformis
3 parts of the inner ear
- Pars superior: vestibular labyrinth (utricle and SCCs)
- Pars inferior: cochlea and saccule
- Endolymphatic sac and duct
4 small outpocketings from the perilymph space
- Along the endolymphatic duct
- Fissula ante fenestram
- Fossula post fenestram
- Periotic duct
4 openings into the t bone
- IAC
- Vestibular aqueduct
- Cochlear aqueduct
- Subarcuate fossa
Ponticulum
Ridge of bone b/w the oval window niche and the sinus tympani
Subiculum
Ridge of bone b/w the round window niche and the sinus tympani
Korner’s septum
Separates the squamosa from the petrous air cells
Scala communis
Where the scala tympani joins the scala vestibuli
The helicotrema is at the apex of the cochlea where the two join
Petrous pyramid
Strongest bone in the body
IAC diameter
8 mm is the upper limit
Cochlear aqueduct
Bony channel connecting scala tympani of the basal turn with the subarachnoid space of the posterior cranial cavity
Avg length in adults in 6.2 mm
Tympanic plexus
= V3, IX, and X
V3 –> auriculotemporal n
IX –> Jacobson’s n
X –> Auricular n
Outer ear blood supply
Posterior auricular art
Superficial temporal art
(Both from ECA)
Foramen of Huschke
The incomplete ossification of the anterior bony canal produces an opening into the infratemporal region called this. Means of extension of malignancy to deep lobe of parotid.
Fissures of Santorini
Naturally occurring defects in the cartilaginous portion of EAC. Provide avenue of spread to superficial parotid
Pyramidal eminence
Pyramidal projection of bone in the posterior mesotympanum from which the stapedial muscle originates
Cochleariform process
Bone in the anterior mesotympanum that anchors the tensor tympani muscle which turns 90 deg and becomes a tendon that connects to the malleus
Ponticulus
Ridge of bone between round and oval windows
Subiculum
Ridge of bone just anterior to round window
Embryologic origin of ossicles
Attic portion are from 1st branchial arch
Mesotympanum portion are from 2nd branchial arch
Stapes footplate is from the otic capsule (primordial otocyst)
Where does the chorda tympani exit the middle ear?
Petrotympanic fissure
What are the branches off the facial nerve within the temporal bone?
- GSPN
- Stapedial
- Chorda tympani
Function of chorda tympani
- Taste to ant 2/3 tongue
2. PARA to submandibular and sublingual glands
Function of GSPN
PARA to lacrimal and minor salivary glands of nose
Facial recess
Space medial to the end of the posterior ear canal but lateral to the vertical segment of CN VII
Sinus tympani
The space medial o the vertical segment of CN VII. This is posterior to the posterior crus of the stapes
Ampullopetal endolymph flow
Displacement of the cupula towards the vestibule provides an excitatory response.
Occurs in the HSCC.
The kinocilium are this oriented towards the utricle side
Ampullofugal endolymph flow
Displacement of the cupula towards the canal provides an excitatory response.
Occurs in SSCC and PSCC.
Thus, the kinocilia are oriented towards the canal side.
Stria vascularis
Forms the outer wall of the scala media and sits within the spiral ligament.
Highly vascular and metabolically active because its job is to create the high potassium concentration of the scala media.
Acts as the battery whose electrical current powers hearing.
Outer hair cell function in the cochlea
Amplifier
Uses electromotility to elongate and shorten in response to receptor potential generated by stereocilia
This generates sound (OAE)
This refines the sensitivity and frequency selectivity of the mechanical vibrations of the cochlea.
