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Flashcards in Head and Neck development Deck (78):
1

Folding of embryo forms these two structures

primitive mouth (stomodeum) and forgut

2

What forms on either side in the floor of the pharynx during formation of foregut and stomodeum

Five pairs of pharyngeal arches

3

What do the pharyngeal arches consist of?

Mesodermal core covered by ectoderm, and lined by pharyngeal endoderm (EXCEPT the first)

4

Each arch appears as a swelling containing a cartilaginous rod form by?

Neural crest cells

5

Sequential swellings are separated by constrictions caused by these invaginations of the ectoderm. How many?

Pharyngeal clefts, 4

6

Evaginations of the endoderm. How many?

Pharyngeal pouches, 4

7

The narrow, constricted areas between clefts and pouches.

Pharyngeal membranes

8

In more primitive vertebrates, the membranes between clefts and pouches function for/form?

Gill slits or functioning gills. This doesn't occur in humans, and are no longer necessary for breathing and filter feeding. Freed for other uses.

9

Muscle precursors derive from?

Paraxial somitomeres (recall paraxial mesoderm forms somites which go on to form myotome, dermatome, and sclerotome)

10

Arch 1 correlates with which CN?

CN V (Trigeminal, both)

11

Arch 2 correlates with which CN?

CN VII (Facial, both)

12

Arch 3 correlates with which CN?

CN IX (glossopharyngeal, both)

13

Arch 4 and 6 correlate with which CN?

CN X (Vagus, both)

14

Each cartilaginous rod that has migrated into the arch from rhombomeres make up these 4 important structures:

embryonic hindbrain, muscle precursors, aortic arch artery, and associated nerve

15

Transiently divided segment of the developing neural tube, within the hindbrain region in the area that will eventually become the rhombencephalon

Rhombomere, appear as a series of constricted swellings in the neural tube

16

What does the primitive mouth area is lined by what derived epithelium?

Ectodermal

17

The epithelial layer of the pharynx is derived from?

Endoderm

18

In humans the first arch cartilages persist as the Palatopterygoquadrate bars and Meckle's cartilage (from maxilla and mandible process, respectively). What do their upper ends become?

The incus and malleus bones of the middle ear

19

Membrane bone from the neural crest mesenchyme develops and surrounded the remaining first arch cartilage to form these 4 bones:

Maxillary, Mandibular, zygomatic (cheek bones), and squamous temporal bones.

20

The first arch somitomeric mesoderm yields these 5 muscles:

1. Muscles of mastication
2. Tensor tympani
3. Tensor veli palatini
4. Anterior belly of digastric
5. Mylohyloid

21

Second arch cartilage gives rise to these 3 bones:

1. lesser cornu and upper rim of hyoid bone
2. third ossicle of middle ear (stapes)
3. styloid process

22

Muscles associated with second arch (4)

All muscles of facial expression including:
1. platysma
2. stylohyoid
3. stapedius
4. posterior belly of digastric

23

Third arch cartilage gives rise to this bone:

Greater cornu and lower rim of hyoid bone

24

The only muscle developed from third arch

Stylopharyngeous (innervated by CN IX)

25

What does the artery of the third arch give rise to?

Common carotid and base (first part) of the internal carotid

26

What do the fourth and sixth arches develop into? (1 with 5 parts)

laryngeal cartilage:
1. thyroid
2. cricothyroid
3. arytenoid
4. coniculate
5. cuneiform

27

Muscles derived from the fourth arch mesoderm (3)

1. Pharyngeal constrictors
2. Cricothyroid
3. levator veli palatine + other palatal muscles

28

Muscles derived from the sixth arch (2)

1. intrinsic muscles of larynx
2. striated muscle of esophagus

29

Primary nerve [of vagus nerve] of the fourth arch derivative

superior laryngeal branch of vagus nerve

30

Innervation of the sixty arch muscles are from which nerve?

Recurrent laryngeal branch of the vagus nerve

31

The vagus nerve also contributes to innervation of the soft palate and pharyngeal constrictors through its contributions to what?

The pharyngeal plexus

32

What happens to the fifth arch?

In humans, it either never forms or is rudimentary and disappears

33

The first pharyngeal pouch expands to form these two structures

1. Tubotympanic recess- gives rise to tympanic cavity of the middle ear
2. Pharyngotympanic tube (eustachian tube/auditory tube) connecting the middle ear cavity and nasal pharynx

34

What does the pharyngeal membrane between the first clefts and pouches form?

The tympanic membrane (eardrum)

35

What does the second pouch form?

The palatine tonsils

36

The third pouch gives rise to what two regions?

A solid dorsal region and a hollow elongated ventral region

37

Where does the thymus originate from?

Ventral regions of the third pouches

38

Solid cords that break their connection with the pharynx migrate bilaterally and eventually form what?

