Microanatomy of ear

Question 1

Where are hearing and balance receptors (same receptor type) located in the ear?

Answer 1

• petrous part of temporal bone
• balance more detected at vestibular apparatus
• hearing more at cochlea

Question 2

What epithelium lines the external auditory canal

Answer 2

Stratified squamous which contain hair follicles and sebaceous glands

Question 3

What glands secrete ear wax?

Answer 3

ceruminous glands

Question 4

What is the function fo the pinna?

Answer 4

collects and amplifies sound

Question 5

What is the function of the Eustachian tube?

Answer 5

equilibrates pressure on either side of the eardrum

Question 6

What is the function of the auditory ossicle?

Answer 6

• transmits vibration from tympanic membrane to oval window
• convert sound waves to mechanical vibration in tissue
• amplify the vibrations

Question 7

What are the three ossicles?

Answer 7

Malleus connects to incus which connects to stapes

Question 8

What are the two muscles in the ear which protect from loud sounds?

Answer 8

stapedius and tensor tympani which dampen sound by

work to pull the tympanic membrane and stapes to stop them vibrating

Question 9

What are the two labyrinths which make up the inner ear?

Answer 9

• Bony labyrinth

- Membranous labyrinth

Question 10

What is the fluid that flows through the bony labyrinth called?

Answer 10

perilymph

Question 11

What are the two sensory regions of the inner ear?

Answer 11

Vestibular apparatus (balance, posture & movement)
Cochlea (hearing)

Question 12

What fluid flows through membranous labyrinth

Answer 12

endolymph

Question 13

What is the difference in the compositions of perilymph and endolymph?

Answer 13

Peri - high Na+ and low K+

Endo - low Na+ and high K+

Question 14

What is the function of the different compositions in the two fluids

Answer 14

allows for proper conduction of current

Question 15

What are the two parts of the vestibule?

Answer 15

Utricle

Saccule

Question 16

What is the function of the vestibule?

Answer 16

Use ‘hair cells’ within the Macula (sensory) region of utricle and saccule to detect linear acceleration and perceive direction of gravity

Question 17

Through what cranial nerve will the vestibules send information through?

Answer 17

vestibulocochlear (VIII)

Question 18

What is the function of the semicircular canals?

Answer 18

detect rotational movement of head and body

Question 19

What are the three chambers found in the cochlea and what fluid would you find in each?

Answer 19

Cochlear duct - endolymph
Scala tympani - perilymph
Scala vestibuli - perilymph

Question 20

What structure does the vestibular nerve connect to within the cochlea?

Answer 20

Organ of corti

Question 21

What two membranes separate the chambers in the cochlea?

Answer 21

vestibular (cochlear duct and scala vestibuli)
basilar membrane (cochlear duct and scala tympani)

Question 22

What is the function of organ of Corti?

Answer 22

converts sound vibrations to nerve impulses

Question 23

Describe the structure of the organ of corti?

Answer 23

Made up of

1) tectorial membrane (lies over the top)
2) outer hair cells (connect to tectorial membrane via sterocilia)
3) inner hair cells (connect to tectorial membrane via sterocilia)
3) pharyngeal and pillar cells

Question 24

What is the function of the outer hair cells?

Answer 24

contract when stimulated, pulls on tectorial membrane

Question 25

What is the function of the inner hair cells?

Answer 25

Trigger hearing by cochlear nerve

Question 26

How is a the vibration sent by the stapes transformed into a nerve impulse?

Answer 26

• Stapes acts as piston against the oval window
• creating a pressure wave which moves through the perilymph of scala vestibuli
• pressure wave can pass through the vestibular membrane into cochlear duct
• then through basilar membrane to perilymph of scala tympani
• movement within the endolymph results in displacement of the stereo cilia of the outer hair cells
• outer hair cells contract pulling the tectorial membrane
• tectorial membrane then shakes inner hair cells
• Neurotransmitters within inner hair cells stimulate cochlear nerve

Question 27

Where in the cochlear and high and low frequencies detected?

Answer 27

high frequencies are detected in the apex (travel furthest down cochlea)
Low frequencies are detected at the base (Start of cochlea), narrower and stiffer here which is why responds best to low frequencies

Question 28

Where in the brain do impulses from the cochlear nerve travel to?

Answer 28

auditory cortex