Embryo Of Head And Neck Flashcards

1
Q

Describe the cartilaginous component of the viscerocranium

A

First branchial arch (Meckel’s)
Second branchial arch (Reichert’s)
Third, fourth, and sixth branchial arch

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2
Q

Describe the membranous component of viscerocranium

A

Maxillary prominences of first branchial arch

Mandibular prominence of first branchial arch

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3
Q

Describe Apert Syndrome

A

Premature fusion of coronal sutures (craniosynotosis)
Causes skull deformities: acrocephalic (“tower skull”) appearance
Affects growth of brain

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4
Q

Describe the fontanelles

A

Anterior
Posterior
Anterolateral (sphenoidal)
Posterolateral (occipital)

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5
Q

Describe cranioschisis (acrania)

A

Represents failure of occipital and parietal bones to completely form or close
Usually associated with arrested brain development and rudimentary forebrain (anacephaly)

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6
Q

Describe microcephaly

A

Small cranium due to early fusion of cranial sutures

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7
Q

Describe macrocephaly

A

Enlarged cranium secondary to hydrocephaly

Early fusion of superior cranial sutures may result in a conical cranium

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8
Q

What is the most important event of development? Describe it

A

Gastrulation
Formation of trilaminar embryo
Cells come fro the epiblast

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9
Q

What occurs during the 4th week for primitive mouth and pharynx development?

A

Primitive pharynx induces evagination of ectoderm to form stomadaeum
Induced by rostral foregut entoderm

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10
Q

What separates the stomodeum from the endodermal foregut?

A

Oropharyngeal membrane (old prochordal plate)

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11
Q

The stomodeum is surrounded by five facial swellings which include what and what are they formed by?

A

Frontal (frontonasal) prominence (unpaired)
Maxillary prominences of arch I
Mandibular prominences of arch I
They are formed by mounds of mesenchyme and their overlying ectoderm

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12
Q

A portion of the skin ectoderm in the frontal (frontonasal prominence) thickens to form what?

A

Nasal placodes

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13
Q

What are formed by the proliferation of the mesenchyme beneath the medial and lateral edges of the nasal placodes?

A

Nasal prominences

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14
Q

What does the lateral nasal prominence form?

A

Alae of nose

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15
Q

What does the medial nasal prominence form?

A

Middle part of nose
Medial upper lip
Philtrum

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16
Q

What forms the primary palate?

A

Posterior (palatal) portion of intermaxillary segment

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17
Q

What is the nasal septum?

A

Midline down growth of fused medial nasal prominences

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18
Q

Nasal placodes invaginate to form ____, which enlarge into ____. Remaining space between this and oral cavity is ____, which ruptures to open nasopharynx to oropharynx

A

Nasal pits
Nasal sacs
Oronasal membrane

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19
Q

When does development of the face occur?

A

Weeks 5-10

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20
Q

Describe the nasolacrimal groove

A

Oblique furrow created between lateral nasal prominence and maxillary prominence

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21
Q

The ectoderm in the floor of the nasolacrimal groove thickens to form a cord. This cord separates from the surface and canalizes to form ___

A

Nasolacrimal duct

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22
Q

Describe the development of an oblique facial cleft

A

Due to failure of lateral nasal prominences and maxillary prominences to fuse.
Often associated with cleft chin and partial fusion of mandibular prominences
Nasolacrimal duct is exposed

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23
Q

What happens when the lateral nasal prominences and maxillary prominences fail to fuse?

A

Oblique facial cleft

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24
Q

What do maxillary prominences form?

A

Lateral parts of upper lip and jaw

Secondary palate or palatine shelves

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25
Q

Describe formation of muscles of facial expression (mimetic muscles)

A

Mesenchyme from branchial arch II invade into maxillary and mandibular swellings (arch I)

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26
Q

What innervates the muscles of facial expression?

