Anatomy and Histology of the Ear Flashcards
External ear is supplied by what artery
Posterior auricular from external carotid, as well as anterior auricular branches from superficial temporal
Innervation to the external ear
Auriculotemporal to anterior external ear
Posterior ear supplied by lesser occipital and greater auricular
Vagus and glossopharyngeal nerve supply the concha/inner bowl of ear
Facial nerve supplies skin over mastoid process
External acoustic meatus innervation
Superior TM supplied by facial
Anterior TM auriculotemporal
Posterior TM great auricular nerve
Inferior/floor of TM Arnolds nerve from vagus
Cough reflex
Efferent- vagus and phrenic
Afferent- vagus
Outer 2/3rds vs inner 2/3rds of EAC
Inner 1/3rd is only skin and bone (only place in body like that)
External 2/3rds have CT and cartilage
Epithelium of TM
Outside layer is stratified squamous
Inside layer is simple cuboidal
Where is the cone of light found in the TM
Inferior/2nd quadrant
Tympanic cavity is located in what bone
In the petrous portion of temporal bone
Chorda tympani runs over what in the middle ear
Runs over the tensor tympani
Anterior, lateral walls and roof/floor of tympanic cavity
Anterior wall- Eustachian tube opening
Lateral wall- tympanic membrane
Floor- jugular wall
Roof- tegment tympani
What sinus runs into tympanic cavity
Sigmoid sinus
Distal 2/3rds and proximal 1/3rd of eustachian tube
Distal 2/3 are cartilage
Proximal 1/3 is bone
What bone is associated with oval window
Stapes
Membranous labyrinth
Made of small sacs and tubes within bony labyrinth
Contains cochlear duct and semicircular ducts with utricle and saccule
Contains sensory cells
Bony labyrinth
Contains cochlea, vestibule and semicircular canals, separated from membranous labyrinth by perilymph
Scala media
Middle compartment of cochlear duct, contains endolymph
Stria vascularis forms the lateral wall and creates endolymph
Scala vestibuli
Contains perilymph, moved by stapes at oval window, continuous with scala tympani
Scala tympani
Connected to round window
Organ of corti composition
On floor of scala media resting on basilar membrane
Composed of hair cells, phalangeal cells (support for hair cells) and pillar cells (support b/w basilar membrane and tympanic lip)
How does organ of corti function
Basilar membrane vibrates with sound causing deflection of stereocilia attached to tectorial membrane, opening K+ channels in hair cells
Inner ear/middle functions
Inner-Responsible for balance, and takes external sound waves and transforms them into usable information for brain
Middle- takes sound waves and turns it into physical movement
Path of sound waves in inner ear
Stapes moves oval window causing fluid pressure wave formation in perilymph
Wave distorts vestibular membrane causing pressure wave within endolymph of scala media
Basilar membrane is displaced, hair cells are distorted, pressure in perilymph is transferred to scala tympani and exits via round window
Semicircular canals
Sense head rotations
Filled with endolymph
Connected to utricle
End of canals have ampulla with gelatinous-like cap called cupulla which has hair cells with stereocilia attached
Utricle
Found inside vestibule
Contains a macula w/hair cells and stereocilia and an overlying otolithic membrane which is covered with calcium carbonate crystals called otoconia
Senses linear acceleration and head tilts in horizontal plane
Which way is forward? u trip forward
Saccule
Also found inside vestibule and has a macule like the utricles
Senses acceleration and head tilts in vertical plane
Which way is up? sack up
What causes depolarization of hair cells
K+ channels opening
Hair cells and kinocilia
Hair cells have stereocilia and the grow in length in a row
Kinocilia is the longest one
If other cilia are deflected towards kinocilium, K+ channels open
Perilymphatic space
Found between bony and membranous labyrinths
Similar composition to CSF
Drains via perilymphatic/cochlear duct into subarachnoid space
Originates from periosteum
Endolymphatic space
High in K+, low in Na+
Originates from stria vascularis
Drains via endolymphatic duct into venous sinuses of dura mater
What type of cartilage is in auricle, and what supplies it with nutrinets
Elastic cartilage, supplied by perichondrium
What happens if perichondrium is sheared off elastic cartilage
Hematoma, necrotic cartilage
Necrotic cartilage results in chondrogenesis
Creates cauliflower ear
What antibiotic should be avoided with TM injury
Gentamicin
Mastoiditis
Infection of mastoid cells
Can spread into cranial fossa via petrosquamous cranial suture
Treated with abx
Menieres syndrome
Associated with increased endolymph volume leading to abnormal signaling
Conductive hearing loss
Effects outer or middle ear- otitis media, excessive wax, otosclerosis
Sensorineural hearing loss
Reduction in sound level and/or fidelity due to damage to inner ear or auditory nerve
Affects hearing at different frequencies and intensities
Age related or noise induced
Central hearing loss
Problem in CNS
