Flashcards in Anatomy - EAR Deck (142):
What embryologic structures is the auricle developed from?
The hillocks of His.
How many hillocks are there and which branchial arches do they arise from?
Six; the first three arise from the first arch and the last three arise from the second arch.
What does each hillock become?
1. Tragus. 4. Antihelix.
2. Helical crus. 5. Antitragus.
3. Helix. 6. Lobule and lower helix.
How does a preauricular sinus tract form?
From improper fusion of the 1st and 2nd branchial arches.
When does development of the extemal auditory canal (EA.C) begin?
The canal begins to develop at 28 weeks gestation.
At what month(s) gestation does the ear canal open?
At what age does the EAC reach adult sizd
What is the signi6cance of a congenitally malformed auricle?
The auricle develops early, making malformations of the middle ear, mastoid, and VII more likely.
Which ossides develop &om the 6rst branchial arch (Meckel's cartilage)?
Head and neck of the malleus, body, and short process of the incus.
Which ossicles develop &om the second branchial arch (Reichert's cartilage)?
Manubrium of the malleus, long process of the incus, and stapes (except footplate).
What does the stapes footplate develop from ?
Which ossicular component develops &om membranous bone?
Anterior process of the malleus.
Which ossicular components never completely ossify?
Part of the manubrium and the vestibular portion of the stapes footplate.
When do the ossicles reach adult size and shape?
At the 16th week gestation, they are adult-sized, and by birth, they are adult-shaped.
Why is the development of the bony otic capsule unique?
It is formed from 14 centers of ossification that fuse and leave no suture lines; the centers are formed from cartilage,
but retain no areas of chondral growth. The bone retains its fetal character, with Haversian canals.
When does the otic capsule begin formation?
At 8 weeks, the precursors of the otic capsule are present; at 15 weeks, the ossification centers are present.
When does the otic capsule finish developingl
By 21-24 weeks, it reaches adult size.
What is the last part of the otic capsule to ossify?
Fissula ante fenestrum.
When does the fallopian canal begin developing?
Fifth week gestation; its development is not complete until several years after birth.
What is the last structure of the inner ear to develop?
What does the eustachian tube (ET) develop from?
From the 1st pouch, between the 2nd arch and the pharynx.
Which branchial arch does the tensor tympani muscle arise from?
First branchial arch.
True/False: The tympanic membrane is derived from ectoderm.
False; it is derived from ectoderm, mesoderm, and endoderm.
At what age is the mastoid process completely pneumatized ?
What is the sensory innervation of the auricule?
Greater auricular nerve (C3), auriculotemporal nerve (V3), lesser occipital nerve (C2, 3), auricular branch of the
vagus, and sensory branches of VII and IX.
What is Arnold's nerve?
Auricular branch of the vagus that innervates skin of the external auditory canal and auricle.
What is the foramen of Huschke?
An embryologic remnant that normally obliterates in the anteroinferior portion of the medial bony EAC.
What is the clinical significance of the foramen of Huschke?
Serves as a potential route for spread of tumor from the parotid gland to the temporal bone.
Which wall of the EAC is shorter-the anteroinferior or posterosuperior?
Posterosuperior (approximately 25 mm, whereas anteroinferior wall is 31 mm).
How much of the EAC is cartilaginous?
How much of the ET is cartilaginous?
Where is the tympanic notch of Rivinus?
Superior portion of the tympanic ring (squamous portion of temporal bone).
How does the composition of gas in the middle ear differ from that of room air ?
Lower oxygen level and higher carbon dioxide and nitrogen levels.
What are the layers of the tympanic membrane?
Squamous epithelium, radiating fibrous layer, circumferential fibrous layer, and mucosa.
Which has greater sensory innervation-pars tensa or pars flaccida?
What are the three nerves of the tympanic plexus?
IX (Jacobson's nerve),
Which part of the ossicular chain has the most tenuous blood supply and is most prone to necrosis?
Long process of the incus.
Which part of the malleus articulates with the incus?
Where in the ossicular chain does the tensor tympani muscle insert?
Manubrium of the malleus.
Which part of the malleus does the anterior ligament attach to?
The neck, near the anterior process.
Which part of the incus articulates with the stapes?
Lenticular process (medial side of long process).
What ligament supports the stapes?
Where does most of the movement of the stapes occur
Anterio-superior portion of the footplate
Where in the ossicular chain does the stapedius muscle insert?
posterior neck of stapes
What is the scutum?
Lateral wall of epitympanum
What are the boundaries of the epitympanum?
Superiorly - tegmen tympani
Inferiorly - fossa incudis,
Anteriorly- zygomatic arch
Posteriorly - aditus ad antrum
Medialy - lateral semicircular canal and VII
Which ossicles can be found in the epitympanic recess?