A

Special visceral efferent (SVE) fibers from facial nerve (VII)

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27
Q

Special visceral efferent fibers innervate muscles of ___ origin

A

Branchiomeric

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28
Q

Pair branchial arches to their nerves

A

Arch I: trigeminal n
Arch II: facial n
Arch III: glossopharyngeal n
Arch IV: vagus n

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29
Q

What are muscles of mastication derived from?

A

Mesenchyme of arch I

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30
Q

What innervates muscles of mastication?

A

SVE fibers from mandibular division of trigeminal nerve

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31
Q

The ectoderm of facial swellings are innervated by what nerve?

A

Trigeminal n

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32
Q

The ophthalmic nerve (V1) supplies what?

A

GSA fibers to skin of frontonasal prominence

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33
Q

The maxillary nerve (V2) supplies what?

A

GSA fibers to skin of maxillary prominence

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34
Q

Mandibular nerve (V3) supplies what?

A

GSA fibers to skin of mandibular prominence

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35
Q

Mandibular prominence form what? What if they partially or completely fail to fuse?

A

Lower jaw and lip

Failure can result in cleft chin

36
Q

Medial nasal prominences fuse as ____ to form ___ and ___

A

Intermaxillary process
Nasal septum
Primary palate

37
Q

Oronasal membrane separates nasal sacs from primitive oral cavity. It breaks down to form ____

A

Primitive choanae

38
Q

Describe the incisive foramen

A

Marks boundary between junction of primary and secondary palates
Also distinguishes anterior from posterior cleft deformities

39
Q

Describe anterior cleft deformity

A

Results from failure of medial nasal and maxillary swellings to fuse

40
Q

Describe posterior cleft deformity

A

Results if palatine shelves do not fuse during development

41
Q

Describe median cleft lip and bifid nose

A

Failure of medial nasal prominences to fuse

Rare, may be autosomal recessive

42
Q

Describe macrostomia and microstomia

A

Dysfusion of maxillary and mandibular swellings

43
Q

What causes bilateral cleft defect?

A

Failure of intermaxillary segment to form

44
Q

List some holoprosencephalic defects of midface. Cause?

A

Cyclopia and extreme reduction of midface
Cebocephaly: single nostril
Absence of nose and hypoterlorism
Caused by fetal alcohol syndrome

45
Q

Describe the formation of branchial arches

A

Induced by neural crest migration into head and neck region
Each arch contains artery, nerve, muscle, and cartilage rod (will develop into bones/cartilages of lower face/neck)
Mesodermal core of arch is derived from intraembryonic mesoderm

46
Q

Match GSA, GVA, and SVE to germ layer

A

GSA: sensory to ectoderm (skin)
GVA: sensory to endoerm (like pharyngeal mucosa)
SVE: motor to skeletal muscles of branchiomeric origin

47
Q

What muscles form from branchial arch I?

A

Muscles of mastication
Anterior digastric
Tensor tympani
Tensor palatini

48
Q

What nerve innervates branchial arch I?

A

Trigeminal (V)

49
Q

What skeletal structures develop from branchial arch I?

A
*Incus, malleus*
Maxilla
Mandible
Meckel's cartilage
Anterior mallear ligament
Sphenomandibular ligament
50
Q

What is the artery of branchial arch I?

A

None. Degenerates

51
Q

What develops from the branchial groove of arch I?

A

Tympanic membrane

External auditory meatus

52
Q

What muscles develop from arch II?

A

Mimetic muscles (facial expression)
Posterior digastric
Stapedius
Stylohyoid

53
Q

What nerve innervates arch II?

A

Facial (VII)

54
Q

What skeletal structures develop form arch II?

A

Stapes
Hyoid (lesser cornu)
Reichert’s cartilage
Styloid process
Stylohyoid ligament

55
Q

Artery for arch II?

A

Degenerates

56
Q

What forms from the groove for arch II?

A

Anomalous cyst or fistulas

57
Q

What muscles develop from arch III?

A

Stylopharyngeus

58
Q

What nerve innervates arch III?

A

Glossopharyngeal (IX)

59
Q

What skeletal structures form from arch III?

