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Cranio Exam 3 > development of thyroid gland, tongue, and ear > Flashcards

development of thyroid gland, tongue, and ear Flashcards

1
Q

what is the first endocrine gland to develop in the embryo?

A

thyroid gland

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2
Q

when does thyroid gland development begin?

A

24 days after fertilization

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3
Q

the thyroid gland develops from a median endodermal thickening in the ___________

A

floor of a primordial pharynx

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4
Q

thyroid primordium

A

small outpouching that develops from the thickening in the floor of the primordial pharynx

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5
Q

the thyroid primordium comes from which pharyngeal pouch?

A

2nd

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6
Q

thyroglossal duct

A

narrow tube connecting the thyroid gland to the tongue that eventually dissolves

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7
Q

how are the two lobes of the thyroid gland connected?

A

isthmus of the thyroid gland

-lies anterior to the developing second and third tracheal rings

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8
Q

by what week does the thyroid assume definitive shape and reach its final site in the neck?

A

seventh week

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9
Q

the thyroglossal duct has normally degenerated by what week?

A

seventh week

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10
Q

foramen cecum

A

the proximal opening of the thyroglossal duct that persists

-small pit in tongue

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11
Q

the pyramidal lobe extends upward from the isthmus in about _____% of people

A

50%

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12
Q

levator of thyroid gland

A

fibrous tissue or smooth muscle that attaches the pyramidal lobe to the hyoid bone

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13
Q

the pyramidal lobe and associated smooth muscle represent a persistent part of the distal end of the _____

A

thyroglossal duct

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14
Q

site of origin of thyroglossal duct between floor of branchial arches 1 and 2

A

foramen cecum

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15
Q

what does the thyroid primordium consist of?

A

solid mass of endodermal cells

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16
Q

what does the cellular aggregation of the thyroid primordium break up into?

A

a network of epithelial cords

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17
Q

by what week do the cords divide into small cellular groups?

A

10

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18
Q

what forms in each cell cluster of the thyroid when the cells become arranged in a single layer?

A

lumen

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19
Q

what happens during the 11th week in thyroid development?

A

colloid begins to appear in each cell called thyroid follicles and iodine concentration and synthesis of thyroid hormones can be demonstrated

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20
Q

thyroid secretion reaches adult level by how many weeks?

A

35 weeks

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21
Q

congenital hypothyroidism (cretinism)

A

most common metabolic disorder in neonates

-common cause of intellectual disability

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22
Q

causes of congenital hypothyroidism

A

agenesis–failure of normal development of thyroid gland

ectopic thyroid–situated in a different location (e.g. beneath tongue)

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23
Q

signs and symptoms of congenital hypothyroidism

A
  • retarded physical and mental growth
  • spine curved and height is less than 3 ft
  • head is large with wiry hair
  • thick eyelids and large tongue
  • abdomen protruding and sexual maturity not seen
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24
Q

treatment of congenital hypothyroidism

A

levothyroxine given to children

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25
Q

ectopic thyroid

A

thyroid develops in abnormal position
-mostly along course of thyroglossal duct
1/4000 people

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26
Q

most common site for ectopic thyroid

A

lingual

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27
Q

accessory thyroid gland tissue is–

A

lateral to thyroid cartilage

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28
Q

anomalies related to thyroglossal duct

A

cyst
sinus
fistula

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29
Q

t/f the thyroglossal duct disappears

A

true

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30
Q

what causes a thyroglossal cyst?

A

remnant of duct persists and forms a cyst in the tongue or anterior neck

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31
Q

thyroglossal cyst

A

painless, progressively enlarging, moveable mass

  • observed at 5 yrs
  • inferior to hyoid bone
  • may contain thyroid tissue
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32
Q

thyroglossal duct sinus

A

following infection of a cyst
perforation of the skin
opens in the median plane of the neck, anterior to the laryngeal cartilages

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33
Q

thyroglossal duct may remain patent and open into external surface causing a —

A

fistula

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34
Q

arch development of tongue

A

arch 1– oral part of tongue (anterior 2/3)
arch 2–initial contribution to surface is lost
arch 3–pharyngeal part of tongue (posterior 1/3)
arch 4–epiglottis and adjacent regions

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35
Q

development of anterior 2/3 of tongue

A
  • 3 swellings from 1st arch
  • proliferation of mesenchyme in ventromedial parts of the 1st pair of pharyn arches
  • median tongue bud (elevation) appears in floor of primordium pharynx near end of 4th week, just in front of foramen cecum–> swelling is first indication of tongue
  • 2 oval distal tongue buds develop on each side of the median tongue bud
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36
Q

what grows over the median tongue bud?

A

lateral tongue buds increase in size and merge together overgrowing the median tongue bud

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37
Q

what forms the anterior 2/3 of the tongue?

A

merged distal tongue buds

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38
Q

how is the fusion of the distal tongue bud indicated?

A

a middle groove, the median sulcus of the tongue and internally by fibrous lingual septum
(median tongue bud forms no recognizable part of the adult tongue)

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39
Q

2 elevations that develop caudal to the foramen cecum to form the posterior 1/3 of tongue?

A
  1. copula: forms by fusion of ventromedial part of the 2nd pair of pharyngeal arches
  2. hypopharyngeal eminence: develops caudal to the copula from mesenchyme in ventromedial parts of the 3rd and 4th pairs of pharyngeal arches
40
Q

what happens to the copula as the tongue develops?

A

gradually overgrown by the hypopharyngeal eminience and disappears

41
Q

the pharyngeal part of the tongue develops from what?

