Development of the Pharyngeal Apparatus

Question 1

What makes up the pharyngeal apparatus?

Answer 1

pharyngeal arches, pouches, grooves, and membranes

Question 2

When do the pharyngeal arches develop?

Answer 2

early in the 4th week

Question 3

What is the first pair of arches known as?

Answer 3

the primordial jaws

Question 4

What initiates the formation of the pharyngeal arches?

Answer 4

NCCs migrate away from the dorsal aspect of the developing neural tube and begin to populate ventral areas in what will be the head and neck

Question 5

Where do cranial neural crest cells migrate from?

Answer 5

forebrain, midbrain, and hindbrain regions in the developing neural tube

Question 6

what are the three main components of the pharyngeal arches?

Answer 6

core, external lining, internal lining

Question 7

what is the core of the pharyngeal arches composed of?

Answer 7

mesoderm and mesenchyme

Question 8

what is the external lining of the pharyngeal arch composed of?

Answer 8

ectoderm

Question 9

what is the internal lining of the pharyngeal arch composed of?

Answer 9

endoderm

Question 10

What is mesenchyme

Answer 10

embryonic CT

Question 11

where does the mesoderm in the core of the pharyngeal arch come from?

Answer 11

it arises from paraxial mesoderm

Question 12

what does the NCC-derived mesenchyme in the pharyngeal arch form?

Answer 12

all connective tissue in the head, including the dermis and smooth muscle

Question 13

what does the paraxial mesoderm in the pharyngeal arch form?

Answer 13

forms PA musculature

Question 14

what does the lateral plate mesoderm in the PA form?

Answer 14

angioblasts that differentiate into endothelium

Question 15

what does prechordal plate mesoderm in the PA form?

Answer 15

extraocular musculature

Question 16

What is the cartilage of the first pharyngeal arch also known as?

Answer 16

Meckle’s cartilage

Question 17

what does the dorsal part of meckle’s cartilage form?

Answer 17

malleus and the incus

Question 18

what does the ventral part of meckle’s cartilage form?

Answer 18

primordium of the mandible (like a place holder)

Question 19

what does the perichondrium of meckle’s cartilage form?

Answer 19

anterior ligament of the malleus and the sphenomandibular ligament

Question 20

what is the cartilage of the 2nd pharyngeal arch also known as?

Answer 20

riechert’s cartilage

Question 21

what does the dorsal part of riechert’s cartilage form?

Answer 21

stapes and styloid process o the temporal bone

Question 22

what does the perichondrium of riechert’s cartilage form?

Answer 22

the styloidhyoid ligament

Question 23

what does the ventral portion of riechert’s cartilage form?

Answer 23

It ossifies to form the lesser cornu/horn of the hyoid bone

Question 24

What does the third pharyngeal arch cartilage form?

Answer 24

it ossifies to form the greater cornu/horn of the hyoid bone

Question 25

what is the body of the hyoid bone formed by?

Answer 25

the hypopharyngeal eminence

Question 26

what does the cartilage of the 4th pharyngeal arch form?

Answer 26

laryngeal cartilages including the epiglottis

Question 27

what does the cartilage of the 6th pharyngeal arch form?

Answer 27

laryngeal cartilages

Question 28

Most muscular components of the face arise from what?

Answer 28

paraxial mesoderm

Question 29

the first pharyngeal arch gives rise to what musculature?

Answer 29

muscles of mastication, mylohyoid, anterior belly of the digastric, tensor veli palatini, and tensor tympani

Question 30

the second pharyngeal arch gives rise to what musculature?

Answer 30

stapedius and muscles of facial expression

Question 31

the third pharyngeal arch gives rise to what musculature?

Answer 31

the stylopharyngeus

Question 32

the fourth pharyngeal arch gives rise to what musculature?

Answer 32

cricothyroid and pharyngeal constrictors

Question 33

the sixth pharyngeal arch gives rise to what musculature?

Answer 33

intrinsic muscles of the larynx

Question 34

where do the extraocular muscles arise from?

Answer 34

the prechordal plate

Question 35

where does the tongue musculature arise from?

Answer 35

the occipital myotomes

Question 36

what nerve supplies the first pharyngeal arch?

Answer 36

trigeminal (maxillary and mandibular divisions)

Question 37

what nerve supplies the second pharyngeal arch?

Answer 37

facial

Question 38

what nerve supplies the third pharyngeal arch?

Answer 38

glossopharyngeal

Question 39

what nerve supplies the 4-6th pharyngeal arch?

Answer 39

vagus

Question 40

what are the general signs of a first arch syndrome?

