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Anatomy PEDO > Embryology of the Face and Skull > Flashcards

Embryology of the Face and Skull Flashcards

1
Q

Development of the head and neck begins during ___ as ___ cells that pass through the primitive node and primitive pit begin to organize themselves as the ___ and ___ plate caudal to the ___ membrane.

A

gastrulation; epiblast; notochord; prechordal; oropharyngeal

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2
Q

As the notochord forms in the cranial to caudal direction, the overlying neural plate begins to fold into what?

A

Neural tube

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3
Q

The mesoderm immediately adjacent to the neural tube on either side becomes organized into thickened columns of ___ ___.

A

paraxial mesoderm

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4
Q

The isthmus signaling center forms at the level of the midbrain/hindbrain boundary and the hindbrain becomes segmented into how many rhombomeres?

A

8

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5
Q

Signals from the notochord and hindbrain induce formation of the __ __ from surface ectoderm lateral to the presumptive hindbrain (specifically adjacent to rhombomeres __ and __.)

A

otic placode; 5; 6

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6
Q

Caudal to the otic placode, the paraxial mesoderm becomes further organized into ___ and the more lateral mesoderm becomes organized into ___ mesoderm and ___ ___ mesoderm.

A

somites; intermediate; lateral plate

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7
Q

T/F: Cranial to the otic placode, the paraxial mesoderm remains as an unsegmented single column, and the intermediate and lateral plate mesoderm form.

A

FALSE: Cranial to the otic placode, the paraxial mesoderm remains as an unsegmented single column, and the intermediate and lateral plate mesoderm DO NOT form.

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8
Q

With differential growth of the brain vesicles, what happens when the forebrain overgrows the oropharyngeal membrane and the anterior head region folds ventrally?

A

The oropharyngeal membrane is brought ventrally (along with the precardiac mesenchyme and septum transversum), and pinching off the foregut (primitive pharynx) for the yolk sac.

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9
Q

During neurulation, what happens to neural crest cells?

A
  1. undergo an epithelial-to-mesenchymal transformation
  2. lose cell-to-cell adhesiveness
  3. Migrate away from the neural tube
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10
Q

T/F: Some of the neural crest cells that leave the cranial neural folds will migrate along stereotypical dorsolateral, ventrolateral and ventral pathways and differentiate as neurons of the sensory and autonomic ganglia, or as the melanocytes of the face and scalp.

A

TRUE

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11
Q

Neural crest cells from the cranial neural tube will give rise to __ __ cells of the carotid body and the ___ cells of the thyroid gland.

A

type I; parafollicular

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12
Q

How are the pharyngeal (branchial or visceral) arches formed?

A

Cranial neural crest (CNC) cells leave the neural folds in large streams to surround the primitive pharynx and begin proliferating

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13
Q

T/F: A total of 6 swellings form (numbered 1-6 in a cranio-caudal direction) but the sixth arch degenerates soon after it forms.

A

FALSE; A total of 6 swellings form (numbered 1-6 in a cranio-caudal direction) but the FIFTH arch degenerates soon after it forms.

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14
Q

CNC from rhombomeres 1 and 2 and the caudal midbrain populate the 1st arch as known as what?

A

mandibular arch

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15
Q

CNC from rhombomere ___ populates the second arch, aslo known as what?

A

4; hyoid arch

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16
Q

CNC from rhombomere 6 and 7 populate what arches?

A

3, 4, and 6.

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17
Q

Neural crest cells that migrate from cranial midbrain and caudal forebrain populate the ___ ___ which borders the oropharyngeal membrane cranially.

A

frontonasal prominence

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18
Q

What is the oropharyngeal membrane bounded by?

A

the mandibular arch

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19
Q

As swellings continue to expand the define the ___ (primitive mouth) of the embryo.

A

stomodeum

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20
Q

How are the pharyngeal arches separated from one another externally and internally?

A

externally - pharyngeal grooves

internally - pharyngeal pouches

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21
Q

What is the lining of the pharyngeal grooves? internal pharyngeal pouches?

A

surface ectoderm; foregut endoderm

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22
Q

Each ectodermal pharyngeal groove corresponds with each endodermal pharyngeal pouch, with a layer of what intervening?

A

mesenchyme

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23
Q

The core of each arch is composed of mesenchyme derived from what two sources?

A
  1. the CNC derived mesenchyme or ectomesenchyme

2. paraxial mesoderm

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24
Q

The ectomesenchyme will give rise to all of the connective tissues of what?