A

the remaining part of the hypopharyngeal eminence

42
Q

terminal sulcus

A

line of fusion of anterior and posterior parts of tongue

-v shaped

43
Q

pharyngeal mesenchyme

A

connective tissue and vasculature of tongue

44
Q

occipital myotomes

A

most of tongue muscles from myoblasts that migrate from occipial mytomes

45
Q

innervates tongue muscles as they develop

A

hypoglossal nerve (XII)

46
Q

the entire tongue is within the mouth at birth, its posterior third descends into the oropharynx by —– yrs old

A

4

47
Q

tongue muscles are from ______ occipital myotomes

A

3,4,5

48
Q

lingual papillae appear toward the end of the —- week

A

8

49
Q

what kind of nerve endings do lingual papilla contain

A

afferent nerve endings

50
Q

what papilla appear first

A

vallate and foliate

close to the terminal branches of glossopharyngeal nerve IX

51
Q

filiform papillae

A

most common
threadlike shape
develp during early fetal period (10-11 wks)

52
Q

when do fungiform papillae form?

A

later near termination of chorda tympani branch

53
Q

when do taste buds develop

A

11-13 wks by active interaction bw epithelial cells of tongue and invading gustatory cells from chorda tympani and glossopharyngeal and vagus nerves

54
Q

when is there a fetal response to bitter taste?

A

26-28 weeks

55
Q

anterior 2/3 of tongue nerve supply

A

lingual branch of mandibular division of trigeminal

56
Q

taste for anterior 2/3

A

chorda tympani except vallate papillae which are innervated by glossopharyngeal nerve (IX)

57
Q

motor for anterior 2/3

A

hypoglossal

58
Q

common sensation of tongue

A

trigeminal

59
Q

nerve of 1st pharyngeal arch and this arch forms the median and distal tongue buds

A

trigeminal

60
Q

nerve of second phar arch

A

facial

61
Q

palatoglossus is supplied by?

A

vagus

62
Q

the posterior 3rd of tongue is innervated by ?

A

glossopharyngeal from 3rd arch

63
Q

superior laryngeal branch of vagus supplies?

A

small area of tongue anterior to epiglottis

64
Q

the vagus nerve is of the — arch

A

4

65
Q

all muscles of the tongue are supplied by _____ except for _____

A

all by hypoglossal except palatoglossus which is supplied from pharyngeal plexus by fibers from vagus nerve

66
Q

aglossia

A

no tongue

feeding, breathing, and speech issue

67
Q

bifid tongue

A

failure of fusion of 2 lateral lingual swelling

68
Q

congenital lingual cyst of fistula

A

persistent lingual part of thyroglossal duct

69
Q

tongue tie (ankyloglossia)

A

short, thick band of tissue which connects the lip of tongue to floor of mouth and restricts movement of tongue

70
Q

microglossia

A

small tongue

-with microgenitalia and limb defects

71
Q

macroglossia

A

large tongue

  • trisomy 21
  • acromegaly
  • mucopolysaccharidoses
  • congential hypothyroidism
  • diabetes
72
Q

3 anatomical parts of ear

A
  1. external –auricle, external auditory meatus, outer layer of tympanic membrane
  2. middle–3 auditory ossicles (stapes, incus, malleus), inner layer of tympanic membrane
  3. internal–vestibulocochlear organ (cochlea and semicircular canal)
73
Q

external auditory canal develops from–

A

surface ectoderm that covers the dorsal end of the 1st pharyngeal groove

74
Q

meatal plug

A

solid epithelial plate that develops at bottom of funnel shaped pharyngeal groove

75
Q

what lines the middle ear?

A

1st pharn pouch endoderm

76
Q

eustachan tube

A

connects pharynx to ear

77
Q

malleus and incus form from the mesoderm of the — arch

A

1st arch

mechel’s cartilage

78
Q

stapes forms from

A

mesoderm of 2nd arch

reichert’s cartilage

79
Q

ossicles are full sized by ____

A

15 weeks

80
Q

ossicles ossify by

A

25 weeks

81
Q

tensor tympani supplied by —

A

mandibular nerve (1st arch)

82
Q

stapedius supplied by

A

facial nerve (2nd arch)

83
Q

the first brachial arch is also called

A

mandibular arch

84
Q

second arch is called

A

hyoid arch

85
Q

in between 1st and 2nd brachial arch is called the

A

ectodermal cleft

86
Q

ectoderm of internal ear

A

membranous labyrinth

87
Q

bony labyrinth

A

mesoderm of internal ear

88
Q

what happens in the 3rd week of internal ear development?

A

surface ectoderm–otic placode invaginates into otic pit

89
Q

4th week in ear development

A

pit edges fuse to become otic vesicle (primordium of membranous labyrinth)

90
Q

otic vesicle separates from surface ectoderm, elongates, and forms the _____

A

endolymphatic duct and sac

91
Q

dorsal utericular part of ear

A

forms endolymphatic and semicircular ducts and utericle

92
Q

ventral saccular part of ear

A

forms saccules and cochlear duct

93
Q

congenital deafness

A

inner ear deafness (rubella)

middle ear deafness, anomalies of 1st and 2nd arches

94
Q

auricular anomalies of ear

A

accessory auricle, absence of auricle, small auricle

95
Q

atresia of external auditory meatus

A

failure of canalization

96
Q

congenital cholestotoma

A

keratin filled cysts that grow medial to tympanic membrane result either from birth abnormality, trauma or metaplasia

97
Q

what criteria do conditions need to fulfill in order for them to be a congenital ear disorder?

A
  1. mass medial to tympanic membrane
  2. normal tympanic membrane
  3. no previous history of ear discharge, perforation, or surgery

Cranio Exam 3 (9 decks)

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