Histology of the Ear Flashcards
What are the three general ear components?
external ere, middle ear, inner ear
What are the two functions of the ear?
hearing and balance
What are the components of the external ear? What is it made of?
the auricle (helix, antihelix, tragus, antitragus)
elastic cartilage core, except for lobule which is mostly connective tissue
What is the support for the external dutiory meatus?
elastic cartilage for outer 1/3 and temporal bone for the inner 2/3
What two glands work together to form cerumen (ear wax)?
sebaceous and ceuminous glands
What separates the external and middle ear?
the tympanic membrane
FOr the tympanic membrane…
what is the outer surface made of? The core? the inner surface?
outer surface = thin sin
core = two layer sof fibro-elastic connective tissue
inner surface = simple squamous epithelium
What structures make up the middle ear?
the tympanic cavity with the ossicles (malleus, incus, stapes)
auditory (eustachian) tube
How does the histology of the auditory tube change as it goes from bony portion to pharyngeal opening?
bony: low columnar epithelium with cilia
carilaginous: pseudostratified epithelium with some goblet cells near pharyngeal opening
What sort of epithelium covers the ossicles?
simple squamous epithelium
What are the two muscles of the middle ear?
stapedius and tensor tympani
If the malleus communicates with the tympanic membrane, what does the stapes communicate with?
the membrane over the oval window
What are the two “sections” of the inner ear?
the bony labyrinth and then the membranous labyrinth suspended in the bony
Starting from the oval window, what are the portions of the osseous labyrinth?
oval window opens into the vestibule
semicircular canals
ampullae of each canal
cochlea with modiolus and spiral lamina
vestibular aqueduct
What are the two openings of the vestibule?
oval window (with base plate of stapes)
round window
HOw many semicircular canals are there?
6 - three on each side
superior, posterior, lateral
What are the ampullae?
they are dilations at the ends of each semicircular canal
THe cochlea is a spirally coiled tube like a snail shell in the shape of a cone - what is the bony axial stem called?
the modiolus
WHat is the bony, shelf-like projection which spirals around the modiolus liek threads on a screw?
the spiral lamina
What kind of bone is the oseeous labryinth carved out of?
compact bone - covered by periosteum and then simple squamous epithelium
What fluid fills the osseous labyrinth?
perilymph
What are the two chambers of the vestibule?
the utricle (upper posterior location)
and the saccule *(ower anterior position - smaller)
Of the utricle and the saccule, which communicates with the semicircular canals and which communicates with the cochlea?
the utricle communicates with the canals and the saccule communicates with the cochlea
What is the receptive area in the utricle called? The saccule
they are both macula
so the macula utriculi and macula succuli
What is the receptive area of the ampulas?
the cristae ampularis - one for each ampulae
What joins the utricle and saccule together?
the y-shaped tube containing the endolyphatic, utricular and saccular ducts
What do the non-receptive areas of the inner ear look like histologically?
simple squamous epithelium with a basal lamina
What are the two general cell types found in the receptive areas of the inner ear?
the sustentacular cells (supporting cells)
Hair cells (the sensory neuroepitheliual cells)
What are the two types of hair cells?
type 1 and type 2
In what ways are the two hair cell types similar?
they both have 30-100 long microvilli, arranged by length
all have one kinocilium (but lose it in the auditory system)
have both afferent and efferent innervation in some way or another
How do the type 1 and type 2 hair cells differ?
shape: type 1 are more globular, type 2 more cylindrical
type 1 hair cells are always located at the border of a cell
type 1 cells have more afferents (since they’re the main sensory cells) while type 2 cells have more efferents (since they’re more the contractile cells of the system)
type 1 cells receive their afferents as a sort of cup while the efferents contact the afferent nerve endings instead of the cell itself
type 2 cells receive their afferents and efferents directly on the cell surface
What is the gelatinous membrane of the maculae called?
the otolithic membrane
What is the relationship between the sterocilia of the hair cells and te otolithic membrane?
the cilia are embedded in it
What are otoconia?
they are crystals of calcium carbonate and protein embedded on the surface of the otolithic membrane
What is the gelatinous membrane of the cristae ampullae (the cristae equivalent of the otolithic membrane)?
the cupula
more of a cone shaped area - cilia still embedded init
What two membranes subdivide the bony cochlea into three cavities?
Basilar membrane (also supports organ of corti)
vestibular membrane
What are the three cavities of the cochlea?
scala vestibuli - upper
scala tympani - lower
cochlear duct (or scala media)
Which cavities have perilymph and which has endolymph?
the vestibuli and tympani have perilymph
the cochlear duct has endolymph
At what point are the scala vestibuli and scala tympani continuous with each other?
the helicotrema
What is the cecum cupulare?
it’s the blind end of the cochlear duct at the apex of the cochlea - it’s not open so endolymph can’t leave at that point
Where is the helicotrema located?
at the apex of the cochlea
What is the limbus spiralis?
it is an area of thickening periosteum just aboe the spiral lamina
it bulges into the cochlear dict
the lower part is continuous with the basilar membrane
What are the main supporting cells of the organ of corti?
the inner and oute rpilar cells form an intervening tunnel while the inner and outer phalangeal cells surround the support the hair cells
Describe the two sets of hair cells in the organ of corti?
the inner hair cells are type 1 cells - only 1 row
the outer hair cells are type 2 cells = the number of rows bary depending on wher eyou are in the organ of corti
How many rows of outer hair cells are there in the different regions of the cochlea/
basal coil = 3 rows (high pitches)
second coil = 4 rows
upper coil = 5 rows (low pitches)
How is the manner in which the phalangeal cells surround the type 1 and type 2 hair cells different? Why is this significant?
The type 1 cels are wrapped tightly intot he inner phalangeal cells
the type 2 cells are wrapped losely in between the outer phalangeal cells, so there is a space
this is significant because the type 2 cells have contractile capabilities and the space allows them to do so
What is the ribbon of relationous material that rests upon the hair cells in the organ of corti?
the tectorial membrane
What ganglion is located at the junction of the osseous spiral lamina and modiolus?
the spiral ganglion
What types of neuron cell bodies are contained in the spiral ganglion?
bipolar neurons (with myelinated central processes and unmyelinated “dendrites” reaching to the hair cells in the organ of corti)
How is the composition of endolymph and perilymph different?
endolymph: high K+ and low Na+ (like intracellular fluid)
lerilymph: looks like extracellular fluid
What produces the endolymph?
the stria vascularis probably (on the lateral wall of the cochlear duct)
What absorbs the endolymph?
the endolymphatic duct
In what ganglion are the cell bodies of the vestibular nerve afferents?
the vestibular ganglion in the internal auditory meatus of the temporal bone
THe vestibular nerve divides into a seuprior branch and an inferior branch - what do they supply?
superior = horixontal crita ampularis, superior crita ampullaris, macula utriculi, and msall part of th emacula sacculi
inferior: posteiro rcrita ampullaris and major portion of the macula sacculi