Head of the malleus, body, and short process of the incus.
What is the inferior boundary of the tympanic caYity?
What structures are anterior to the tympanic cavity?
The carotid artery, ET, and the canal for the tensor tympani muscle.
What structures are posterior to the tympanic cavity?
and stapedial tendon
What is the promontory?
Elevation of the medial wall of the tympanic cavity formed by the basal turn of the cochlea
Which three cranial nerves are found beneath the floor of the middle ear caYity?
IX, X, and XI.
What structure is located inferior to the subiculum and posteroinferior to the promontory?
What structure lies between the subiculum and ponticulus?
What structure lies superior to the ponticulus?
What structure lies between the prominence of SCC and the promontory/oval window?
Prominence of the facial canal.
What is the most anterior structure of the medial wall of the tympanic cavity?
What is the most anterior structure of the medial wall of the tympanic cavity?
What structure is situated just medial to the tip of the cochleariform process?
Geniculate ganglion of the facial nerve.
Between which ossicles does the chorda tympani run?
Manubrium of the malleus and long process of the incus.
What is the function of the chorda tympani nerve?
Parasympathetic innervation to the submandibular and sublingual glands, and taste to the anterior 2/3 of the
What structure ends blindly at the round window?
Scala tympani ( lower compartment of the cochlea)
What is the name of the central bony core of the cochlea through which nerves and -vessels travel?
What is the name of the area of communication between the scala vestibuli and the scala tympani?
What fluid surrounds the membranous labyrinth?
How does perilymph differ from endolymph ?
pH of 7.2
High in Sodium
dose not contain chloride
high potassium and chloride
True/False: The membranous labyrinth is a self-contained system.
What are the main structures of the vestibular portion of the membranous labyrinth
Utricule, Saccule, and simicircular canals
Which of these main structures of vestibular portion of membranous labyrith receives the crura from the three SCCs
What structures house the crista
What is the blood supply to the inner ear?
(branch of inferior cerebral artery)
What structure produces endolymph
Where does most of the resorption of endolymph occur?
What does the vestibular aqueduct carry?
Endolymphatic duct and accompanying vein
Where is the primary auditory cortex?
Brodmann's area 41 in the superfacial portion of the temporal lobe
Which part of the vestibular labyrinth detect angular acceleration?
What do the utricle and saccule detect?
Where are cupula found?
What three systems determine balance?
vestibulo-ocular (visual), vestibulospinal (proprioceptive) systems
Which part of the cochlea represents high-frequency sounds?
The basal end
What range of frequencies can the human ear detect?
20-20,000 Hz (greatest sensitivity is from 500 to 3000 Hz)
What noise level begins to cause pain?
How many times louder is 60 dB than 0 dB?
What are normal ear canal volumes in children and adults?
children : 0.5-1.0 cm
adults : 0.6-2.0 cm3
Which cells emit otoacoustic emissions (OAEs)?
outer hair cells
What percent of normal ears emit spontaneous OAEs?
What are the four parts of the temporal bone?
What are the four openings into the temporal bone?
internal auditory canal
What is Hyrtl's fissure?
Connection between the subarachnoid space near the IX ganglion and the hypotympanum that allows middle ear
infections to spread to the brain; normally closes with maturation.
What proportion of the population has a pneumatized petrous pyramid?
What is Trautmann's triangle?
Triangle between the external prominence of the lateral and posterior SCCs and the posterosuperior corner of the
What is Körner's septum?
Otherwise known as the "false bottom," it represents the suture line between the petrous and squamous portions of
the temporal bone.
What is meant by a "diploic mastoid"?
Occupied by bone marrow instead of air cells.
What structure forms the arcuate eminence?
True/False: The position of the cochlear duct is always inferior to the lowest border of the stapes
Besides the muscles of facial expression, what muscles does the facial nerve innervate?
posterior belly of digastric muscle
What does the facial nerve provide general sensation for?
part of the auricular concha, external auditory canal, tympanic membrane
What is the function of the special visceral afferent fibers of the facial nerve?
provide taste to the anterior 2/3 of the tongue and the palate
Where are the cell bodies for the afferent fibers of the facial nerve?
What is the function of the nervus intermedius?
To carry visceral motor fibers to the lacrimal gland, minor salivary glands, and mucosal glands of the palate and nose (via the greater superficial petrosal nerve), and general sensory fibers from the auricular concha and external
Whats nervus intermedius
nervus intermedius, also known as intermediate nerve of Wrisberg, is a part of the facial nerve (CN VII) which contains somatic sensory, special sensory, and visceral motor (secretomotor) fibres
What are the six segments of the facial nerve?