The thorax, fuse into a single gland

39

Where does the inferior parathyroid gland originate from?

The dorsal region of the third pouch

40

Which pouch in addition to the third pouch has dorsal and ventral regions?

The fourth pouches

41

What two important structures does the fourth pouch form?

1. Superior parathyroid (dorsal)
2. Ultimobranchial body (ventral)

42

Of neural crest origin, these cells give rise to the calcitonin secreting C cells of the parafollicular thyroid

Ultimobranchial body (small organ found in the neck region)

43

The last 3 pharyngeal clefts usually disappear and become covered by the second arch, however the first cleft becomes these two structures:

1. external acoustic meatus (ear canal)
2. External layer of tympanic membrane

44

This develops by proliferation of cells in the floor of the pharynx between the first and second pouches

Thyroid gland

45

The most common congenital malformation of the head and neck

Unilateral cleft lip (failure of one of maxillary prominence to fuse with medial nasal prominence of same side)

46

Cleft palate, a defect distinct from cleft lip, is usually classified as anterior or posterior, distinguishable by their relationship to what?

The incisive foramen

47

First arch syndrome, the lumping together of first arch, is usually a result from failure of what?

Failure of neural crest cells to migrate into the arch

48

DiGeorge Syndrome

complex constellation of anomalies caused by deletion of chromosome 22 (first arch anomalies, immunological deficiencies with thymus, deficiencies of thyroid and parathyroid glands, cardiovascular anomalies)

49

Common denominator for DiGeorge syndrome

Impaired neural crest migration into the third and fourth arches

50

The hard palate is formed in how many stages?

2

51

This segment contributes to the upper lip (philtrum) and a jaw component carrying the incisor teeth, forming the triangular primary palate

Intermaxillary segment (has deep palatal compartments)

52

What forms the secondary palate?

Formed by paired outgrowth of the maxilla

53

Ventrally, what undergoes endochondrial ossification to form the hard palate?

Mesenchymal condensations

54

Posteriorly, what condenses to form the soft palate?

Myogenic mesenchyme

55

Expansion of the face continues after birth by development and expansion of

paransal sinuses

56

Paransal sinues (air filled spaces) develop as diverticular of the lateral nasal wall and invade and expand within which 4 bones?

1. Maxillary
2. Ethmoid
3. Sphenoid
4. Frontal

57

Mandibulofacial dysostosis, genetic basis, inherited as autosomal dominant (first arch syndrome)

Treacher Collins

58

The tongue develops from which arch?

1, 3, and 4

59

What forms the intrinsic and extrinsic muscles of the tongue?

migrating occipital somite mesoderm

60

What innervate the muscles in tongue derived from occipital somites?

hypoglossal nerve CN XII

61

The mucosa of the anterior two-thirds of the tongue receives general sensory innervation from which nerve?

CN V

62

The posterior third of the tongue received its innervation for both general and taste from which nerve?

CN IX (glossophyrangeal)

63

A small area on the dorsal most part of the root or pharyngeal part of tongue receives general and taste sensation from?

superior laryngeal branch of CN X (vagus)

64

Taste to the anterior two-thirds is from what nerve?

Chorda tympani branch of CN VII (facial)

65

Most recent evidence is that taste buds form independtly in this, but survive only if what are present?

Form in lingual epithelium, need nerves to survive

66

All "glossus" muscles (muscles of palate) are innervated by CN XII, except for this muscle

Palatoglossus

67

The five facial swellings

An unpaired frontonasal prominence on anterior end of developing embryo, and paired maxillary and mandibular prominences (form from growth and division of the paired first pharyngeal arches)

68

The five prominences form this major facial feature

The nose

69

What forms the bridge of the nose?

The frontonasal prominence

70

Formation of the tongue

Pharyngeal arches 1, 3, and 4

71

The thyroid develops from an invagination of the tongue endoderm between what two structures? Later indicated by what foramen?

Tuberculum impar and copula linguae. Foramen cecum

72

Through where does the thyroid migrate to its porper position?

Thyroglossal duct

73

Unilateral cleft lip can result from these two factors:

-maxillary prominence fails to fuse with medial nasal prominence
-underlying somitomeric mesoderm and neural crest fail to expand, resulting in a "persistent labial groove"

74

What does the intermaxillary segment form?

The philtrum of the lip, the incisors (4), and the primary palate

75

Palatine shelves

outgrowths of maxillary prominences

76

The secondary palate forms from outgrowths of these structures

palatine shelves, maxillary promimences

77

palatine shelves project downward on either side of tongue but later attain a horizontal postition and fuse along the ________ to form the ______

palatine raphe, secondary palate

78

Where do the primary and secondary palates fuse? to form what?

incisive foramen, definitive palate