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Fundamentals of Patient Management > BSC Embryo 2 > Flashcards

BSC Embryo 2 Flashcards

1
Q

what is the overall event happening during week 3

A
  • cells of the epiblast begin to invaginate
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2
Q

what are the 2 waves of gastrulation during week 3

A
  • 1st wave: cells migrate through the streak interdigitate with the hypoblast layer -> ENDODERM
  • 2nd wave -> MESODERM
  • remaining cells in the epiblast layer for the ECTODERM
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3
Q

what is the name of process occurring with the ectoderm

A

neurelation

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4
Q

what is neurulation

A

notochord signals neural tube formation and results in the ectoderm dividing into 3 sets of cells

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5
Q

what are the three sets of cells that the ectoderm divides into

A

1) neural tube
2) neural crest cells
3) epidermis

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6
Q

what is the highlight of neural crest cells

A

cranial neural crest leads to cartilage, bone, cranial ganglia & CT of the face

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7
Q

which cells form the mesoderm

A

cells migrating in the 2nd wave of gastrulation

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8
Q

what forms the notochord*

A

some mesoderm cells condense to form it

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9
Q

what is the notochord essential for?

A

guiding adjacent mesoderm cells to differentiate into specialized types

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10
Q

what are the 4 specialized types that adjacent mesoderm cells differentiate into

A

1) paraxial mesoderm*
2) intermediate mesoderm
3) lateral plate mesoderm*
4) extraembryonic mesoderm

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11
Q

what is the location of the paraxial mesoderm?

A

closest to the notochord

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12
Q

what structure does the paraxial mesoderm form

A

forms structures of the head and somites

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13
Q

what are somites?

A

paired tissue blocks forming adjacent to the notochord

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14
Q

how often are somites formed? how many are there total?

A

~ 3 pairs form per day from cranial to caudal
42-44 pairs total

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15
Q

what are the resulting structures of the paraxial mesoderm

A
  • vertebrae, ribs, rib tendons*
  • muscles of the back, ribs, and limbs*
  • parts of the dermis*
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16
Q

what is the main event during head and neck development

A

FORMATION OF PHARYNGEAL APPARATUS
- CONSISTS OF PHARYNGEAL (BRANCHIAL) ARCHES, POUCHES, AND CLEFTS

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17
Q

when does the pharyngeal apparatus appear?

A

4th- 5th week of development

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18
Q

what are the prominences and layers of the pharyngeal apparatus

A
  • 5 paired prominences
  • 3 layers: an outer covering of ectoderm, an inner covering of endoderm, and a middle core of mesenchyme*
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19
Q

where do the pharyngeal clefts derive from

A

ectoderm

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20
Q

where do pharyngeal pouches arise from

A

endoderm

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21
Q

where do pharyngeal arches arise from

A

mesoderm

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22
Q

how many pharyngeal arches are there? what’s the catch?

A
  • 6 arches
  • no 5th arch! the 5th arch is transient. it involutes and produces no adult structures*
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23
Q

what does each pharyngeal arch have?

A
  • core of mesenchyme that develops into arterial supply, nerve supply, cartilage, musculature & bone
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24
Q

define mesenchyme

A

an embryonic precursor tissue that generates a range of structures in vertebrates including cartilage, bone, muscle, and the erythropoietic system

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25
Q

which are major contributors to the mesenchyme of head and neck development

A
  • paraxial and lateral plate mesoderm
  • neural crest cells
  • thickened regions of ectoderm called ectodermal placodes
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26
Q

what is the clinical connection of pharyngeal arches

A
  • “tumors of mesenchymal origin”
  • a tumor arising from the supporting mesenchymal (ex: fibrous, CT, blood vessels, lymphatics, nerves, adipose tissues and muscle)
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27
Q

where do cranial neural crests cells migrate

A

in the pharyngeal arches and face

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28
Q

what are 2 alternative names for ectodermal thickenings

A

1) ectodermal placodes
2) epipharyngeal placodes

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29
Q

what is the job of ectodermal thickenings

A

assist crest cells in formation of the fifth (V), seventh (VII), ninth (IX), and tenth (X) cranial sensory ganglia [group of neuronal cell bodies]

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30
Q

what does each pharyngeal arch get supplied by

A

its own cranial nerve

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31
Q

what 5 prominences initially make up the face

A

*1 central frontonasal prominence
*2 paired maxillary prominences
*2 paired mandibular prominences

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32
Q

what is the stomodeum

A

structures that surround the primitive mouth

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33
Q

where is the structure of the stomodeum initially

A

sealed by the oropharyngeal membrane which breaks down by day 30

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34
Q

what is the name of the 1st
pharyngeal arch

A

*the mandibular arch

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35
Q

which prominences arise from the 1st pharyngeal arch

A

maxillary and mandibular prominences*

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36
Q

what is the *maxillary process

A

mesenchyme here -> premaxilla, maxilla, zygomatic bone and part of the temporal bone

