Anatomy and Cell Biology 3309 Lecture Notes - Lecture 31: Membranous Labyrinth, Cochlear Duct, Basilar Membrane
2 May 2018
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The Ear 2 - The vestibular system
- Vestibular system makes us aware of movements
Anatomy of the Ear
- Inner ear is the space within the bone
o It is embedded in the bone!
o Perilymph filled space –extracellular fluid
The Inner Ear
o Membranous labyrinth formed by membranes that is suspended within the inner ear, the
opening within the bone (osseous labyrinth)
▪ Within the osseous labyrinth (canal and opening where the cochlea) – space within
the bone is filled with perilymph. Within the perilymph filled space, the
membranous labyrinth is suspended (floats in there)
- Membranous labyrinth is a continuous system filled with endolymph (fluid that is salty but more
intracellular fluid, high in potassium – important for physiology)
o It contains one portion of the cochlea (endolymph filled space in the cochlea) = Scala media
▪ Scala media or the cochlear duct
▪ Organ of Corti sitting on the basilar membrane of the Scala media
▪ Scala media is delimited by basilar membrane and the Reissner’s membrane
- Scala media is connected to these two big structure = utricle and saccule
o They are two big space that give rise to semicircular ducts
▪ These ducts are round that sit to one another in a rectangular angle (like a box)
▪ Entire structure is filled with endolymph and is continuous
- There are nervous structure – there is innervation to different parts of the inner ear
o There is innervation to the organ of Corti sitting on the basilar membrane along the Scala
media
▪ This is where the hair cells are, which are innervated by the spiral ganglion cells that
pick up the signals from the hair cells and to the acoustic nerve
▪ Organ of Corti is our sensory organ in the Scala media
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o There are two sensory structures, one in the saccule and one in the utricle
▪ They are innervated by the same nerve (8th nerve) – but the vestibular nerve
▪ The utricle and saccule are at a 90-degree angle to one another. One is horizontal,
the other is vertical
o Semi circular ducts within the semicircular canals
▪ They have thickenings = Ampulla there are sensory organs. In each Ampulla we
have hair cells (also in the utricle and saccule), innervated by the vestibular nerve
- NOTE: THE AUDITORY NERVE AND VESTIBUALR NERVE = 8TH NERVE
o Vestibular branch innervates sensory organs in saccule and utricle
▪
- INNERVATION TO
o ORGAN OF CORTI
▪ Innervated by auditory nerve
o STRUCTURES IN UTRICLE AND SACCULE = Macula utricle, macula sacculi
▪ Innervated by vestibular nerve
o ONE IN EACH OF THE 3 AMPULA (one on each semicircular canal)
▪ Innervated by the vestibular nerve
The membranous labyrinth
- Note: the inner nerve is often depicted with an outer structure but it does not exist
o The inner ear is just the opening within the bone that is filled with perilymph
o Suspended within the bony structure is the membranous labyrinth that is continuous with
the utricle, saccule, scala media and 3 semicircular ducts
- Image on bottom:
o Purple = membranous labyrinth
▪ ENDOLYMPH
o Blue = osseous labyrinth
▪ Opening in the space within the bone, filled with perilymph
▪ PERILYMPH
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The Cochlea
- Scala vestibule and scala tympani
o Perilymph filled spaces
o Surround the endolymph filled space – scala media is the part of the membranous labyrinth
that is continuous with the utricle, saccule and the semicircular duct (all filled with
endolymph)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Vestibular system makes us aware of movements. Inner ear is the space within the bone. It is embedded in the bone: perilymph filled space extracellular fluid. Within the perilymph filled space, the membranous labyrinth is suspended (floats in there) Membranous labyrinth is a continuous system filled with endolymph (fluid that is salty but more intracellular fluid, high in potassium important for physiology) It contains one portion of the cochlea (endolymph filled space in the cochlea) = scala media. Scala media or the cochlear duct: organ of corti sitting on the basilar membrane of the scala media. Scala media is delimited by basilar membrane and the reissner"s membrane. One is horizontal, the other is vertical: semi circular ducts within the semicircular canals, they have thickenings = ampulla there are sensory organs. In each ampulla we have hair cells (also in the utricle and saccule), innervated by the vestibular nerve.
