Ear - Downing Flashcards
Histology of utricle, saccule, and semicircular canals
The non-receptive areas will have simple squamous epithelium with a basal lamina and a connective tissue wall with fine trabecualae across the perilymphatic space between this tissue and perosteum of bony labrynth
The receptive areas: Macula utriculi, Macula sacculi, and Cristae ampullares
The cochlea divides the bony cochlea into three cavities. What are these 3 cavities?
Scala vestibuli (upper)
- Contains perilymph
- Continuous with scala tympani at helicotrema
Scala tympani (lower)
- Contains perilymph
- Continuous with scala vestibuli at helicotrema
Cochlear duct (scala media)
- Contains endolymph
- Cecum cupulare: blind end of cochlear duct at apex
What kind of lymph is in the scala media, scala vestibuli, and scale tympani?
Scala media - endolymph
Scale Tympani/vestibuli - perilymph
Responsible for producing endolymph:
Stria vascularis
Endolymph vs perilymph:
Endolymph
- Characteristics of intracellular fluid
- High K+; Low Na+
- Produced by stria vascularis and elsewhere
- Absorbed by endolymphatic duct
Perilymph
- Resembles extracellular fluid
- Source is uncertain
What is the osseous labrynth’s histology?
Bony walls containing the vestibule, semicircular canals, ampullae, cochlea etc
Made of compact bone surroudned by periosteum and simple squamous epithelium
DESCRIBE THE UTRICLE
Upper posterior area where the 3 semicircular canals come together in a wide area
Connected to the saccule
Contains a receptive area called the macula
Describe the saccule:
Joined to utricle
Also connected to cochlear duct
Also has a macula, (a receptive area)
What are the semicicrular ducts?
What are the ampullae?
Where are the receptive areas?
The 3 semicircular canals branch off of the utricle.
There is a superior, lateral and posterior
The swelling on each end right before meeting the utricle is called the ampullae
The receptive areas are located within the ampullae and are called the cristae
So you knwo that maculae and cristae are the receptive areas.
So what cell types are you going to see in these areas?
- Cell types:
- Sustentacular (supporting) cells
- Tall columnar cells
- Between hair cells
- Hair cells
- Type I: globular; kinocilum; long microvilli
- Afferent and efferent innervations
- Type II: cylindrical; kinocilium; long microvilli
- Afferent and efferent innervations
What is the gelatinous mass surrounding the sterocilia nd kinoclila in the maculae and the cristae ampullares?
Cristae ampullares = Cupula
Maculae = Otolithic membrane
Moving the sterocilia in which direction will cause K+ entrance and depolarization?
Stereocilia being bent toward the talllest sterocilia or the kinocilium in the vestibular system
In the vestibular system, looking at the type 1 and type 2 hair cells, what is an easy way to distinguis the two?
Type 1 - innervation looks like a bulb surroundign the bottom fo the hair cell
Type 2 - innervation looks like 1 or 2 little spindly nerves coming off
(This is a Jesse-pinion…)
At what point do the scale vestibuli and scala tympani meet?
This part of the cochlea is best used for detecting what frequency sounds?
They meet at the helicotrema
Detects low frequnecy sounds (Don’t need to knwo this, jsut thought it was cool)
What are the 3 cavity subdivisions of the cochlea?
Scala vestibuli (upper) Contains perilymph
Scala tympani (lower) Contains perilymph
Cochlear duct (scala media) Contains endolymph Cecum cupulare: blind end of cochlear duct at apex
What diviides the scala vestibuli from the scala media?
The vestibular membrane
What structure does the organ of corti sit on top of?
The basilar membrane
What is the limbus spiralis?
Periosteal thickening above the spiral lamina.
(Continuous with basilar membrane)
Describe the cellular parts of the organ of corti
Hair cells (two sets):
Inner hair cells (1 row)
Between inner pillars and inner phalangeal and border cells)
Outer hair cells (3-5 rows)
Between outer pillars and outer phalangeal cells
3 rows: basal coil (high pitches)
4 rows: second coil
5 rows: upper coil (low pitches)
Supporting cells:
Inner and outer pillar cells form an intervening tunnel
Inner and outer phalangeal cells
(also border hensen and caludius - don’t need to know these)
What is actually physcially pushing on the hair cells of the organ of corti?
The tectorial membrane!
Write down the general idea of the cellular amke-up of the organ of corti along with supporting cells.
Check to see the accuracy compared to the picture:
What is physcailly causing cation channels to open when the stereocilia bundles are tilted?
Most likely it is the linking filaments connecting the tops of the sterocilia yanking them open
Where is the spiral ganglion located?
What kinds of cells does it contain?
Spiral ganglion foudn at the jucntion of the osseal spiral lamina and the modiolus
Contains bipolar neurons
Let;s talk innervation:
heres an easy one, what are the main divisions of the 8th cranial nerve?
The vestibulocochlear nerve
Divides into the vestibular nerve and the cochlear nerve
The vestibular nerve then divides into the superior and inferior branches
What is inneravted by the superior branch of the vestibular division of cranial nerve 8?
The horizontal and anterior cristae ampullares
The macula utriculi
part of macula sacculi
What is innervated by the inferior branch of the vestibular nerve?
The posterior crista ampullaris
Most of the macula sacculi
What is innervated by the cochlear (or auditory) nerve?
supplies inner and outer hair cells of the organ of corti
Where are the auditory nerve nuclei found?
The spiral ganglion of the modiolus
