Ear development

Question 1

بسم الله الرحمن الرحيم
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Inner ear:
Membranous labryinth develops from …….
early in the …..week , athickeninig of the surface ectoderm “…..” appears on each side of the caudal part of………….
The …..invaginates and form …………
in the …..w.eek the ……(……) splits off from the surface of ectoderm
The …… divides into a ventral component called…..and dorsal one called ………

Answer 1

Otic Vesicle
4th week
Otic placode
hindbrain
Otic placode - otic pits
4th week otic vesicle ( otocytes)
otic vesicle dividned into ventral saccule and dorsal utricle

Question 2

Inner ear develops from ….

Answer 2

myeloencephalon of hindbrain

Question 3

The cochlear duct develops in ….week
as ……..from the lower pole of …….
It penetrates the surrounding ,,,,,, and forms 2 1/2 spirals .
its connections with the saccule is then confined to narrow pathway called,,,,,
the surrounding mesecnchyme becomes cartilage two perilmphatic spaces
………..+……… around choclear duct

Answer 3

6th week
tubular outpocket from lower pole of Otic vesicle
Mesenchyme
ductus reunins
scala vestibuli +scala tympani

Question 4

Cochlear duct separated from scala vestibuli by …….
and from scala tympani by…..?
The lateral wall of choclear duct attaced to the cartilage by …….
The median angle connected to ….which will be the future …. of choclea
The epithelial lining the cochlear duct form inner and outre hair cells covered by ….. ?

Answer 4

Vestibular membrane
Basilar membrane
Spiral ligament
Modiluous the future angle of choclea
Tectorial membrane

Question 5

Semicircular canal appears during …..week
developed from …..

Answer 5

6th week
utricle 3 flattened outpockets

Question 6

How smicircular canals formed
?

Answer 6

During 6th week from the flattened 3 outpockets of utricle
2 walls of central potrions of each one are apposed disappaering forming the canals
superior
Posterio
Lateral semiciruclar canals

Question 7

The ends of semiciulara canals forms ….. forming,,,,,,,,,,, mention its importance

Answer 7

Ampulla
Critsa amupillaris
sensory cells for equilibrium maintanance

Question 8

Menetion innervation of inner ear

Answer 8

Vestibulo-cochlear ganglion formed by?
During formation of otic vescile a small group of cells breaks awary from the ganglion
May due to neural crest cells migration

Question 9

Vestibulochoclear ganglion supplies ?

Answer 9

Sensory cells of Organ of Corti
Saccule Utricle and its semiciruclar canals

Question 10

Middle ear development

Answer 10

The lining epithelium from the Endodermal tubotympanic membeane = 1st pharyngeal arch
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Osciles from the cartilage of 1st pharyngeal arch ( malleus - incus ) + 2nd pahryngeal arch (stapes)
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Muscles : Tensor tympani 1st arch = Manidbular supply
Stapedius 2nd arch = Facial nerve supply

Question 11

During fetal life the tympanic cavity expands ……. by …… of the surrounding tissue forming ……. .
After birth the bone of the developing mastoid process is also ,,,,,,,
Later most of the mastoid air sacs come in contact with ,,,, + ,,,,,,,,

Answer 11

Dorsally - Vacuolation - mastoid antrum
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Pnematiezed - antrum -Tympanic membrane

Question 12

External auditory meatus develops from ,,,,, pharyngeal arch ?
in the …. month the epitlial cells at its bottom proliferate forming a solid metal plug that dissoslves at ….. month if it ipersists = congenital dafness

Answer 12

First
3rd - 7th

Question 13

Ear drum
tympanic membrane formed of ?

Answer 13

Ectodermal epithleial lining
Mesenchymal intermediate layer
Endodermal from first pharyngeal arch

Question 14

The Six mesenchymal hillocks surrounding first pharyngeal arch fuse to form ?

Answer 14

Auricle

Question 15

What it the initial site of external ear ?

Answer 15

Lower neck but with progression in development it ascends to its normal postion to sides of head at level of eye

Question 16

Congenital deafness write shortly about

Answer 16

Associated with Deaf-mutism
due to :
1-Malformation of membranous or bony labyrinths
2-Malformation of Osciles + eardrum
3-absence of tympanic caivty or External auditory meatus
It is belieced to be hereditary but now we know it is asscoicated with : ERcP THD
Erythroblastosis fetalis
Rubella
Poliomyelities
Toxoplasmosis
Hyperthyroidism
Diabetes

Question 17

Variation of auricle clinical imp mention

Answer 17

May be associated with
1-Kideny malfomatin
2-chormosme determined syndromes
3-First arch syndrome

Question 18

Describe first and second order neurons of auditory pathway

Answer 18

1ST:
Cetnral process of bipolar cells From spiral ganglion in inner ear to internal acoustic meatus to pons
2nd :
From pons branching into 2 divisions one to dorsal and the other to ventral Choclear nuclei
theri axons forms trapezoid body then relay in Superior olivary nusclei+ Trapezoid nucleus of the same or opposite side

Question 19

Describe 3rd and 4th order neurons of auditory path

Answer 19

3rd :Axons of superior olivary nucleus + trapezoid nuscleus ascneds in the lateral leminscus then to Nucelus of lateral leminscus sone relay and some contiunes then to Inferior colliculs some relay and some contiunues then to MGB
4th :
MGB gives audiotry raidation passing in the sublentifrom nucleus of Internal capsule then to area 41 primary auditory one

Question 20

الحمدلله رب العالمين