Answer 40

malformation of the eyes, ears, mandible, and palate

Question 41

what causes a first arch syndrome?

Answer 41

insufficient migration of NCC into the 1st arch during the 4th week of development

Question 42

what is another name for treacher-collins syndrome?

Answer 42

mandibulofacial dysostosis

Question 43

what causes treacher-collins syndrome?

Answer 43

mutations in TCOF1 gene

Question 44

what does TCOF1 encode for?

Answer 44

the protein TREACLE, which is involved in ribosome biogenesis

Question 45

what happens if the TREACLE protein is truncated?

Answer 45

there is increased apoptosis of cranial NCCs

Question 46

what is pierre robin sequence associated with?

Answer 46

hypoplasia of the mandible, cleft palate, and defects of the eyes and ears

Question 47

what is the initiating defect of pierre robin sequence?

Answer 47

small mandible (micrognathia)

Question 48

where are pharyngeal grooves located?

Answer 48

externally between pharyngeal arches (covered with ectoderm)

Question 49

where are pharyngeal pouches located?

Answer 49

internally as part of the pharynx (covered with endoderm)

Question 50

what does the first pharyngeal groove form?

Answer 50

the external acoustic meatus

Question 51

where do grooves 2-4 lie?

Answer 51

in the cervical sinus

Question 52

what does the first pharyngeal pouch become?

Answer 52

it expands into the tubotympanic recess, which becomes the tympanic cavity and mastoid antrum

Question 53

the tubotympanic recess will eventually elongate into what?

Answer 53

the pharyngotympanic tube (auditory tube)

Question 54

what forms the tympanic membrane?

Answer 54

the 1st pharyngeal membrane + the intervening mesenchyme

Question 55

what does the second pouch form?

Answer 55

tonsillar sinus

Question 56

what does the endoderm of the second sinus form?

Answer 56

tonsillar epithelium

Question 57

what does mesenchyme from the second pouch form?

Answer 57

lymphoid nodules of palatine tonsil

Question 58

what does the dorsal part of the third pouch become?

Answer 58

inferior parathyroid gland

Question 59

what does the ventral part of the third pouch become?

Answer 59

thymus

Question 60

where does the third pouch migrate to?

Answer 60

caudally (due to growth of brain and cardiac regions)

Question 61

what does the dorsal part of the 4th pouch become?

Answer 61

superior parathyroid gland

Question 62

what does the remainder of the 4th pouch become?

Answer 62

an ultimobranchial body

Question 63

what happens to the ultimobranchial body?

Answer 63

it fuses with the thyroid gland and gives rise to the parafollicular cells

Question 64

how is an external cervical sinus detected?

Answer 64

due to discharge of mucus

Question 65

what is an external cervical sinus commonly associated with?

Answer 65

auricular sinuses

Question 66

when does the thyroid gland (thyroid primordium) develop?

Answer 66

around day 24 of development

Question 67

what does the thyroid primordium form from?

Answer 67

an endodermal thickening in the floor of the primordial pharynx

Question 68

how is the thyroid gland connected to the tongue?

Answer 68

by a narrow tube known as the thyroglossal duct

Question 69

When will the thyroid primordium become its definitive shape/ when will the thyroglossal duct degenerate?

Answer 69

week 7

Question 70

what is mesenchyme derived from?

Answer 70

migratory NCCs

Question 71

What kind of mesoderm is located in the core of the pharyngeal arch?

Answer 71

paraxial mesoderm (largest contributor), lateral plate mesoderm, and prechordal plate mesoderm

Question 72

What is the hypopharyngeal eminence?

Answer 72

a prominence in the floor of the embryonic pharynx (from PA3 and PA4)

Question 73

obstruction of full closure of the palate due to micrognathia leads to what?

Answer 73

bilateral cleft palate

Question 74

what is an external cervical sinus?

Answer 74

failure of the 2nd groove and cervical sinus to obliterate

Question 75

what is an internal cervical sinus?

Answer 75

ingrowth of the 2nd pouch

Question 76

what are remnants of the cervical sinus and/or 2nd groove that get covered with skin?

Answer 76

cervical cysts

Question 77

What does an internal cervical sinus open into?

Answer 77

tonsillar sinus

Question 78

what is it called when the second pouch remains open out to the second groove and then there is leakage of fluid and other substances that pass through the external opening of the skin?

Answer 78

cervical fistula

Question 79

what is it called when the thyroid gland develops but does not descend?

Answer 79

sublingual thyroid gland

Question 80

what is DiGeorge syndrome?

Answer 80

a breakdown of signaling from PA endoderm to NCC

Question 81

what is not formed in digeorge syndrome?

Answer 81

thymus and parathyroid gland