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37
Q

what is the mandibular process*

A
  • contains meckel cartilage* -> contributes to incus and malleus and serves as a template for mandible formation
  • mesenchyme here -> mandibular bone*, part of external ear, *incus and *malleus bones of the middle ear and *external auditory meatus
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38
Q

what muscles belong to the 1st mandibular arch

A

**muscles of mastication (Masseter, Temporalis, Lateral pterygoid, Medial pterygoid)

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39
Q

*what is the nerve supply of the 1st pharyngeal arch

A

motor and sensory from branches of *trigeminal nerve (CN V)

40
Q

what is the name of the 2nd pharyngeal arch

A

*hyoid arch

41
Q

what is the cartilage component of the 2nd pharyngeal arch

A
  • *Reichert cartilage
42
Q

describe *Reichert cartilage

A

precursor to the stapes, the styloid process, the stylohyoid ligament and parts of the hyoid bone & most of external ear

43
Q

what are the *muscles of the 2nd arch

A

muscles of facial expression, stapedius, stylohyoid, posterior belly of the digastric, and auricular

44
Q

what is the nerve supply for the 2nd pharyngeal arch

A

Facial nerve (CN 7)

45
Q

what are the components of the 3rd pharyngeal arch

A

small components of the hyoid bone

46
Q

what are the muscles of the 3rd arch*

A

stylopharyngeus muscle *

47
Q

what is the stylopharyngeus muscle

A
  • muscles of the pharynx
  • functions in swallowing
48
Q

what is the nerve supply for the 3rd arch*

A

*glossopharyngeal nerve (CN IX)

49
Q

what are the components of the 4th and 6th arch

A

cartilaginous components

50
Q

what do the cartilaginous components of the 4th and 6th arch fuse to form*

A

thyroid, cricoid, arytenoid, corniculate, and cuneiform CARTILAGES of the larynx *

51
Q

what are the muscles of the fourth arch

A

cricothyroid, levato veli palatini, and constrictors of the pharynx

52
Q

what is the nerve that supplies the 4th and 6th arches*

A

branches of vagus (CN X)

53
Q

how many pharyngeal pouches are there

A

4 pairs of pharyngeal pouches

54
Q

what are the pharyngeal pouches lined by

A

epithelial from the endoderm layer

55
Q

what are the structures that result from the 1st pharyngeal pouch

A
  • middle ear cavity*
  • auditory (eustachian) tube*
  • tympanic membrane (eardrum)*
56
Q

what occurs with the 2nd pharyngeal pouch

A

endoderm of the pouch proliferates and forms buds that penetrate surrounding mesenchyme

57
Q

what are 3 features of the 2nd pharyngeal pouch

A
  • mesodermal tissue enters buds and forms palatine tonsil*
  • months 3-5 tonsil is infiltrated by lymphatic tissue*
  • remnants of pouch create tonsillar fossa
58
Q

which structures arise from the 3rd pharyngeal pouch

A
  • dorsal region of the third pouch differentiates into the inferior parathyroid gland*
  • ventral region of the third pouch differentiates into the thymus*
59
Q

what do the dorsal and ventral region of the 4th pharyngeal pouch develop into

A

dorsal -> superior parathyroid gland
ventral -> ultimobranchial body

60
Q

what are 2 features of the ultimobranchial body

A
  • ultimobranchial body later incorporated into the thyroid gland
  • cells of the ultimobranchial body gives rise to the parafollicular cells (C cells) of the thyroid gland that secrete calcitonin
61
Q

what do some texts call the 1st cleft

A

external auditory meatus

62
Q

what do the 2nd, 3rd, and 4th clefts merge to form? what occurs to this?

A
  • cervical sinus
  • cervical sinus normally disappears during development
63
Q

when does the tongue appear in the embryo

A

~ 4weeks

64
Q

what are the origins of tissue for the tongue

A

*from first arch: formation of anterior 2/3 of tongue aka body of the tongue
* from 2nd, 3rd, & 4th arch: posterior 1/3 tongue

65
Q

what are the 3 swellings of the tongue

A

these are all anterior and come from 1st arch
- 2 lateral swellings: lingual swellings
- 1 medial swelling: tuberculum impar

66
Q

what is the swelling that comes from the 2nd, 3rd, and 4th arch

A

1 medial swelling: copula (hypobranchial eminence)

67
Q

describe the innervation of the anterior 2/3 of the tongue

A

*sensory innervation is a branch of CN V because these structures originate from the 1st pharyngeal arch

68
Q

what separates the anterior 2/3 of the tongue from the posterior 1/3

A

V-shaped groove called terminal sulcus

69
Q

describe the innervation of the posterior 1/3 of the tongue

A

*sensory innervation by glossopharyngeal nerve, CN IX

70
Q

what is an important sensory feature of the tongue

A

*additional special sensory innervation (taste)

