Development of ear

Question 1

Ear

Answer 1

organ of hearing and balance

internal, middle and external ear

Question 2

Internal ear

Answer 2

develops in week 4

thickening of surface ectoderm - otic placode -> cochlear and vestibular ganglia -> otic vesicle

Question 3

Otic vesicle

Answer 3

membranous labyrinth, utricular and saccular
Utricular division -> utricle, semicircular ducts, endolymphatic duct, vestibular apparatus
Saccular division -> saccule, cochlear apparatus

Question 4

Utricle

Answer 4

contains sensory hair cells and otoliths of macula utriculi

responds to linaer acceleration and gravity

Question 5

Semicircular ducts

Answer 5

during 6th week from utricular part
contain sensory hair cells of cristae ampullares
respond to angular acceleration

Question 6

Endolymphatic duct and sac

Answer 6

membranous canal connecting with saccule and utricle and terminating in blind dilation
absorbs endolymph

Question 7

Saccule

Answer 7

contains sensory hair cells and otoliths of macula sacculi

responds to linear acceleration and gravity

Question 8

Cochlear duct

Answer 8

from otic vesicle
mesenchyme surrounding it -> cartilage
contains spiral organ of Corti and endolymph
-Vestibular membrane
-Basilar membrane (from mesoderm)
-Spiral ligament and stria vascularis

Question 9

Spiral organ of Corti

Answer 9

organ of hearing
contains sensory hair cells (stimulated by tectorial membrane)
innervated by spiral ganglion of cochlear nerve

Question 10

Bony labyrinth

Answer 10

consist of vestibule, semicircular canals and cochlea
Membranous labyrinth - mesoderm becomes cartilaginous and ossifies
Mesodermal cells closest degenerate -> perilymphatic space

Question 11

Cochlear and vestibular ganglia

Answer 11

cochlear in models of bony labyrinth

vestibular in base of internal auditory meatus

Question 12

Middle ear

Answer 12

from tubotympanic recess, primitive tympanic cavity
sensory innervation: glossopharyngeal
epithelium from endoderm
tympanic cavity from 1st pharyngeal pouch

Question 13

Malleus

Answer 13

from cartilage of pharyngeal arch 1
attached to tympanic membrane
moved by tensor tympani (mandibular n.)
embedded in mesenchyme until eight month

Question 14

Incus

Answer 14

from cartilage of pharyngeal arch 1
articulates with malleus and stapes
embedded in mesenchyme until 8th month

Question 15

Stapes

Answer 15

from cartilage of pharyngeal arch 2
moved by stapedius m (facial n.)
attached to oval window
embedded in mesenchyme until 8th month

Question 16

Tympanic membrane

Answer 16

separates middle from external ear
from ectoderm from 1st pharyngeal groove
mesoderm
endoderm from 1st pharyngeal pouch

Question 17

Auditory tube

Answer 17

connects tympanic cavity to nasopharynx

from tubotympanic recess - medial part of 1st pharyngeal pouch

Question 18

External auditory meatus

Answer 18

from pharyngeal cleft 1
ectodermal cells forming temporary metal plug
innervated by trigeminal, glossopharyngeal
sebaceous and ceruminous glands in skin

Question 19

Auricle

Answer 19

from six auricular hillocks that surround pharyngeal groove 1
innervated by mandibular, facial, glossopharyngeal, vagus and c2-c3

Question 20

Congenital malformations of the ear

Answer 20

Congenital deafness
Malformation of auricles in chromosomal syndromes
Atresia of external auditory meatus
Congenital cholesteatoma