Temporal Bone Flashcards
The adult temporal bone is made up of five bony parts. What are these parts?
Squamous, mastoid, petrous, tympanic, and styloid portions
What is the function of the squamous portion?
This functions as the bony floor of the adult suprazygomatic masticator space (i.e., temporal fossa) and the lateral wall of the middle cranial fossa
What are the three important landmarks of the mastoid portion?
Mastoid antrum
Aditus ad antrum (Latin for “entrance to cavity”)
Korner septum
What is the purpose of the aditus ad antrum?
It connects the epitympanum (i.e., attic) of the middle ear cavity to the mastoid antrum.
What is the Korner’s septum?
It is a part of the petrosquamosal suture that runs posterolaterally through the mastoid air cells.
What is the function of the Korner’s septum?
It acts as a barrier to extension of infection from the lateral mastoid air cells to the medial mastoid air cells.
It also functions as an important surgical landmark within the mastoid air cells.
The inner ear is contained within what portion of the temporal bone?
Petrous portion
It is often referred to as the petrous pyramid
What are the two important structures on the anteior surface of the petrous pyramid?
The tegmen tympani - roof or cover of the tympanic cavity
The arcuate eminence - bone prominence over the superior semicircular canal. This is a surgical landmark as the surgeon cuts along the floor of the middle cranial fossa.
The posterior surface of of the petrous portion of the temporal bone contains what structures?
The porus acusticus - opening (or “mouth”) of the internal auditory canal
Modiolus (Latin for “hub”) - which is the entrance to the cochlea through which the cochlear nerve passes, and the crista falciformis, which is the horizontal bony septum in the lateral 3 mm of the internal auditory canal
Vestibular aqueduct - transmits the endolymphatic duct and runs parallel to the line of the petrous ridge
Cochlear aqueduct - transmits the perilymphatic duct and located vertically below the internal auditory canal running parallel to it
What is the function of the inferior surface of the petrous temporal bone?
It helps to form the carotid canal and jugular foramen
The petrous apex is seperated from the clivus by what structures?
By the petrooccipital fissure and the foramen lacerum
This portion of the temporal bone is a U-shaped bone forming the majority of the adult bony external auditory canal.
Tympanic portion
This portion of the temporal bone forms the styloid process.
Styloid portion
Like the mastoid process, the styloid process develops after birth.
The medial border of the external auditory canal is form by what structure?
Tympanic membrane
This is the bony projection to which the tympanic membrane attaches superiorly; it attaches to the tympanic annulus inferiorly.
Scutum
This is an important landmark to determine if a lesion is in the external or middle ear.
Tympanic annulus
Where is the nodal drainage of the external auditory canal and adjacent scalp?
Parotid lymph nodes
What are the three distinct regions of the middle ear?
Epitympanum or attic
Mesotympanum or tympanic cavity proper
Hypotympanum
What are the six important walls of the normal middle ear cavity?
A. Anterior wall, or "carotid wall" B. Posterior wall. or "mastoid wall" C. Superior wall or tegment tympani D. Inferior wall or "jugular wall E. Lateral wall, or "membranous wal"
The upper part of the posterior wall of the middle ear is absent. What connects the epitympanum to the mastoid antrum?
Aditus ad antrum
The lower part of the mesotympanic portion of the posterior wall is comprised of three important structures. What are these structures?
Pyramidal eminice
Sinus tympani
Facial nerve recess
This is the tympanic cavity above the line drawn between the inferior tip of the scutum and the tympanic portion of the facial nerve.
Epitympanum
What are the contents of the epitympanum?
The malleus head and the body and short process of the incus.
This is the area between the incus and the lateral, side wall of the epitymopanum.
Prussak’s space
This is the tympanic cavity or cleft proper. It extends from the inferior tip of the scutum above the line drawn parallel to the inferior aspect of the bony external auditory canal.
Mesotympanum
What are contents of the mesotympanum?
Remainder of the osscicles
- Manubrium of malleus, the long process of the incus, and the entire stapes
Two muscles of the middle ear
- Tensor tympani and stapedius muscle
This is a shallow trough in the floor of the middle ear.
Hypotympanum
What are the contents of the hypotympanum?
The hypotympanum contains no vital structure
This region of the ear contains the membranous labyrinth, which is set within the bony labyrinth (i.e., otic capsule)
Inner ear
The membranous labyrinth consists of what structures?
Vestibule (i.e., utricle and saccule) Semicircular channels Endolymphatic duct Cochlear duct Multiple communicating channels
The bony labyrinth forms what structures?
The cochlea, vestibule, semicircular canals, and both the vestibular and cochlear aqueducts
The cochlea has approximately how many turns?
Two and one-half turns
The basal first turn and the apical second turn are readily visible on routine CT scansof the temporal bone.
The basal first turns opens posteriorly into the round window niche.
The entire cochlea encircles a central bony axis, also called the modiolus. The cochlear nerve enters the cochlea through the modiolus on its way to the multiple spiral ganglia.
This is the largest part of the membranous labyrinth.
The vestibule
It is the more cephalad portion of the vestibule.
The utricle
The saccule is the inferior part.
The vestibule is separated laterally from the middle ear by what structure?
Oval window niche
Superiorly, the vestibule leads to where?
Superior semicircular canal
Medially, this structure separates the vestibule from the fundus of the internal auditory canal.
Lamina cribrosa
The upper bony margin of the superior semicircular canal forms a convexity on the petrous pyramid roof, called what?
Arcuate eminence
The midtympanic portion of the facial nerve passes along the undersurface of the what part of the semicircular canal?
Lateral semicircular canal
The cochlear aqueduct contains what?
The perilymphatic duct
This structure encompasses the endolymphatic duct.
The vestibular adqueduct
What are the segments of the facial nerve within the temporal bone?
Cisternal segment: Facial nerve from brain stem to porus acusticus
Internal auditory canal segment: Facial nerve in the anterosuperior portion of the canal
Labyrinthine segment Short segment of facial nerve curling anteriorly over the top of the cochlea.
Tympanic segment Facial nerve from anterior genu to posterio genu.
Mastoid segment: Facial nerve from posterior genu to stylomastoid foramen
Parotid segment: Extracranial segment of the facial nerve
What are the four major functions of the facial nerve that may be used to localized topographically a lesion along its course?
From central to peripheral:
- Lacrimation (via greater superficial petrosal nerve)
- Stapedius reflex - sound dampening
- Taste, anterior two thirds of the tongue (via chorda tympani to lingual nerve to oral tongue)
- Facial expression
