Ear Flashcards
External ear is composed of and does
- Auricle (pinna)
- External acoustic meatus
- Tympanic membrane
- Helps gather sound and direct it to tympanic membrane
Structures of auricle 6
- Helix
- Antihelix
- Concha
- Tragus
- Antitragus
- Intertragic notch
- Used as landmaek in intraoral injections
Sensory Innervation of Auricle
- Superficial Auricle
- Auriculotemporal of V3
- Cervical plexus
- Lesser Occipital n C2
- Greater Auricular n C2, C3
- Deep Auricle
- Auricular branch of CN X
- Auricular branch of CN VII
Arterial supply of external ear
4
- Superficial temp (ECA)
- Posterior auricular (ECA)
- Deep auricular a (Max a.)
- Anterior tympanic (maxillary a.)
External Acoustic Meatus
Made up of
Structures
Innervation
- Auricle to tympanic membrane
- Lateral 1/3, catilaginous
- Medial 2/3 ossous (temporal bone)
- Ceruminous glands (oil glands)
- Cerumen (ear wax)
- Sensory Innervation
- Auriculotemporal of V3
- Auricular branches of
- CN X
- CN VII
Tympanic membrane
membranes
- Seperates external and middle ear
- 3 layered membrane
- External layer is skin, stratified squamous epithelium
- Middle layer is fibrous, attaching to malleous
- Inner layer is mucous membrane, ciliated columnar epithelium
Tympanic Membrane
Innervation
- Sensory innervation
- Outer surface, auriculotemporal of V3
- Inner surface, CN IX
Middle ear
- Air filled cavity
- Transmits sound vibrations from the tympanic membrane
- Lined by mucous membrane
- Located in the petrous portion of the temporal bone
Contents of middle ear
Bones
- Auditory ossicles, lateral to medial
- Malleus
- Incus
- Stapes
Contents of middle ear
Muscles
Spans from
Nerve
Action
- Stapedius muscle
- From pyramid of mid ear to stapes
- Nerve to stapedius of CN 7
- Dampens excessive sound vibrations
- Tensor tympani muscle
- Auditory tube to malleus
- Tenses tympanic membrane, dampens sound
- Tensor tympani nerve of V3
Contents of middle ear
Nerves
- CN VII
- Chorda tympani passes through does not innervate
- Nerve to stapedius
- CN IX
- Tympanic nerve
- Typanic plexus- with sympathetic fibers
- Lesser petrosal nerve
Middle ear
Roof
Floor
- Roof
- Tegmen tympani, seperating middle ear from temporal lobe of the brain
- Floor
- Thin bne, immediately superior to internal jugular vein
- Tympanic canaliculus, tympanic branch of CN IX
Boundaries of middle ear
Anterior wall
- Auditory tube
- Pharyngotypanic or Eustachian tube
- Connects middle ear to nasopharynx, equalizes pressure
- Innervated by tympanic plexus from CN IX
- Lesser petrosal n
- Postganglionic sympathetic fibers
- Wrapped around the internal carotid artery as they travel through the head
- Caroticotympanic nn
Middle ear
Posterior wall
- Facial canal, terminates at stylomastoid foramen, CN 7
- Mastoid antrum, leads to mastoid air cells
- Mastoid canaliculus, auricular branch of CN X
- Stapedius
- Attachment called pyramid
- Attached to stapes
- Nerve to stapedius from 7
- Dampens excessive sound
Middle Ear
Medial wall contents
- Promotory
- Protuberance created by cochlea
- Typanic plexus
- Oval window
- Attachment for stapes
- Round window
- Pressure release for cochlea
- Tensor tympani
- Attached to malleus
- Nerve to medial pterygoid of V3
Middle ear
Lateral wall
- Seperates mid rar and external ear
- Tympanic membrane
- Chorda tympani lies along tympanic membrane
Arterial supply of middle ear
3
Anterior tympanic artery
Stylomastoid artery
Labryrinthine artery
Sensory Innervation of middle ear
Tympanic Plexus of CN 9
Middle ear
Mastoid region
Pharyngotympanic tube
Inner ear: Osseus Labyrinth
portion of
Connects
3 parts
filled with
- Petrous portion of temporal bone
- Connects to the middle ear at oval and round windowa
- 3 parts
- Vestibule
- Semicircular canals
- Cochlea
- Filled with perilymph
Vestibule
Contains
Detects
Contains Utricle and sacculae
Detects linear acceleration and pull of gravity
Senses equilibrium
Semicircular canals
Detects
Hair cells dtect angular/rotational acceleration and decceleration
Senses equilibrium
Cochlea
Contains
Allow for
Senses
Contains cochlear duct
Spiral like seashell
Opening allows perilymph to drain into CSF
Senses audition
Membranous Labryinth
Contains
filled with
4 parts
- Contains hair cells
- Filled with perilymph
- 4 parts
- Cochlear duct
- Sacculae
- Utricle
- Semicircular ducts
Cochlear duct
Spiral structure within cochlea
Roof- Vestibular membrane
Floor- Basilar membrane
Sacculae
Within vestibule
Sensory receptors (maculae)
Utricle
Within vestibule
Sensory receptos maculae
Semicircular ducts
Within semicircular canals
Opens to utricle
Sensory receptors (crista)
CN 8
Travels
branches
- Travels through internal acoustic meatus with CN 7
- In meatus divides into vestibular and cochlear branches
What do CN 8 branches innervate
- Vestibular branch
- Superior
- Sacculae, utricle, semicircular canals
- Inferior
- Sacculae, semicircular ducts
- Superior
- Cochlear branch
- Spiral organ or corti
Cochlea contains 3
- Scala vestibuli
- Perilymph
- Cochlear duct
- Endolymph
- AUditory receptor of linear ear
- Hair cells
- Scala tympani
- Perilymph
Spiral organ of corti
- Basilar membrane
- Hair cells
- high frequency displaces membrane
- Low frequency stimulates apex of cochlea
- Tectorial membrane