A

Hyoid (body and greater cornu)

60
Q

What artery is derived from arch III?

A

Stem of internal carotid arteries

61
Q

What forms from groove for arch III?

A

Cervical sinus (?)

62
Q

What muscles derive from arch IV?

A

Pharyngeal muscles

Laryngeal muscles

63
Q

What nerve innervates arch IV?

A

Vagus (X)

64
Q

What skeletal structure develops from arch IV?

A

Laryngeal cartilages

65
Q

What arteries develop from arch IV?

A

Left: aortic arch
Right: subclavian

66
Q

What can form from the groove for arch IV?

A

Cervical sinus (?)

67
Q

What nerve innervates arch VI?

A

Recurrent laryngeal n (Vagus)

68
Q

Describe Treacher Collins Syndrome

A

First arch syndrome
Impaired growth of midface
Deformities may include small chin, enlarged nose, cleft palate, and cleft lip
About 40-50% experience some conductive hearing loss due to underdevelopment of ossicles and usually affects both ears equally

69
Q

Describe formation and development of primitive pharynx

A

Formed by rostral dilation of foregut
Develops four pairs of lateral diverticulae called pharyngeal pouches
Pouches are in between arches (1st pouch between 1st and 2nd arches, etc)

70
Q

Describe branchial membranes

A

Endodermal pouches extend laterally and contact ectoderm of branchial grooves

71
Q

The first branchial membrane persists as the ___

A

Tympanic membrane (pouch I)

72
Q

What are derivatives from the first branchial pouch?

A

Eustachian tube
Tympanic cavity
Mastoid air cells
Tongue (body)

73
Q

What are the derivatives from the second branchial pouch?

A

Palatine tonsils
*Tongue (root)
Pharyngeal tonsil
Lingual tonsil

74
Q

What are the derivatives from the third branchial pouch?

A

Inferior parathyroid gland
Ventral portion: thymus
Tongue

75
Q

What are the derivatives from the fourth branchial pouch?

A

Superior parathyroid gland
Ultimobranchial body
Parafollicular cells (thyroid gland)

76
Q

What are the fates of the pharyngeal clefts?

A

First cleft: external auditory meatus

Second arch expands and fuses with cardiac eminance to cover remaining clefts (transient cervical sinus)

77
Q

Describe abnormal cysts produced by lateral cervical sinus or first pharyngeal cleft

A

Isolated cervical cyst
Cervical cyst with external fistula
Cervical cyst with internal fistula
Cervical cyst with both internal and external fistula

78
Q

Describe aural cysts

A

May form anterior to ear

Anomalous derivatives of first pharyngeal cleft

79
Q

Describe lateral cervical cysts

A

Located anterior to sternocleidomastoid muscle

80
Q

Describe development of thyroid gland

A

Thyroid diverticulum evaginates and descends in neck (partially attributable to tongue growth)
Initially, thyroglossal duct connected migrating thyroid to tongue at foramen cecum
Diverticulum solidifies, and lobes bud off
Some glandular ofter persists along midline as pyramidal lobe

81
Q

Describe remnants of early migration of thyroglossal duct

A

Thyroglossal duct cysts and sinuses may develop

Remnants may also include ectopic thyroid tissue

82
Q

Describe development of anterior two-thirds of tongue

A

Lateral lingual swellings (arch I) overgrow median tuberculum impar and fuse in midline

83
Q

Describe development of posterior one-third of tongue

A

Hypobranchial eminence (arch III) overgrows copula (arch II)

84
Q

What innervates the anterior 2/3 of tongue?

A
Trigeminal nerve (GSA)
Facial nerve (SVA taste)
85
Q

What innervates the posterior 1/3 of tongue?

A

Glossopharyngeal nerve (GVA and SVA)

86
Q

What innervates the intrinsic muscles of tongue?

A

Hypoglossal nerve (GSE)

87
Q

Describe the neurocranium

A

During first 10 weeks, the cartilaginous neurocranium cradles the base of the skull.
At the end of this period, the flat bones start to form membranous neurocranium