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Acoustics III: Inner Ear > Membranous Cochlea & Related Structures > Flashcards

Membranous Cochlea & Related Structures Flashcards

1
Q

Where is the membranous cochlea located?

A

Follows the spiral shape of the bony cochlea from base to apex.

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2
Q

What are the three scalae within the membranous cochlea?

A

Scala vestibuli (superior), scala media, and scala tympani (inferior)

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3
Q

What membranes separate the scalae?

A

The Basilar membrane & Reissner’s membrane

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4
Q

What is the Basilar membrane? What are it’s properties?

A

Membrane connected to the spiral ligament on the outer wall of the bony cochlea and to the osseus spiral lamina. Stiffer at base, flaccid at apex, and narrow at base, wider at apex.

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5
Q

What is Reissner’s membrane?

A

Forms the roof of the cochlear duct (scala media) and the floor of the scala vestibuli.

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6
Q

What are the two membranous communication ducts?

A

The Ductus Reuniens, and the Endolymphatic duct.

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7
Q

What is the Ductus Reuniens?

A

A membranous duct that communicates from the basal region of the cochlea with the saccule of the vestibule.

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8
Q

What is the Endolymphatic duct?

A

The membranous duct housed within the osseous vestibular aqueduct that contains endolymph. Helps to regulate endolymphatic pressure. Courses from the vestibule to the endolymphatic sac, on the posterior surface of the temporal bone.

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9
Q

What are the three cochlear fluids?

A

Perilymph, endolymph, and cortilymph.

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10
Q

What is perilymph? What spaces does it fill?

A

Similar to cerebrospinal fluid in ionic composition- high in Sodium and low in Potassium. Fills the Scala Vestibuli, Scala Tympani, and the perilymphatic space between the osseous portion and membranous portion of the vestibule and semicircular canals.

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11
Q

What is endolymph? What spaces does it fill?

A

Similar in ionic composition to intracellular fluid- high in Potassium, low in Sodium. Fills the scala media (cochlear duc) and membranous portion of the vestibular system (utricle, saccule, & SSC).

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12
Q

What is cortilymph? What spaces does it fill?

A

Similar in ionic composition to cerebrospinal fluid (similar to perilymph)- high in Sodium, low in Potassium. Fills between the pillar cells (within tunnel of Corti) and around the base of hair cells in the cochlea.

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13
Q

What is the Scala Media? (AKA Cochlear duct)

A

Houses the sensory organ for hearing: the Organ of Corti.

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14
Q

What is the Organ of Corti? What does it consist of?

A

Lies on top of the basilar membrane and runs the length of the cochlear duct. Consists of supporting structures, sensory cells and nerve fibers.

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15
Q

What is the Tectorial membrane? What does it attach to? What are it’s properties?

A

Situated immediately above the organ of Corti and covers it’s entire length. Attached to the spiral limbus on one side and attached to supporting cells on the other. The mass and dimensions of the membrane increase from base to apex, with stereocilia tips of outer hair cells firmly embedded in the underside of the membrane.

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16
Q

What is the Reticular lamina? What does it separate? What is it formed by?

A

Forms the ceiling of the sensory and supporting cells of the organ of Corti. Separates the endolymph from the internal structures of the organ of Corti. Formed by the phalanges of the Deiter’s and inner phalangeal cells, as well as inner and outer pillar cells, along with top margin of the sensory cells (cuticular plate).

17
Q

What are the cilia/hair cells that penetrate the Reticular lamina bathed in?

A

Only the cilia of the hair cells are bathed in endolymph. Otherwise, the reticular lamina forms a barrier to the endolymph compartment and separates the hair cells from it. The hair cells proper are bathed in cortilymph.

18
Q

What are the two structures located in the lateral wall of the cochlear duct?

A

The spiral ligament and the striavascularis.

19
Q

What is the spiral ligament?

A

Characterizes lateral wall of the cochlea by a thickening of the periosteum, which projects inward to form the BASILAR CREST.

20
Q

What is the striavascularis? What does it supply?

A

Located in lateral wall of cochlear duct. Supplies blood & nutrients to the cochlea and may manufacture endolymph.

21
Q

What are the Inner Hair Cells (IHC)? What shape are they? How many mitochondria do they have?

A

IHC form a single row on Basilar membrane with 3500 cells. Take a oval/flask like shape and contain more mitochondria than the Outer Hair Cells.

22
Q

Describe the stereocilia of the IHC

A

Arranged in three rows in a U-shape pattern on top of the hair cell/on top of the cuticular plate, and are NOT embedded in the tectorial membrane.

23
Q

What are the Outer Hair Cells (OHC)? What shape are they? What do they contain?

A

Three to five rows on Basilar membrane (12,000). Are cylinder in shape and contain contractile proteins to allow for expansion and contraction of the hair cells-therefore, they have a motor AND sensory response to stimulation.

24
Q

What are contractile proteins?

A

Actin, myosin, prestin…

25
Q

Describe the stereocilia of the OHC…

A

Located on top of the cuticular plate that anchors them and are attached to the underside of the tectorial membrane. Each cell has three rows of stereocilia that form a W-shape on each OHC.

26
Q

What is Kinocilium?

A

The tallest of the stereocilia for each hair cell (though not always present in the cochlea).

27
Q

Describe the pores of stereocilia…

A

Pores that open upon excitation (depolarization) allowing Potassium (K+) ions into the cell.

28
Q

What are cross-links?

A

Fibers that connect cilia together in order for them to move as a unit.

29
Q

What are tip-link structures?

A

Small filaments that connect to other cilia and ion channels. Connect to mechanotransduction channels and open these channels when cilia are deflected.

30
Q

What are the two supporting cells that we discuss in this class?

A

Deiter’s cells and Inner & Outer Pillar cells.

31
Q

What are the three main parts of Deiter’s cells? What purpose do Deiter’s cells serve?

A

The three main parts are the cell body, stalk, and phalangeal process. Purpose is to support the hair cells, with phalanges helping to form the reticular lamina.

32
Q

What are the Inner and Outer Pillar cells?

A

Form the tunnel of Corti and contribute to the reticular lamina. Located between the IHCs and OHCs in order to maintain a strong structural attachment between the reticular lamina and basilar membrane.

33
Q

What are the three divisions of the membranous labryinth?

A 
Semicircular canals (Vestibular system, for hearing/balance)
Utricle & Saccule (Vestibular system)
Cochlear duct (Scala media/System for hearing)

Acoustics III: Inner Ear (9 decks)

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