EXAM 3 - EAR 17 Flashcards
What is the histology of the auricle?
It is the pinna of the ear and the auditory canal
integument overlying elastic cartilage integument is thin, keratinized stratified squamous epithelium hair follicles
hair follicles can be observed in the dermis
What is the histology of the auditory meatus
Outer third of ear canal is elastic cartilege
inner 2/3 is bone
Lining of ear canal is stratified squamous eoithelium with sebaceous glands and ceruminous glands
What is the histology of the tympanic membrane?
“Ear drum”
core is formed vascularized innervated connective tissue
external surface covered by thin skin
internal surface by simple cubodial epithelium
What are the three auditory ossicles and how do they relate to each other?
- Malleus (hammer)
- attaches to the tympanic membrane
- articules with incus (Anvil)
- Incus (anvil)
- intermediate bone b.w the stapes and the malleus
- Stapes
- Shaped like a stirrup due to opening for stapedial artery
- inserts onto oval window
What are the two openings in the middle ear and how does it relate to the inner ear?
- Oval window
- the stapes ataches to the memnrame covering oval window
- oval window opens into the scala vestibuli
- ROund window
- membrane covered region is at the end of the scala tympani
What are the two muscles of the middle ear?
- Tensor tympani
- Inserts on the malleus
- Stapedius
- inserts on the stapes
- These muscles contract reflexively in response to loud sounds inorder to dampen the vibrations of the auditory ossicles
What are the four regions of the inner ear?
Boney labyrinth
membranous labryrinth
vestibular organ
auditory organ
What is the bony labyrinth?
- System of canals and chambers embedded in the petrous portion of the temporal bone
- Filled with high sodium content perilymph
- Consists of Semicircular canals
- cochlea
- scala vestibuli
- scala tympani
What is the membranous labyrinth
- System of membranous structures embedded within the chambers of the bony labyrinth
- Filled with high potassium content endolymph
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What are the vestibular organs ?
- Patches of sensory structures that resond to changes in position
- Consists of
- maculae of saccule and utricle
- cristae ampullaris of semcircular canals
What is the structure of the maculae in relation to the epithelum, hair cells, and otolithic membrane and how does it compare to the cristae ampullares?
- Epithelium
- columnar supporting cells
- vestibular hair cells
- numerous sterocilia
- single kenocilium ( single longer brissle)
- Hairs cells are in contact with afferent nerve endings
- Otolithic membrane
- geletinous layer containing calcium carbonate crystals (otolithics) that over lies epithelium
- Sterocilia of bestibular hair cells are embedded in this gelatinous layer
- movements of head displaces the otolithic membrane and casuses sensory impulse. ( via displacement of mebrane potential in hair cells)
What is the histological structure of the cochlea (auditory organ)
- Cochlear duct (scala media : high K+ ) divdeds the bony cohlea into
- scala vestibuli (high Na+)
- scala tympani (high Na+)
- huge potential difference creates high sensitivity
- VEstibular membrane
- forms the roof of the duct
- Basilar membrane
- forms the floor of the duct
- Stria vascularis
- forms the lateral aspect of the duct
- particpates in the formation of endolymph
- Organ of Corti
- Lies on basilar membrane
How does the cristae ampullares differ from the masculae of saccule and utricle
- Pretty much same as it except….
- Cupla instead of membrane
- geletinous layer similiar to otolithic membrane but without otoliths
- movement of ehad creates shear forces b/w semi circular canals and the contained fluid
- movement displaces the cupla and causes the sterocilia to bend
- for dynamic movements like turning head left and right
