The Ear

Front 1

What are the osseous and membranous labyrinth? What are they filled with?

Back 1

Osseous labyrinth:

-space within petrous bone lined by mesh-like connective tissue

- perilymph (high in Na+ and low in K+ - like intracellular fluid)

Membranous labyrinth:

- surrounded by osseous labyrinth

- contains specialized sensory regions

- endolymph (high in K+ and low in Na+)

Front 2

Where do semicircular canals emerge and end?

Back 2

Vestibule

Front 3

Where does the blood supply to the inner ear come from?

Back 3

Labyrinthine artery, a branch of basilar artery

Front 4

What structure is at one end of each semicircular canal?

Back 4

Ampulla

Front 5

What is the vestibule?

Back 5

Space connected to semicircular canals posteriorly and cochlea anteriorly

Front 6

What structure does the vestibular aqueduct come from?

Back 6

- vestibule

Front 7

What structure inserts onto the oval window?

Back 7

Stapes

Front 8

What is the bony central axis of the cochlea?

Back 8

Modiolus

Front 9

What are osseous spiral lamina?

Back 9

Spiraling shelf off o the modiolus that indents the inner edge of the cochlea

Front 10

Descibe the spiral ganglion

Back 10

Composed of bipolar cells

Fibers of 8th nerve

Front 11

What is the spiral ligament?

Back 11

Outside wall of cochlea, dense connective tissue

Front 12

What are the three tubular compartments of the cochlea? Which labyrinth are they located in?

Back 12

Osseous labyrinth:

Scala vestibuli - connects with oval window

Scala tympani - connects with round window

Membranous labyrinth:

Scala media (middle compartment)

Front 13

What is the connection between the scala vestibuli and scala tympani? WHere is it located?

Back 13

Helicotrema

At apex of cochlea

Front 14

Where is perilymph secreted by?

Back 14

Blood vessels in connective tissue of osseous labyrinth

Front 15

How are endolymph and perilymph prevented from mixing?

Back 15

occluding zonules in cells lining membranous labyrinth

Front 16

Where is the crista ampullaris located? What is its function?

Back 16

In the ampulla of the semicircular canal

Detects rotational movements of head

Front 17

T/F: The semicircular duct is continuous with the utricle

Back 17

True

Front 18

T/F: The utricle is connected to the saccule by a small duct

Back 18

True

Front 19

What travels within the vestibular aqueduct?

Back 19

Endolymphatic duct and sac which is a tube off of the connecting duct between the utricle and saccule

Front 20

What is the function of the utricle and saccule?

Back 20

Detecting linear acceleration.

Front 21

How is the saccule connected to the cochlea?

Back 21

Small duct called Ductus Reuniens

Front 22

What forms the roof and floor of the scala media/cochlear duct?

Back 22

Roof= vestibular membrane (Reissner's)

Floor= basilar membrane (organ of Corti located on this)

Front 23

What forms the tectorial membrane?

Back 23

Spiral limbus - supported by osseous spiral lamina (part of osseous labyrinth)

Front 24

What secretes endolymph?

Back 24

Outer wall of cochlear duct = stria vascularis

Spiral ligament (part of osseous labyrinth) is located beneath stria vascularis

Front 25

Describe the pathway/structure of sensory signals in sensory organs of the inner ear.

Back 25

- Kinocilium (cilium-like structure)/Basal body with sensory cells (stereocilia)

- Longest stereocilia adjacent to kinocilium

- K+ channels in stereocilia open due to adjacent stereocilia

- If cell is depolarized, more neurotransmitter released on 8th nerve processes, increased signal to auditory centers of brain

- Hair cells influenced by axons coming from brain stem (efferent endings)

Front 26

In which direction do stereocilia need to lean to cause depolarization?

Back 26

Toward kinocilium

If away, hyperpolarization occurs

Front 27

T/F: Crista ampullaris runs parallel to semicircular duct axis

Back 27

False: runs perpendicular

Front 28

What are the two types of cells in the crista ampullaris?

Back 28

Supporting cells with secretory granules

Sensory hair cells

Front 29

Where are kinocilia and stereocilia of crista ampullaris embedded?

Back 29

Cupula

Front 30

What does the crsita ampullaris detect?

Back 30

head rotation

Front 31

Describe the sensory maculae of the utricle and saccule.

Back 31

Stereocilia embedded in otolithic membrane

Otoliths present (crystalline inclusions) that increase mass and augment effect of accelerating forces

Front 32

T/F: The hair cells in the organ of corti consist of basal body but no kinocilium

Back 32

True

Front 33

Where are the highest and lowest sound frequencies transduced?

Back 33

Highest= base of cochlea

Lowest= apex of cochlea

Front 34

How many layers of inner and outer hair cells does the ORgan of Corti have?

Back 34

Inner = single row

Outer = 3-5 rows

Separated by inner tunnel (space)

Front 35

T/F: The base of the hair cells rest on the basilar membrane

Back 35

False, rest on phalangeal cell

Front 36

Where are stereocilia of hair cells in organ of corti embedded?

Back 36

tectorial membrane

Front 37

What structures line the inner tunnel?

Back 37

Pillar cells and phalangeal cells

Both contain many microtubules and intermediate filaments

Front 38

What forms the rigid reticular lamina?

Back 38

Pillar and phalangeal cells

Apical portions of hair cells are locked here via zonula adherens and zonula occludens junctions

Front 39

How are receptor potentials in the organ of corti produced in the sensory cells?

Back 39

Sound causes shifting of tectorial membrane and reticular membrane which deviates stereocilia

Neurotransmitters are released due to afferents from spiral ganglion cells (some which traverse inner tunnel)

Front 40

What causes vertigo?

Back 40

Disturbances in vestibular function.

Front 41

What is Menieres disease?

Back 41

Swelling of membranous layer leading to dizziness, tinnitus and low frequency hearing loss

Motion sickness (over stimulation of utricle/saccule)

Front 42

What is the difference between conductive and sensorineural hearing loss?

Back 42

Conductive = break in conduction pathway from atmosphere to ear: tympanic membrane, ankylosis (otosclerosis)

Sensorineural= loss of hair cells of nerve 8 fibers

Presbyacusis is most common type (loss due to age)

Front 43

How does hypothyroidism affect hearing loss?

Back 43

Reduced production of thyroid hormones T4 and T3, iodine deficinecy, leads to hearing loss

Replacement of thyroid hormone alleviates hearing loss

Front 44

What is Pendred syndrome?

Back 44

Causes early heating loss in children

Genetic disorder can also affect thyroid gland

Carrier of mutated SLC26A4 gene

Replacement therapy of thyroid hormone does not reverse hearing loss