15. Ear Development

Question 1

external ear

Answer 1

aricle, external acoustic meatus, external layer of TM

Question 2

middle ear

Answer 2

three ossicles, internal layer of TM, middle ear cavity

Question 3

internal ear

Answer 3

vestibulocochlear organ

Question 4

innervation of the ear

Answer 4

• great auricular n.
• CN V3: auriculotemporal
• CN VII
• CN X: auricular branches

Question 5

caused by abnormal migration of NCC

Answer 5

• skin tags
• anotio (no ear)
• microtia (small ear)

Question 6

external auditory meatus

Answer 6

first pharygeal cleft 1 or pharyngeal groove 1

Question 7

meatal plug

Answer 7

ectodermal cells that fill the meatus (disappear before birth)

Question 8

innervation of meatus

Answer 8

CN V3 and CN IX

Question 9

inner ear derived from what embryonic layer

Answer 9

ectoderm

Question 10

components of the membranous labyrinth

Answer 10

• utricle (dorsal)
  
  • endolymphatic duct and sac
  • semicircular ducts and ampullae (lateral canal)
  • macula of utricle
• saccule (ventral)
  
  • cochlear duct
  • ductus reunions
  • macula of saccule, organ of Corti

Question 11

function of ampullae

Answer 11

acceleteration

Question 12

function of macula

Answer 12

gravity

Question 13

function of Ogan of Corti

Answer 13

sound vibration

Question 14

innervation of CN VIII

Answer 14

vestibular ganglion and spiral ganglion

Question 15

produced by the stria vascularis

similar in content to the intracellular fluid

Answer 15

endolymph

*stored in endolymphatic sac

Question 16

free passage from subarachnoid spacei nto the inner ear

similar in content to CSF

Answer 16

perilymph

*may come from filtration of blood in perilymphatic space

Question 17

embryonic layer of membranous labyrinth

Answer 17

mesenchyme/NCC

Question 18

Where is periplymph located?

Answer 18

• scala vestibuli
• scala tympani

Question 19

Where is endolymph located?

Answer 19

scala media

Question 20

Where is stria vascularis located?

Answer 20

within the ligaments that stabilize the organ of Corti

Question 21

external auditory meatus

Answer 21

1st pharyngeal cleft / ectoderm

Question 22

tubotympanic recess

Answer 22

1st pharyngeal pouch / endoderm

Question 23

tympanic membrane

Answer 23

ectoderm, mesoderm, and endoderm

Question 24

malleus and incus

Answer 24

pharyngeal arch 1 (NCC)

Question 25

stapes

Answer 25

pharyngeal arch 2 (NCC)

Question 26

covering of ossicles

Answer 26

endodermal epithelium

Question 27

inserts into handle of malleus

prevents damage from loud sounds

1st pharyngeal arch mesoderm

Answer 27

tensor tympani m.

Question 28

inserts on neck of stapes

pulls stapes posteriorly and tilts its base in the oval window

action prevents damage from loud sounds

from 2nd pharyngeal arch mesoderm

Answer 28

stapedius m.

Question 29

causes of congenital deafness

Answer 29

• genetic factors*
• neurosensory structures of inner ear
• infections

Question 30

ear symptoms of congenital infections: CMV

Answer 30

senorineural hearing loss

Question 31

ear symptoms of congenital infections: Rubella virus

Answer 31

sensorineural deafness

Question 32

ear symptoms of congenital infections: Toxoplasma gondii

Answer 32

hearing loss

Question 33

ear symptoms of congenital infections: Treponema pallidum

Answer 33

congenital deafness