Embryology of the Head and Neck: The Pharyngeal Apparatus

Question 1

What two cell types form the branchial arch mesenchyme?

Answer 1

neural crest cells & head mesoderm

Question 2

What is the fate of the cervical sinus?

Answer 2

It goes away (in normal development)

Question 3

What is DiGeorge Syndrome?

Answer 3

failure of pouches 3 & 4 to form = no thymus or parathyroid glands

Question 4

What is ankyloglossia?

Answer 4

lingual frenulum is too short (“tongue-tied”)

Question 5

What happens to branchial arch 1?

Answer 5

divides and forms maxillary and mandibular prominences

Question 6

What happens to branchial arch 2?

Answer 6

overgrows arches 3 & 4 and the branchial grooves in between -> smooth neck

Question 7

What happens to branchial arches 3 and 4?

Answer 7

become internalized

Question 8

What cell type forms the pharyngeal pouches?

Answer 8

endoderm

Question 9

What cell type forms the branchial grooves?

Answer 9

ectoderm

Question 10

What happens to branchial groove 1 (between arches 1 & 2)?

Answer 10

becomes external acoustic meatus

Question 11

What happens to branchial membrane 1 (between groove 1 & pouch 1)?

Answer 11

tympanic membrane

Question 12

What forms the auricle/pinna of the outer ear?

Answer 12

adjacent parts of arches 1 & 2

Question 13

What abnormalities can occur if the cervical sinus does not disappear?

Answer 13

branchial cyst
branchial fistula
branchial sinus

Question 14

What happens to pouch 1?

Answer 14

forms eustachian tubes as well as forms tympanic cavity (envelops the middle ear bones)

Question 15

What happens to pouch 2?

Answer 15

helps form the palatine tonsil

Question 16

What happens to pouch 3?

Answer 16

swells, forms bulbous end, buds off, migrates down (farther than pouch 4)
THYMUS
INFERIOR PARATHYROID GLANDS

Question 17

What happens to pouch 4?

Answer 17

swells, forms bulbous end, buds off, migrates down (not as far as pouch 3)
SUPERIOR PARATHYROID GLANDS

Question 18

How are the epiglottis, larynx, vocal cords, and tongue buds formed?

Answer 18

Branchial arch mesenchyme migrates under the floor of the pharynx and pushes up swellings.

Question 19

What cell types form the connective tissue of the tongue?

Answer 19

neural crest cells of branchial arch mesenchyme

Question 20

What cell types form the muscles of the tongue?

Answer 20

head mesoderm of branchial arch mesenchyme

Question 21

What do the branchial arch arteries help form?

Answer 21

aortic arch arteries

Question 22

What does the branchial arch cartilage form?

Answer 22

viscerocranium

Question 23

What are the first 5 prominences of the primitive face?

Answer 23

frontonasal prominence
2 maxillary prominences
2 mandibular prominences

Question 24

What are the 4 additional prominences that form the primitive face?

Answer 24

2 medial nasal prominences

2 lateral nasal prominences

Question 25

How is the intermaxillary segment formed?

Answer 25

fusion of the medial nasal prominences

Question 26

What forms the lower lip and lower jaw?

Answer 26

mandibular prominences

Question 27

What forms most of the upper lip, upper jaw, and secondary palate?

Answer 27

maxillary prominences

Question 28

What forms the intermaxillary segment of the upper lip/jaw as well as the philtrum of the lip and the primary palate?

Answer 28

medial nasal prominences

Question 29

What forms the sides of the nose?

Answer 29

lateral nasal prominences

Question 30

What forms the forehead and the superior part of the nose?

Answer 30

frontonasal prominences

Question 31

What can happen if the maxillary prominences don’t migrate or fuse correctly?

Answer 31

cleft lip or cleft palate

Question 32

What forms the primitive nasal cavity?

Answer 32

internal extension of the nasal pits

Question 33

What forms the primary palate?

Answer 33

extensions from the intermaxillary segment (which is formed from the medial nasal prominences)

Question 34

What forms the secondary palate?

Answer 34

extensions from the maxillary prominences

Question 35

When do the paranasal sinuses form and what do they allow you to do?

Answer 35

form mostly after birth and allow you to do throat singing

Question 36

What is located in the primary palate?

Answer 36

incisor teeth

Question 37

What normally happens with the primary and secondary palate?

Answer 37

they fuse to form the palate

Question 38

What can happen if the primary and secondary palates don’t fuse correctly?

Answer 38

cleft palate or cleft palate with cleft lip

Question 39

What structures does the first arch contribute to?

Answer 39

upper and lower jaw
palate
ear
tongue
helps form eye (indirectly)