SM_26b: Ear Structure and Function Flashcards
Describe the parts of the temporal bone
Temporal bone
Auditory (pharyngotympanic) canal is for the ____ tube
Auditory (pharyngotympanic) canal is for the auditory / Eustachian tube
- Connects nasopharynx with middle ear
- Parallel to anterior border of the petrous part of the temporal bone
Petrous part of temporal bone separates ____ and ____
Petrous part of temporal bone separates middle and posterior cranial fossae
- Features: upper sigmoid sinus, greater and elsser petrosal grooves, superior and inferior petrosal sinuses
- Greater petrosal sinus points to foramen lacerum -> greater petrosal contributes to petrosal canal
Descirbe temporal bone ossification
Temporal bone ossification
- Petrous and mastoid: cartilage from somite sclerotomes
- Squamous: membrane from 1st pharyngeal arch mesenchyme
- Tympanic: membrane from 1st pharyngeal arch mesenchyme
- Malleus and incus: cartilage from pharyngeal arch 1
- Stapes: cartilage from pharyngeal arch 2
- Styloid process: cartilage from pharyngeal arch 2
First pharyngeal groove forms ___
First pharyngeal groove forms external auditory meatus
(groove is ectoderm)
First pharyngeal pouch forms ____ and ____
First pharyngeal pouch forms auditory tube and middle ear cavity
Otic placode forms ____
Otic placode forms inner ear organs of hearing and balance
Otocyst comes from ____ and shapes into ____ and ____
Otocyst comes from otic placode and shapes into cochlea and semicircular canals
Cartilage of auricle of pina comes from ____ and ____
Cartilage of auricle of pina comes from three swellings of Arch 1 mesenchyme and three swellings of Arch 2 mesenchyme
Middle ear is the ___ and arises from the ___
Middle ear is the tympanic cavity and arises from the 1st pharyngeal pouch
Describe derivatives of each pharyngeal pouch
Pharyngeal pouch derivatives
- Pouch 1: auditory tube, middle ear, mastoid air cells
- Pouch 2: palatine tonsils
- Pouch 3: thymus, inferior parathyroids
- Pouch 4: superior parathyroids, thyroid C-cells
Describe components of the middle ear
Components of the middle ear
- Roof: tegmen tympani (of petrous temporal)
- Floor: jugular bulb
- Anterior: internal carotid artery, auditory tube
- Posterior: facial nerve (VII), mastoid air cells
Three ear ossicles trasmit ____ from ____ to ____
Three ear ossicles trasmit sound vibrations from the tympanic membrane to the inner ear
- Malleus
- Incus
- Stapes
- Oval window
Malleus and incus arise from ____, while stapes arises from ____
Malleus and incus arise from Arch 1 cartilage, while stapes arises from Arch 2 cartilage
Middle ear is connected to the ____
Middle ear is connected to the nasopharynx
(kids have short Eustachian tubes so get ear infections easily)
Describe tympanic membrane color
Tympanic membrane color
- Normal: pearly gray, clear, colorless
- Amber: serous effusion, not infected
- Red: not a good predictor of acute otitis media
- White / yellow: fluid or pus, could be acute otitis media
- Discreet patches of white: sclerosis / scarring of tympanic membrane
- Yellow mass on tympanic membrane: cholesteatoma
Describe membrane position
Membrane position
____ is on oval window
Stapes is on oval window
Inner ear is a ____ in a bony ____
Inner ear is a membranous labyrinth (cochlea and semicircular canals) in a bony labyrinth
- Membranous labyrinth contains endolymph from capillaries and is surrounded by perilymph in bony labyrinth from CSF
- Utricle and saccule register gravity
Saccule senses motion in the ____, while utricle senses motion in the ____
Saccule senses motion in the vertical plane, while utricle senses motion in the horizontal plane
(movement of head in any direction is sensed by saccule and utricle, otolymph bends hair cells)
Endolymph is in the ____ that divides the ____
Endolymph is in the cochlear duct that divides the bony labyrinth
- Sound vibrations in endolymph stimulate hair cells which stimulate cochlear nerve
- Slightest amount of bending opens up channels -> K exchanged for Ca -> Ca causes release of neurotransmitter
Sound vibrations in endolymph stimulate ____ which stimulate the ____
Sound vibrations in endolymph stimulate hair cells which stimulate the cochlear nerve
Sound vibrations pass from oval ____ to ____
Sound vibrations pass from oval to round window
- Vibrations in perilymph extend the length of the cochlear duct: down one side and up the other to the round window
- Adjacent endolymph is stimulated
External auditory meatus receives general sensory innervation from the ____
External auditory meatus receives general sensory innervation from the vagus nerve (X)
Middle ear receives visceral sensory innervation from the ____
Middle ear receives visceral sensory innervation from the tympanic branch of the glossopharyngeal nerve (IX)
Inner ear receives special sensory innervation from the ____
Inner ear receives special sensory innervation from the vestibulocochlear nerve (VIII)
Vagus nerve sends a cutaneous branch with ____ fibers to the external auditory meatus
Vagus nerve sends a cutaneous branch with general sensory fibers to the external auditory meatus
(probing the meatus can produce a cough reflex and a referred vagus sensation of nausea)
Tympanic nerve, which is the pretrematic branch of CN IX (glossopharyngeal), is ____ to the middle ear and ____ to the parotid gland
Tympanic nerve, which is the pretrematic branch of CN IX (glossopharyngeal), is visceral sensory to the middle ear and parasympathetic to the parotid gland
- Parasympathetic to the parotid gland via the auriculotemporal branch of V3
Temporal bone relates parasympathetic paths of the facial nerve: ____, ____, and ____
Temporal bone relates parasympathetic paths of the facial nerve
- Tympanic nerve (IX) to lesser petrosal to V3 to the parotid gland
- Greater petrosal (1) of VII to V2 to lacrimal and nasal / palatal mucosa
- Chorda tympani (2) of VII to lingual nerve (V3) to other salivary glands
Summarize the ear primordia
Ear primordia
- Inner ear from otic placode
- Auricle from Arch 1/2
- Malleus and incus from Arch 1
- Stapes from Arch 2
Indicate primordia for the following
Primordia