71
Q

where does the epiglottis originate from

A
  • tissue of the 4th pharyngeal arch*
  • epiglottal swelling*, swelling posterior to copula (posterior 1/3 of tongue)
72
Q

what innervates the epiglottis

A

branch of Vagus nerve, CN X

73
Q

where does the tissue for the thyroid gland originate from

A
  • endoderm between first and second pharyngeal pouches*
74
Q

what are the 3 development steps for the thyroid

A

1) proliferation begins at juction of anterior 2/3 tongue and posterior 1/3 of tongue
- leaves behind a depression called foramen cecum
2) thyroid descends from tongue to final position in the neck ~7th week
3) thyroid remains connected to the tongue by a narrow canal, the thyroglossal duct, which should disappear during development

75
Q

when does the thyroid gland begin to function

A
  • at approx. the end of the third month (10-12 wks)
76
Q

what are the 5 birth defects*

A

1) hemifacial microsomia (oculoauriculovertebral spectrum or Goldenhar syndrome)
2) branchial cleft cyst (lateral cervical cyst/ cervical lymphoepithelial cyst)
3) thyroglossal duct cyst and fistula
4) lingual thyroid
5) tongue tie (ankyloglossia)

77
Q

what are a couple of features of hemifacial microsomia

A
  • abnormal development in 1st and 2nd pharyngeal arch structures
    -*cause is unknown
78
Q

what are the clinical features of hemifacial microsomia

A
  • *under-development of the oral-facial area, usually one-side only
  • other defects in ~50% of cases
    ->* other cardiac defects: tetralogy of Fallot, ventricular septal defects
79
Q

how does branchial cleft cyst develop

A

improper involution of any of the branchial clefts leaves behind epithelium that can -> branchial cleft cyst formation

80
Q

where can branchial cleft cyst occur

A

*anywhere along the anterior sternocleidomastoid muscle
- depends on which cleft fails to involute
- *most commonly the second cleft

81
Q

how does the branchial cleft cyst develop over time

A

frequently not visible at birth but becomes evident as it enlarges during childhood

82
Q

what is the clinical presentation of the branchial cleft cyst

A
  • painless, compressible, *lateral neck mass
  • cyst may form a channel to the surface to drain= *draining sinus tract
83
Q

what can cause a branchial cleft cyst to enlarge

A

can be secondarily infected and cause enlargement in rare cases

84
Q

why does the thyroglossal duct cyst occur

A
  • if thyroglossal tract doesn’t involute entirely
    -> *remnants of tissue can develop into cysts along the tract
85
Q

what are clinical features of the thyroglossal duct cyst

A
  • *MIDLINE neck mass, *occurs anywhere along the descending tract
  • *typically present in 1st-2nd decade of life
  • *painless, fluctuant, moveable swelling
  • *moves with swallowing and elevates with protrusion of the tongue
86
Q

what is a requirement of they thyroglossal duct cyst

A

MUST BE IN MIDLINE

87
Q

what are two alternative names for the lingual thyroid

A

1) ectopic thyroid
2) aberrant thyroid tissue

88
Q

what is the etiology of a lingual thyroid

A
  • primitive thyroid gland doesn’t descend normally/ remnants of gland are left behind
  • of all ectopic thyroids, *90% are found between foramen cecum and epiglottis
  • on autopsy: small remnants of thyroid tissue present present on the posterior dorsal tongue in ~10% of both men and women (asympt.)
89
Q

how common are clinically evident/ symptomatic lingual thyroids?

A

uncommon

90
Q

what is the frequency of lingual thyroid?

A

4-7x more frequent in females

91
Q

what are symptoms of lingual thyroid? when do they start?

A

-*dysphagia, dysphonia, and dyspnea
- start during hormone shifts (ex: puberty, adolescence, pregnancy, or menopause)

92
Q

what happens for 70% of cases for lingual thyroid?

A

ectopic gland is the patient’s *only thyroid tissue

93
Q

what is ankyloglossia

A

condition in which degeneration does not occur properly causing “tongue-tie”

94
Q

describe important details of ankyloglossia

A
  • *extensive cell degeneration should occur at the floor of the month during development to release the tongue
  • *only a small frenulum should remain to attach tongue
95
Q

what are examples of the ankyloglossia

A
  • kotlow classification
  • functional classification systems
96
Q

what are the symptoms in adults for tongue tie

A

mostly speech difficulties

97
Q

what are the symptoms in infants for tongue tie

A
  • frequent, unfulfilling attempts at nursing
  • colic, reflux and gassy infant
  • failure to gain weight and thrive
  • calloused or blistered upper and lower lips
  • unstained latch

Fundamentals of Patient Management (10 decks)

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