A

the face except the enamel of the teeth (eg. bone, dentin, cartilage, connective tissue sleeves of cranial musculature)

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25
Q

T/F: Connective tissues of the neck are formed from what?

A

ectomesenchyme and lateral plate mesoderm

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26
Q

What mesoderm gives rise to most of the head and neck musculature?

A

paraxial mesoderm

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27
Q

Each pharyngeal arch contains a central ___ rod that forms the skeleton of each arch.

A

cartilage

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28
Q

Each pharyngeal arch contains a vascular component, an ___ ___ artery that runs around the pharynx from the ventrally located heart to the dorsal aorta.

A

aortic arch

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29
Q

Each pharyngeal arch contains a ___ element, consisting of sensory and special visceral motor fibers of one or more cranial nerves, that what?

A

nervous; all of the derivatives of that arch

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30
Q

What pair of pharyngeal grooves contributes to adult structures?

A

the first pair

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31
Q

The dorsal end of the first pair of pharyngeal grooves deepens to form the what structure? The ecto-meso-endodermal membrane in the depth of the groove persist as what?

A

external acoustic meatus; tympanic membrane

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32
Q

How does a cervical cyst or cervical fistula form?

A

the remaining grooves become obliterated by a caudal overgrowth of the second arch that provides a smooth contour to the neck and forms the cervical sinus. If this sinus does not becomes obliterated as the neck development continues a cyst or fistula may form.

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33
Q

The first pharyngeal pouch expands into an elongate ___ ___ that will form the tympanic cavity (separated from the ___ pharyngeal groove by the tympanic membrane) and the ___ antrum.

A

tubotympanic recess; mastoid

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34
Q

The connection of the first pharyngeal pouch with the pharynx gradually elongates to form what?

A

the auditory tube

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35
Q

The dorsal portion of the second pharyngeal pouch persists in an attenuated form as the ___ fossa, the endodermal lining of which differentiates as the ___ ___.

A

tonsillar; palatine tonsil.

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36
Q

Each dorsal portion of the ___ pharyngeal pouch differentiates into an ___ ___ gland.

A

third; inferior parathyroid

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37
Q

T/F: The ventral portion of the third pharyngeal pouch fuses with the opposite side to form the inferior parathyroid gland.

A

FASLSE; The ventral portion of the third pharyngeal pouch fuses with the opposite side to form the THYMUS.

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38
Q

As they migrate caudally, the parathyroid glands separate from the thymus gland and reach the dorsal surface of the thyroid gland which has descended from the developing ___.

A

tongue

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39
Q

What does the fourth pharyngeal’s dorsal portion develop into?

A

a superior parathyroid gland.

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40
Q

This pouch appears as a diverticulum of the fourth pouch and develops into the ultimobranchial body (or postbranchial body), which is the source of the parafollicular cells of the thyroid gland.

A

Fifth pharyngeal pouch

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41
Q

The ___ initially appears as a median endodermal thickening in the floor of the primitive pharynx between the first and second pouches. What happend shortly after this?

A

thyroid; the thyroid primordium descends through the tissues of the neck

42
Q

T/F. Early in its descent, the thyroid primordium remains connected to the pharynx by the thyroglossal duct.

A

TRUE.

43
Q

What is the final destination of the thyroglossal duct?

A

just inferior to the cricoid cartilage of the larynx

44
Q

What are remenants of the thyroglossal duct that persist called? Where can it usually be found?

A

thyroglossal duct cyst; at its original opening - the foramen cecum of the tongue.

45
Q

What happens as the thyroid descends within the neck?

A

it picks up the superior and inferior parathyroid glands, as well as the parafollicular cells of the ultimobranchial body

46
Q

The ___ arch is the largest and is involved, along with the frontonasal prominence, in the development of the face.

A

mandibular

47
Q

Where is the maxilla derived from?

A

a small maxillary prominence extending cranioventrally from the much larger mandibular prominence

48
Q

What cartilage of the first arch provides a template for subsequent development of the mandible?

A

Meckel’s cartilage

49
Q

What is formed by Meckel’s cartilage?

A
  1. portions of malleus and incus

2. sphenomandibular ligament

50
Q

What is formed when the musculature of the mandibular arch subdivides and migrates?

A

the muscles of mastication (mylohyoid, anterior belly of digastric, tensor tympani, and tensor veli palatini) - all of which are innervated by the mandibular division of the trigeminal nerve (CN V).

51
Q

What is formed by the cartilage of the hyoid arch (Reichert’s cartilage)?

