Ear

Question 1

What are the functions of the ear?

Answer 1

1. Auditory stimuli
2. Auditory to mechanical & nervous stimuli
3. Transmit nerve impulse to CNS via CN VIII (vestibulocochlear nerve)

Question 2

What are the 3 parts of the ear?

Answer 2

hearing & balance
1. External = auricle/pinna & external auditory meatus
2. Middle = tympanic cavity, tympanic membrane (ear drum), 3 ossicles connected to pharynx through eustachian tube
3. Inner = membranous labyrinth enclosed in temporal bone

Question 3

Describe the external acoustical meatus.

Answer 3

-annular (black arrow) & auricular cartilage (arrow head) = cartilaginous portion of external acoustic meatus
-dense, white, fibrous CT attached the annular cartilage to osseous rim of external acoustic meatus (asterisks)
-incudostapedius joint (white arrow)

Question 4

Describe ceruminous glands.

Answer 4

-apocrine
-secrete cerumen (ears wax)

Question 5

Describe the tympanic cavity.

Answer 5

-tympanic membrane (arrows) extends toward tympanic cavity (T)
-external acoustic meatus (M)
-calvaria = brainstem (B)
-manubrium of malleus (arrowhead)

Question 6

Describe the tympanic membrane in the horse VS dog.

Answer 6

HORSE: (A)
-tympanum = round
-manubrium of malleus = central

DOG: (B)
-tympanum = oval/comma shaped
-manubrium of malleus = C shaped

Question 7

Tympanic membrane (picture).

Answer 7

Question 8

Describe the guttural pouch in the horse.

Answer 8

-ventral expansion of auditory tube in horse

Question 9

Describe the auditory ossicles.

Answer 9

facial & vestibulocochlear nerve enter ear through internal acoustic meatus
-ossicles connect tympanic membrane to vestibular window of inner ear

Question 10

Describe the organs of equilibrium & motion detection.

Answer 10

vestibular apparatus of inner ear
-utricle (H)
-saccule (V)
-semicircular ducts (3)
[all contain neuroepithelial cells:
~macula utriculi
~macula sacculi
~crista ampullaris = angular acceleration/deceleration]

Question 11

Describe the cochlea.

Answer 11

“Organ of corti” = hearing
-3 chambers
>middle chamber = cochlear duct - spiral organ with hair cells - sense vibrations (sounds)

Question 12

Describe the structure of the cochlea.

Answer 12

-Scala vestibuli & scala tympani = perilymph & are the bony labyrinth of cochlea
-cochlear duct = membranous labyrinth of cochlea derived from optic vesicle filled with endolymph

Dashed red rectangle = spiral organ - hair cells (H&E)

Question 13

Organ of corti (picture).

Answer 13

Question 14

Describe otoliths.

Answer 14

-located within gelatinous membrane & their movement bends stereocilia of neurosensory hair cells
-detect static equilibrium & linear acceleration
-uterine & saccule are maculae that run perpendicular

Question 15

Describe the semicircular ducts.

Answer 15

-ampullae that contain crista ampullaris
-cupula = gelatinous & movement detected by stereocilia of neurosensory hair cells
-detects rotational movement

Question 16

Saccule & crista ampullaris (vestibular apparatus).

20.12 - macula of saccule 20.13 - crista ampullaris

Answer 16

Question 17

Describe the endolymph.

Answer 17

-fluid in membranous labyrinth of inner ear
-high in K
-bathes inner ear cell & allows to function normally

Question 18

Describe the endolympatic system in amphibians & reptiles.

Answer 18

-large diverticula (sac)
>control pressure, fluid & ion homeostasis (esp Ca)
>located behind eyes
-neuroectoderm (sensory)

Question 19

Describe the lateral line system.

Answer 19

-in fish: larval & adult
-tactile sense organ
-detect movement & change in pressure

Question 20

Describe Jacobson’s organ.

Answer 20

-tongue extension & retraction in reptile
-vomeronasal organs
-chemoreception

Question 21

Compare the vomeronasal organ in the mouse.

Answer 21