Internal audiotory canal
where in the brainstem is the facial nerve motor nucleus
Where dose the facial nerve leave the brainstem
Pontomedullary junction, close to the vestibulocohlear nerve
What are the limits of the tympanic segment ofVII
Geniculate ganglion to the 2nd genu (adjacent to the pyramidal process)
What are the limits of the mastoid segment of VII?
Pyramidal process to the stylomastoid foramen
What segment of the facial nerve is the shortest
What portion of the facial nerve is closest to cochlea ?
What three branches of the facial nerve are given off in its course through the temporal bone?
Greater superficial petrosal nerve, nerve to the stapedius muscle, and chorda tympani.
What is the first branch of the facial nerve
Greater superfacial pertosal nerve
Where along the course of the facial nerve does the greater superfacial petrosal nerve branch off
What is the blood supply to the geniculate ganglion?
Greater superfacial petrosal artery (branch of middle meningeal artery)
What is the function of the greater superficial petrosal nerve?
Lacrimation, salivation from minor salivary glands, and mucosal secretion from nose and palate
Where do the preganglionic puasympathetic neurons of the greater superficial petrosal nerve synapse?
Branches of which nerve then carry the postganglionic parasympathetic neurons to the mucus-secreting
glands in the nose, sinuses, and palate?
Maxillary division of the trigeminal nerve
What is the facial hiatus?
Dehiscence of variable size in petrous portion of the temporal bone in the floor of the middle cranial fossa, which
marks the entrance of the greater superficial petrosal nerve into the middle cranial fossa.
How is the facial hiatus clinically significant
The geniculate ganglion usually lies deep to the hiatus, but in 5-10% of patients, it lies under the dura within the
hiatus and without a bony covering.
What are the limits of the fallopian canal
Fundus of the lAC to the stylomastoid foramen.
Describe the path of the facial nerve in the temporal bone.
Enters the lAC; travels laterally for a short distance, then, just superior to the promontory, it makes a sharp turn to run posteriorly (at the external first genu and the geniculate ganglion). Nerve continues posteriorly, with a slight inferolateral inclination (forming the prominence of the facial canal in the medial wall of tympanic cavity). Behind the base of the pyramidal eminence, the nerve makes a broad turn to descend vertically and somewhat laterally (2nd
genu) through the mastoid cavity.
What is the average diameter of the lAC?
What is the upper limit of normal diameter of the lAO
What is the narrowest intratemporal portion of the fallopian canal?
Entrance to the fallopian canal at the lateral aspect of the lAC (fundus).
What structure bisects the lAC in the vertical direction and in the horizontal direction?
Bill's bar - vertical
transverse/falciform crest- horizontal
What does the superior vestibular nerve innervate?
Superior and lateral SCCs, utricle, and saccule.
What does the inferior vestibular nerve innervate?
Posterior SCC and macula of the saccule.
Where is the 2nd genu of the facial nerve
Just distal to the geniculate ganglion, at the sinus tympani between the tympanic and mastoid segments.
What is the relationship of the 2nd genu of the facial nerve to the lateral SCC and short process of the incus
Inferior to the lateral SCC and medial to the short process of the incus.
In its tympanic segment, between which structures does the facial nerve travel
superiorly -lateral SCC
inferiorly - the oval window
Where does the facial nerve lie in relation to the cochleariform process
What is the cog?
A ridge of bone that extends inferiorly from the tegmen epitympanum and partially separates the anterior
epitympanic compartment from the mesoepitympanum.
What is the relatiotship of the tympanic portion of VII to the cog?
VII lies anterior to the cog in the floor of the anterior epitympanum.
What percent of people have a dehisunce of the facial nerve in either the tympanic or mastoid segments?
Where is the most common site of dehiscence of facial nerve
tympanic segment superior to oval window
What is the last branch of the facial nerve before it passes through the stylomastoid foramen?
Where does the chorda tympani arise in relation to the stylomastoid foramen?
usually 4-7 mm superior
What artery accompanies the chorda tympani?
posterior tympanic artery
What is the name of the opening through which the chorda tympani nerve enters the infratemporal fossa?
petrotympanic fissure (canal of Huguier)
Where are the cell bodies of the motor fibers of the chorda tympani nerve
superior salivatory nucleus
What three motor branches does the facial nerve give off just after exiting the stylomastoid foramen?
n. to posterior belly of digastric
n. to stylohyoid
n. to postauricular m.
Where is the facial nerve trunk located in relation to the tympanomastoid suture line?
6-8 mm aterioinferior (between the suture line and the styloid prosess)
What is the name of the point at which the facial nerve divides into the upper and lower divisions?
How far is the pes anserinus from the stylomastoid foramen
approximately 1.3 cm