Lecture 17

Question 1

Describe the Auricle

Answer 1

the pinna of the ear and the auditory canal that is composed of integument overlying elastic cartilage

Question 2

Describe the Auditory Meatus (include the composition of the “3rds” of it)

Answer 2

the lining of the ear canal is stratified squamous epithelium with sebaceous glands and ceruminous glands (modified sebaceous glands that earwax)

The outer 3rd of the auditory meatus is composed of elastic cartilage and the inner 2/3rds is composed of bone

Question 3

Describe the Tympanic Membrane (what it separates, external surface, core, and internal surface composition)

Answer 3

a membrane that separates the external auditory canal from the middle ear

The external surface is covered by thin skin

The core is formed of “vascularized, innervated connective tissue”

The internal surface is covered by simple cuboidal epithelium

Question 4

Identify the three auditory ossicles (bones of the ear) and describe their relationship to each
other.

Answer 4

Malleus (hammer): attaches to the tympanic membrane and vibrates as the membrane vibrates

Incus (anvil): intermediate bone between the malleus and stapes

Stapes (stirrup): connects the incus to the oval window
Shaped like a stirrup bc the opening in it makes way for the stapedial artery

Question 5

Name the two openings from the middle ear and relate to the structure of
the inner ear.

Answer 5

Oval window: attached to the stapes on one side and opens up into the scala vestibuli

Round window: a membrane-covered region at the end of the scala tympani

Question 6

List the two muscles (and their insertions) of the middle ear and describe their function.

Answer 6

Tensor tympani: inserts on the malleus

Stapedius: inserts on the stapes

These muscles contract reflexively in response to loud sounds in order to dampen the vibrations of the auditory ossicles

Question 7

List each of the four regions of the inner ear.

Answer 7

Bony labyrinth

Membranous labyrinth

Vestibular organ

Auditory organ

Question 8

Describe the “Bony labyrinth” region of the inner ear (include what it is filled with and what structures it consists of)

Answer 8

complex system of canals and chambers embedded in the pertrous portion of the temporal bone

Filled with high Na+ perilymph

Consists of: semicircular canals, cochlea, scala vestibuli, scala tympani

Question 9

Describe the “Membranous labyrinth” region of the inner ear (include what it is filled with and where it is embedded)

Answer 9

complex system of membranous structures embedded within the chamber of the bony labyrinth

Filled with high K+ endolymph

Question 10

Describe the “vestibular organ” region of the inner ear (include what structures it consists of)

Answer 10

patches of sensory structures that respond to changes in position

Consists of: maculae of the saccule and utricle ; cristae ampullaris of the semicircular canals

Question 11

Describe the “auditory organ” region of the inner ear (include the other name for it)

Answer 11

another name for the cochlea and is a small spiral canal that processes the vibrations that enter the ear, into “sounds” to send to the brain via nerves

Question 12

What are maculae?

Answer 12

they are sensory receptors that are located in the wall of the saccule and utricle

the position of the maculae in the utricle are horizontal while the maculae in the saccule are vertical.

this allows them to detect directional movement of the head

Question 13

Describe the epithelium of the maculae and what they detect

Answer 13

has columnar supporting cells and vestibular hair cells (numerus stereocilia and single kinocilium)

these hair cells on the epithelium are coated by the otolithic membrane, containing otoconia (greek for ear dust)

these otoconia are displaced by endolymph movement to detect linear acceleration of the head (NOT head rotation)

Question 14

Describe the hair cells of the maculae and what they detect

Answer 14

these hair cells on the epithelium are coated by the otolithic membrane, containing otoconia (greek for ear dust)

these otoconia are displaced by endolymph movement to detect linear acceleration of the head (NOT head rotation)

all hair cells are in contact with afferent nerve endings

Question 15

Describe the otolithic memebrane of the maculae

Answer 15

a gelatinous layer containing “calcium carbonate crystals” (ear sand) called otoliths that overlie the epithelium

basically lies between the endolymph (which contains otoliths) and the hair cells that are attached to afferent nerve fibers

Question 16

compare maculae to the cristae ampullares in terms of what they sense and how they sense it.

Answer 16

The maculae and cristae ampullares are both structures that work to sense the position/movement of the head based on movement of endolymph

Maculae use an otolithic membrane, which is attached to hair cells and nerves to detect “linear head movements”

cristae ampullares use a cupula (which is very similar to the otolithic membrane, but lacks ototliths) to detect “angular head movement”

Question 17

What does the cochlear duct (scala media) divide the bony cochlea into?

Answer 17

the cochlear duct divides the bony cochlea into the scala vestibuli and the scala tympani

Question 18

describe the boundaries of the cochlear duct (it doesnt have a medial boundary)

Answer 18

the scala vestibuli lies superior

the scala tympani lies inferior

the stria vascularis lies lateral to the duct

Question 19

what forms the roof and the floor of the cochlear duct?

Answer 19

Vestibular membrane forms the roof of this duct

Basilar membrane forms the floor of this duct

Question 20

Where is the organ of corti located?

Answer 20

it lies on the basilar membrane

Question 21

What is one of the main functions of the stria vascularis?

Answer 21

participates in the formation of the endolymph (K+ rich)