A

most of the stapes
styloid process of the temporal bone
stylohyoid ligament
lesser horn and cranial part of the body of the hyoid bone

52
Q

What are the muscles that are derived from pharyngeal arch 2?

A

stapedius, the stylohyoid, POSTerior belly of digastric and the muscles of facial expression - all of which are innervated by CN VII.

53
Q

What does the cartilage o fthe 3rd pharyngeal arch form?

A

greater horn and caudal body of hyoid

54
Q

What does the mesenchyme of the 3rd pharyngeal arch form?

A

stylopharyngeus muscle (the only muscle innervated by glossopharyngeal nerve (CN IX)

55
Q

Cartilage from arches 4 and 6 form what structures?

A

laryngeal cartilages (thryoid and cricoid) and may contribute to superior tracheal rings

56
Q

T/F: Muscles from arches 4 and 6 are of the palate, pharynx and larynx and receive their motor innervation from the glosspharyngeal nerve.

A

FALSE; Muscles from arches 4 and 6 are of the palate, pharynx and larynx and receive their motor innervation from the VAGUS nerve.

57
Q

The primitive mouth, or ___, is separated from the cranial foregut by the ___ membrane.

A

stomodeum; oropharyngeal

58
Q

When does the development of the oropharyngeal membrane rupture to establish communication between the digestive tract adn the amniotic cavity?

A

about 24 days

59
Q

T/F: The face develops from 5 facial primorida which form around the stomodeum.

A

TRUE

60
Q

A single ___ ___ forms the cranial boundrary of the stomodeum.

A

frontal prominence

61
Q

Paired __ prominences of the first pharyngeal arch forms its lateral boundaries. Paired __ prominences of the first arch form its caudal boundary.

A

maxillary; mandibular

62
Q

How are the lower jaw and lips formed?

A

midline merging of the paired mandibular prominences and are the first parts of the face to become definitively established.

63
Q

The frontonasal prominence surrounds the forebrain, which has already sprouted lateral ___ ___ that will form the eyes.

A

optic diverticula

64
Q

What thickens at the inferolateral corners of the frontonasal prominences?

A

nasal placodes

65
Q

Nasal placodes are ___ placodes that appear to invaginate as inverted horseshoe-shaped masses of cells, the ___ and ___ nasal ridges, proliferate around them.

A

ectodermal; medial; lateral

66
Q

What provides for continuity of the upper jaw an dlip and separation of the nasal pits from the stomodeum?

A

fusion of the medial nasal ridges with the maxillary prominences

67
Q

What forms the philtrum of the upper lip, tip of the nose, and the primary palate of the upper jaw (where upper incisor teeth will form)?

A

the fused medial nasal ridges and frontonasal prominence

68
Q

How is the nasolacrimal duct formed?

A

The lateral nasal ridge and maxillary prominence are initially separated by a deep furrow. AS the lateral nasal ridge and maxillary prominence fuse, the epithelium in the floor of the groove between them forms a solid core that separates from the surface and comes to lie deep to the remnants of the groove. Eventually, this rod canalizes to form the nasolacrimal duct.

69
Q

The palate develops from both the ___ palate, formed by the midline merging of the medial nasal prominences, and the ___ palate, which develops from two internal projections of the maxillary prominences, the ___ ___ ___.

A

primary; secondary; vertical palatine shelves

70
Q

As the jaws continue to develop and grow, the ___ moves inferiorly and the lateral palatine processes elevate into a horizontal position. Once elevated the ___ ___ ___ grow toward one another and fuse.

A

tongue; horizontal palatine shelves - they also fuse with the primary palate anteriorly and the nasal septum superiorly.

71
Q

Loss of ___ ___ (Shh) inhibits the upper jaw growht and leads to ___ (mediolateral narrowing of the frontonasla process) and cleft lip/palate.

A

sonic hedgehog; hypotelorism

72
Q

Overexpression of Shh in the facial primoridal results in ___ (a mediolateral widening of the frontonasal process and a widening between the eyes).

A

hypertelorism

73
Q

What happens when excess Shh is produced?

A

duplication of midfacial structures

74
Q

Tongue development begins when a median elevation, the median tongue bud or ___ ___, becomes visible in the floor of the first pharyngeal arch, just rostral to the ___ ___.

A

tuberculum impar; foramen cecum

75
Q

Two ___ tongue buds rapidly increase in size and merge with one another and overgrow the median bud. They then form the ____ (anterior 1/3rd or anterior 2/3rds) or oral part of the tongue.

