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ENT > Embryology of the Pharyngeal Arches and Ear > Flashcards

Embryology of the Pharyngeal Arches and Ear Flashcards

1
Q

what is gastrulation

A

formation of the trilaminar disc- happens in week 3

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2
Q

what happens in gastrulation

A

invagination of the epiblast cells through the primitive streak to form the definitive endoderm and mesoderm

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3
Q

what is the mesoderm organised into

A

paraxial, intermediate and lateral plates

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4
Q

what is the neural crest derived from

A

the ectoderm

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5
Q

what folding happens in the embry

A

lateral and craniocaudal

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6
Q

what does the neural crest form

A

melanocytes, craniofacial cartilage and bone, smooth muscle, peripheral and enteric neurons and glia, sympathetic ganglia

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7
Q

what do the pharyngeal arches form

A

much of the head an neck

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8
Q

when do the pharyngeal arches form

A

arch 1- day 22
arch 2 +3- day 24
arch 4+6- day 29

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9
Q

what is neuralation

A

formation of a round tube of neural cells

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10
Q

what number of pharyngeal arch doesnt form in humans

A

number 5

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11
Q

what are the three components of the pharyngeal apparatus

A

core pharyngeal arch
external pharyngeal cleft
internal pharyngeal pouch

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12
Q

what are the roles of the clefts and arches

A

separates the arches

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13
Q

what makes up the core pharyngeal arches

A

mesechymal tissue

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14
Q

what makes up the external pharyngeal cleft

A

ectoderm (as clefts on the outside)

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15
Q

what do the three germ layers form

A

ecto- central nervous system, peripheral nervous system, epithelia of eye, ear, nose, epidermis and appendages, mammary glands, enamel of teeth

meso- muscle, vasculature, lymph vessels, bone, connective tissue, kidneys, gonads

endo- epithial lining of GI and resp tracts, parenchyma of the tonsils liver thymus thyroid parathyroid pancreas, epithelial lining of bladder, tympanic cavity and antrum and auditary tube

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16
Q

what makes up the internal pharyngeal pouch

A

endo (as on the inside)

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17
Q

what makes up each pharyngeal arch

A

core mesenchyme derived from paraxial and lateral plate mesoderm

neural crest cells

cranial nerve component

artery (aortic arch arteries)

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18
Q

in the pharyngeal arch what does the core mesenchyme make

A

musculature of the face

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19
Q

in the pharyngeal arch what does the neural crest cells make

A

skeletal component of the face

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20
Q

in the pharyngeal arch what does the cranial nerve component make

A

innervation both sensory or motor

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21
Q

what nerves supply all the structures in the head and neck from pharyngeal arch 1

A

tigeminal nerve (V)- mandibular and maxillary divisions

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22
Q

what nerves supply all the structures in the head and neck from pharyngeal arch 2

A

facial nerve VII

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23
Q

what nerves supply all the structures in the head and neck from pharyngeal arch 3

A

glossopharyngeal nerve CN IX

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24
Q

what nerves supply all the structures in the head and neck from pharyngeal arch 4 and 6

A

vagus

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25
Q

what are the skeletal elements of the 1st pharyngeal arch

A

maxillary process (cranial portion):

  • maxilla
  • zygomatic bone
  • squamous portion of temporal bone

mandibular process (caudal portion):

  • forms meckels cartilage
  • incus and malleus (ear ossicles)
  • mandible
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26
Q

what are the muscles and nerves of the 1st pharyngeal arch

A

all musculature supplied by CNV3:

  • muscles of mastication
  • mylohyoid
  • anterior belly of digastric
  • tensor tympani
  • tensor veli palatini

sensory supply to skin of face:

  • V1 (ophthalmic)
  • V2 (maxillary)
  • V3 (mandibular)
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27
Q

what is the role of tensor tympani

A

dampens sound

28
Q

what are the skeletal elements of the 2nd arch

A

cartilage- reicherts cartilage

skeletal derivatives:

  • stapes
  • styloid process of temporal bone
  • stylohyoid ligament
  • lesser horn of hyoid
  • upper part of hyoid body
29
Q

what are the muscle and nerve elements of the 2nd pharyngeal arch

A

all musculature supplied by CN VI (facial nerve):

