Inner ear anatomy Zak Flashcards
(25 cards)
Describe the vestibular system
Sensory system to provide infomation about head movement, position, balance and orientiation in space.
Where is the vestibular system located?
Inner ear
The inner ear is composed of
Cochlea
Semicircular canals -3 fluid filled canals
Vestibulocochlear nerve 8
What do Otolith organs sense?
Sense linear acceleration and head position to gravity
The hair cells are
The sensory cells of the inner ear -Mechanoreceptors
What are the names of the two otolith organs and what do they sense?
Utricle and Saccule- Sense linear acceleration & head position
What is the fluids in the inner ear?
Endolymph- potassium rich
Perilymph- Sodium rich
What are pillars cell?
Another supporting cell type found between inner and outer hair cells
What are deiters cells- location, fucntion, projection
Supporting cells of the inner ear cochlea located in organ of corti.
These cells provide structural support.
Deiters cells also have a projection, the phalangeal process, that extends upward to the reticular lamina, a stiff membrane that covers the organ of Corti.
What is the ampulla and cupula- location & function
Located in semicircular canals, the cupula is a gelatinous structre in ampulla.
Function- detecting head rotation and maintaing balance by transducing fluid movement to nerve signals
How many mechnosensory hair cells in inner ear
15000
Main function of Inner hair cells
Neurosensory transduction-
Mechnotransduction of the vibrations to electrical signal
Main function of Outer hair cells
Motor of mechnical amplifcation of sound siganls
Describe how prestin amplifes sound?
The OHCs amplify through mechanical motor action.It is made of the Prestin motor protein. So when the stereocilia of the hair cells is brushed- leads to Potassium channel activation- The influx of potassium leads to depolarization- activates the prestin. Now the prestin causes contraction of the outer hair cell bodies. Then it repolarizes and the prestin causes relaxation of the OHC bodies. This is a repeated phenomena to generate the energy in order to amplify the sound signal.
what are pillar cells
Pillar cells: another supporting cell type found between inner and outer hair cells
Describe Tonotopy of inner ear?
Each sound frequency is detected along particular region of cochlea basilar membrane. apex- low frequency.
What is the otic placode
The thickining of the ectoderm bilaterally around week 3.
Describe how inner ear forms from development
1.Optic placode thickening occurs
2.Placode begins to invaginate to form optic cup
3.Eventually cup closes to form optic disc and the neuroblast forms now too
4.The neuroblast separate out from the otic epithelium to form the vestibulocochlear neurons
5.The optic vesicles transforms into the inner ear
Describe morphological changes in inner ear?
Size increase - intense proliferation
Ventral body part elongates
Around day 10 the semicircular canals begin to form
Coils begin to form - to form cochlea
Proliferation of cells
Ganglion innervate sensory organs and the hair cells of these organs
Why is paint filling used
They used paint filling technique- injected a white dye to visualise the development and image it. Make walls of the inner ear transparent to be able to visualise it as the inner ear is hollow/empty inside
What gives rise to the development of the inner ear
Regionalized expression of transcription factors
What is hmx2
transcription factor important for forming semi circular canals. Found this using both KO of hmx2 using LacZ
What did she mean by saying developemnt is modular dependent?
Several TFs are distinctly expressed in certain domains to form certain inner ear parts so its modular.
What is the otocyst?
The otocyst is the embryonic precursor of the inner ear,
-derived from the otic placode-thickened ectoderm that forms next to the hindbrain at about E8. 5 and gives rise to all inner ear structures including neuronal, sensory, and nonsensory structures.
