Histology of the Ear

Question 1

What are the three general ear components?

Answer 1

external ere, middle ear, inner ear

Question 2

What are the two functions of the ear?

Answer 2

hearing and balance

Question 3

What are the components of the external ear? What is it made of?

Answer 3

the auricle (helix, antihelix, tragus, antitragus)

elastic cartilage core, except for lobule which is mostly connective tissue

Question 4

What is the support for the external dutiory meatus?

Answer 4

elastic cartilage for outer 1/3 and temporal bone for the inner 2/3

Question 5

What two glands work together to form cerumen (ear wax)?

Answer 5

sebaceous and ceuminous glands

Question 6

What separates the external and middle ear?

Answer 6

the tympanic membrane

Question 7

FOr the tympanic membrane…

what is the outer surface made of? The core? the inner surface?

Answer 7

outer surface = thin sin

core = two layer sof fibro-elastic connective tissue

inner surface = simple squamous epithelium

Question 8

What structures make up the middle ear?

Answer 8

the tympanic cavity with the ossicles (malleus, incus, stapes)

auditory (eustachian) tube

Question 9

How does the histology of the auditory tube change as it goes from bony portion to pharyngeal opening?

Answer 9

bony: low columnar epithelium with cilia
carilaginous: pseudostratified epithelium with some goblet cells near pharyngeal opening

Question 10

What sort of epithelium covers the ossicles?

Answer 10

simple squamous epithelium

Question 11

What are the two muscles of the middle ear?

Answer 11

stapedius and tensor tympani

Question 12

If the malleus communicates with the tympanic membrane, what does the stapes communicate with?

Answer 12

the membrane over the oval window

Question 13

What are the two “sections” of the inner ear?

Answer 13

the bony labyrinth and then the membranous labyrinth suspended in the bony

Question 14

Starting from the oval window, what are the portions of the osseous labyrinth?

Answer 14

oval window opens into the vestibule

semicircular canals

ampullae of each canal

cochlea with modiolus and spiral lamina

vestibular aqueduct

Question 15

What are the two openings of the vestibule?

Answer 15

oval window (with base plate of stapes)

round window

Question 16

HOw many semicircular canals are there?

Answer 16

6 - three on each side

superior, posterior, lateral

Question 17

What are the ampullae?

Answer 17

they are dilations at the ends of each semicircular canal

Question 18

THe cochlea is a spirally coiled tube like a snail shell in the shape of a cone - what is the bony axial stem called?

Answer 18

the modiolus

Question 19

WHat is the bony, shelf-like projection which spirals around the modiolus liek threads on a screw?

Answer 19

the spiral lamina

Question 20

What kind of bone is the oseeous labryinth carved out of?

Answer 20

compact bone - covered by periosteum and then simple squamous epithelium

Question 21

What fluid fills the osseous labyrinth?

Answer 21

perilymph

Question 22

What are the two chambers of the vestibule?

Answer 22

the utricle (upper posterior location)

and the saccule *(ower anterior position - smaller)

Question 23

Of the utricle and the saccule, which communicates with the semicircular canals and which communicates with the cochlea?

Answer 23

the utricle communicates with the canals and the saccule communicates with the cochlea

Question 24

What is the receptive area in the utricle called? The saccule

Answer 24

they are both macula

so the macula utriculi and macula succuli

Question 25

What is the receptive area of the ampulas?

Answer 25

the cristae ampularis - one for each ampulae

Question 26

What joins the utricle and saccule together?

Answer 26

the y-shaped tube containing the endolyphatic, utricular and saccular ducts

Question 27

What do the non-receptive areas of the inner ear look like histologically?

Answer 27

simple squamous epithelium with a basal lamina

Question 28

What are the two general cell types found in the receptive areas of the inner ear?

Answer 28

the sustentacular cells (supporting cells) Hair cells (the sensory neuroepitheliual cells)

Question 29

What are the two types of hair cells?

Answer 29

type 1 and type 2

Question 30

In what ways are the two hair cell types similar?

Answer 30

they both have 30-100 long microvilli, arranged by length all have one kinocilium (but lose it in the auditory system) have both afferent and efferent innervation in some way or another

Question 31

How do the type 1 and type 2 hair cells differ?