  • Muscles of facial expression
  • posterior belly of digastric
  • stylohyoid
  • stapedius
  • auricular muscles (move ears)
30
Q

what are the skeletal elements of the 3rd pharyngeal arch

A

greater horn pf hyoid bone

lower part of hyoid bone

31
Q

what are the muscle and nerve elements of the 3rd pharyngeal arch

A

stylopharyngeus
longitudinal pharyngeal muscle

supplied by the glossopharyngeal nerve

32
Q

what are the skeletal elements of the 4th and 6th pharyngeal arch

A

laryngeal cartilages

33
Q

what are the muscle elements of the 4th pharyngeal arch

A
  • cricothyroid
  • levator veli palatini
  • pharyngeal constrictors
34
Q

what are the muscle elements of the 6th pharyngeal arch

A

intrinsic laryngeal muscles (moves vocal chords)

35
Q

what are the nerve elements of the 4th and 6th pharyngeal arch

A

both supplied by vagus nerve

arch 4- superior laryngeal nerve, pharyngeal plexus

arch 6- recurrent laryngeal nerve

36
Q

what does the 1st pharyngeal cleft form

A

external acoustic meatus

37
Q

what do the 2-4th pharyngeal clefts form

A

lose contact with outside and form the cervical sinus

38
Q

what can happen if pharyngeal cleft 2 doesnt form properly

A

creates branchial sinus- bacteria can get in

can get internal fistulas

39
Q

what does the 1st pharyngeal pouch form

A

middle ear, tympanic membrane, eustachian tube

40
Q

what does the 2nd pharyngeal pouch

A

palatine tonsil

41
Q

what does the third pharyngeal pouch form

A

inferior parathryoid gland

thymus

42
Q

what does the fourth pharyngeal pouch form

A 
superior parathyroid gland 
ultimobranchial body (thyroid gland/ C-cells)
43
Q

what is the path of the thymus

A

Thymus lies on anterior mediastinum mostly then moves outwards.
As embryo starts to develop it will track its way down the way to thorax, unite with contralateral side and form thymus gland. Drags ifnferior parathyroid gland with it and develops over superior parathyroid gland which is derived from 4th pouch.
Thyroid gland descending down
Thymus drags down and drags parathyroid gland and lodges self in back of thyroid

44
Q

what are the parts of the inner ear and what do they do

A

balance (semicircular canals)

hearing (organ of corti)

45
Q

what makes up the middle ear

A

tympanic cavity

ossicles

46
Q

what makes up the external ear

A

external auditory meatus

auricle (pinna)

47
Q

what makes the otic placodes

A

ectoderm

48
Q

how do the otic vesicles form

A

otic placode- otic pit- otic vesicle

49
Q

what do the otic vesicles make

A

the inner ear

50
Q

what gives rise to the semicircular canals

A

utricular portion

51
Q

what gives rise to the cochlear

A

saccular portion

52
Q

what is endolymph and perilymph

A

endo fluid inside the membranous labyrinth of the ear

peri fluid inbetween the membranous labyrinth of the ears

53
Q

how do the semicircular canals form

A

at week 6 utricular portion starts to flatten itself out. Central area moves in. starts to create rings.

54
Q

what is the crus ampullare

A

dilated end of the semicircular canals

55
Q

what is the crus nonampullare

A

non dilated end of the semicircular canals

56
Q

what is the crista ampullaris

A

within the ampulla of the semicircular canals
contains:
sensory cells for balance
vestibular fibres CN VIII

57
Q

how does the cochlear duct develop

A

grows in spiral at weeks 6-8

surrounding mesenchyme becomes cartilagenous

58
Q

how many coils of the cochlea

A

2.5

59
Q

where is sound mostly conducted in the cochlear

A

organ of corti

60
Q

what forms the oval window

A

neural crest cells

61
Q

what forms the external auditory meatus

A

dorsal part of first pharyngeal cleft

62
Q

how is the external ear developed

A

Month 3 – epithelial cells proliferate to form Meatal Plug

Plug dissolves in month 7 and contributes to eardrum

6 mesenchymal proliferations (3 from arch 1, 3 from arch 2)
surround 1st pharyngeal cleft

Hillocks fuse to form definitve Auricle

External ears initially in lower neck

Ascend due to development of mandible

63
Q

what forms the internal layer of the external ear

A

tubotympanic recess

64
Q

what makes the intermediate layer of the external ear

A

neural crest cells

65
Q

what forms the external cartilage of the ear

A

neural crest cells

ENT (27 decks)

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