A

distal; anterior 2/3rds

76
Q

What is the plane of fusion of the distal buds in the adult?

A

median sulcus of the tongue

77
Q

As a derivative of the ___ pharyngeal arch, the mucosa of the oral part of the tongue received its general somatic afferent innervation from what nerve?

A

first; trigeminal nerve (CN V)

78
Q

Special visceral afferent (taste) innervation of the oral tongue is provided by which nerve?

A

facial n (CN VII)

79
Q

The posterior third of the tongue (pharyngeal part) and the root of the tongue are initially indicated by the ___ (or ___ ___), an elevation of the floors of the third arch and most cranial aspect of the fourth arch.

A

copula; hypobranchial eminence

80
Q

What is the line of fusion of the anterior and posterior parts of the tongue that is indicated by a v-shaped groove called?

A

terminal sulcus

81
Q

The mucosa of the pharyngeal tongue receives its GSA and SVA innervation from the ___ nerve. The root of the tongue receives its GSA and SVA innervation from the ___ nerve.

A

glossopharyngeal; vagus

82
Q

Most of the musculature of the tongue is derived from myoblasts that migrate from the ___ of the ___ ___.

A

myotomes; occipital somites.

83
Q

The ___ nerve accompanies the myoblasts during their migration and innervates the tongue muscles once they have formed.

A

hypoglossal

84
Q

What bones of the skull are derived from pharyngeal arch cartilages?

A
  1. middle ear ossicles
  2. styloid process
  3. mandible
  4. portion of maxilla
  5. hyoid
85
Q

T/F: The bones of the skull not derived from pharyngeal arch cartilages arise only through endochondral ossification.

A

FALSE; The bones of the skull not derived from pharyngeal arch cartilages arise o through endochondral and intramembranous ossification.

86
Q

What portion of bones form by endochondral ossification? How are these elements derived?

A

basicranium; a series of cartilages that form inferior to the developing brain, around the anterior tip of the notochord.

87
Q

With the exception of the occipital portion of the basicranium, which is derived from the ___ of the cranial-most four somites (occipital somites __-__), the cells that form the ___ are of neural crest origin.

A

sclerotomes; 1-4; chondrocranium

88
Q

T/F: All remaining bones of the skull are of intramembranous origin. All but the parietals, squamous protions of the occipital and temporal bones, and mastoid and tympanic portions of the temporals are or neural crest origin.

A

TRUE.

89
Q

Ossification of the skull bones begin at definable locations called what?

A

centers of ossification

90
Q

During development, the growing ossification centers coalesce to form recognizable bones. In the mandible, at its ___ ___ (the condyle), a cartilage develops instead of bone.

A

cranial articulation

91
Q

The ___ carilage, which forms intramembranously and is therefore distinct from the ___ cartilage of the basicranium, will serve as a site of mandibular growth until it too ossifies ___.

A

secondary; primary; endochondrally

92
Q

Why is complete ossification of the calvarial bones delayed until after birth?

A

large size of the human brain

93
Q

The calvarial bones of the newborn infant are separated from one another by large areas of unossified membrane called ___.

A

fontanelles

94
Q

What is the purpose of the presence of fontanelles?

A

to allow the bones to override one another as the baby passes through the birth canal. The shape of the calvarium returns to normal shortly after birth.

95
Q

Where is the anterior fontanelle located?

A

at the junction of the sagittal, coronal and frontal sutures

96
Q

The ___ fontanelle is triangular and is bounded by the parietal bones anteriorly and the occipital bones posteriorly.

A

posterior

97
Q

T/F: Newborn crania display one sphenoidal (anterolateral) and one mastoid (posterolateral) fontanelles.

A

FALSE; Newborn crania display TWO sphenoidal (anterolateral) and TWO mastoid (posterolateral) fontanelles.

98
Q

How are individual bones separated from one another in the skull?

A

sutures

99
Q

Sutures are fibrous joints that allow for very limited movements. What is the function of sutures?

A

to allow for expansion of the growing brain, oculus and extraocular tissues, nasal epithelium and oral cavity. In addition, sutures maintain populations of osteoblasts to allow for sites of bone and cranial growth.

100
Q

T/F: As the soft tissues of the skull mature, sutural growth ceases and the sutures eventually fuse. In some genetic disorders, sutures of the calvarium fuse prematurely.

A

TRUE.

101
Q

___ usually results in cranial deformities since the skull must adjust to this loss of growth potential by exaggerating growth at alternative locations.

A

Craniosynostosis

Anatomy PEDO (1 decks)

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