Answer 31

shape: type 1 are more globular, type 2 more cylindrical type 1 hair cells are always located at the border of a cell type 1 cells have more afferents (since they're the main sensory cells) while type 2 cells have more efferents (since they're more the contractile cells of the system) type 1 cells receive their afferents as a sort of cup while the efferents contact the afferent nerve endings instead of the cell itself type 2 cells receive their afferents and efferents directly on the cell surface

Question 32

What is the gelatinous membrane of the maculae called?

Answer 32

the otolithic membrane

Question 33

What is the relationship between the sterocilia of the hair cells and te otolithic membrane?

Answer 33

the cilia are embedded in it

Question 34

What are otoconia?

Answer 34

they are crystals of calcium carbonate and protein embedded on the surface of the otolithic membrane

Question 35

What is the gelatinous membrane of the cristae ampullae (the cristae equivalent of the otolithic membrane)?

Answer 35

the cupula more of a cone shaped area - cilia still embedded init

Question 36

What two membranes subdivide the bony cochlea into three cavities?

Answer 36

Basilar membrane (also supports organ of corti) vestibular membrane

Question 37

What are the three cavities of the cochlea?

Answer 37

scala vestibuli - upper scala tympani - lower cochlear duct (or scala media)

Question 38

Which cavities have perilymph and which has endolymph?

Answer 38

the vestibuli and tympani have perilymph the cochlear duct has endolymph

Question 39

At what point are the scala vestibuli and scala tympani continuous with each other?

Answer 39

the helicotrema

Question 40

What is the cecum cupulare?

Answer 40

it's the blind end of the cochlear duct at the apex of the cochlea - it's not open so endolymph can't leave at that point

Question 41

Where is the helicotrema located?

Answer 41

at the apex of the cochlea

Question 42

What is the limbus spiralis?

Answer 42

it is an area of thickening periosteum just aboe the spiral lamina it bulges into the cochlear dict the lower part is continuous with the basilar membrane

Question 43

What are the main supporting cells of the organ of corti?

Answer 43

the inner and oute rpilar cells form an intervening tunnel while the inner and outer phalangeal cells surround the support the hair cells

Question 44

Describe the two sets of hair cells in the organ of corti?

Answer 44

the inner hair cells are type 1 cells - only 1 row the outer hair cells are type 2 cells = the number of rows bary depending on wher eyou are in the organ of corti

Question 45

How many rows of outer hair cells are there in the different regions of the cochlea/

Answer 45

basal coil = 3 rows (high pitches) second coil = 4 rows upper coil = 5 rows (low pitches)

Question 46

How is the manner in which the phalangeal cells surround the type 1 and type 2 hair cells different? Why is this significant?

Answer 46

The type 1 cels are wrapped tightly intot he inner phalangeal cells the type 2 cells are wrapped losely in between the outer phalangeal cells, so there is a space this is significant because the type 2 cells have contractile capabilities and the space allows them to do so

Question 47

What is the ribbon of relationous material that rests upon the hair cells in the organ of corti?

Answer 47

the tectorial membrane

Question 48

What ganglion is located at the junction of the osseous spiral lamina and modiolus?

Answer 48

the spiral ganglion

Question 49

What types of neuron cell bodies are contained in the spiral ganglion?

Answer 49

bipolar neurons (with myelinated central processes and unmyelinated "dendrites" reaching to the hair cells in the organ of corti)

Question 50

How is the composition of endolymph and perilymph different?

Answer 50

endolymph: high K+ and low Na+ (like intracellular fluid) lerilymph: looks like extracellular fluid

Question 51

What produces the endolymph?

Answer 51

the stria vascularis probably (on the lateral wall of the cochlear duct)

Question 52

What absorbs the endolymph?

Answer 52

the endolymphatic duct

Question 53

In what ganglion are the cell bodies of the vestibular nerve afferents?

Answer 53

the vestibular ganglion in the internal auditory meatus of the temporal bone

Question 54

THe vestibular nerve divides into a seuprior branch and an inferior branch - what do they supply?

Answer 54

superior = horixontal crita ampularis, superior crita ampullaris, macula utriculi, and msall part of th emacula sacculi inferior: posteiro rcrita ampullaris and major portion of the macula sacculi