Embryology of Face, Palate and Nasal Cavity

Question 1

pharyngeal apparatus

Answer 1

..

Question 2

where are the ventral facial features derived from?

Answer 2

pharyngeal arch 1 and 2

Question 3

what ventral facial features are derived from pharyngeal arch 1?

Answer 3

maxilla, mandible, zygomatic and temporal (squamous part) bones
muscles of mastication

Question 4

what ventral facial features are derived from pharyngeal arch 2?

Answer 4

muscles of facial expression

Question 5

where do upper and mid-facial structures derive from?

Answer 5

proliferating mesenchyme ventral to developing brain

Question 6

what 5 swellings are present at week 4 which develop into the face?

Answer 6

frontonasal prominence (with nasal placodes)
2 maxillary prominence (one on each side)
2 mandibular prominences (one on each side)

Question 7

facial development occurs between which weeks?

Answer 7

4-10

Question 8

what is the stomedeum?

Answer 8

primitive oral cavity which the 5 swellings at week 4 surround

Question 9

what forms the nasal placodes?

Answer 9

ectodermal thickenings on the frontonasal prominence

Question 10

what do the nasal placodes become?

Answer 10

nostrils

Question 11

what additional swellings arise in week 5 and where do they occur?

Answer 11

2 medial nasal swellings
2 lateral nasal swellings
develop on the frontonasal prominence on the medial and lateral borders of the nasal placodes

Question 12

the nasal placodes go by another name in week 5, what is this?

Answer 12

nasal pit

Question 13

facial development in week 6?

Answer 13

slit opens slightly
nasal pit gets deeper
frontonasal prominence gets rounder
medial nasal prominences move towards each other

Question 14

what happens in week 7?

Answer 14

medial nasal prominences join to form the intermaxillary segment
palate forms
eyes move around to the front of the face
nasolacrimal groove forms (between medial corner of eye to inferior meatus)

Question 15

what does the nasolacrimal groove become?

Answer 15

nasolacrimal duct

Question 16

where does the nasolacrimal groove lie between?

Answer 16

maxillary prominence and lateral nasal prominence

Question 17

what does the nasolacrimal groove do?

Answer 17

solid epithelial cord in floor of groove
cord detaches from the ectoderm
canalization forms the nasolacrimal duct

Question 18

what are the components of the upper lip?

Answer 18

2 medial nasal prominences

2 maxillary prominences

Question 19

what forms the lower lip?

Answer 19

mandibular prominences

Question 20

what are the components of the nose?

Answer 20

frontonasal prominence (bridge and nasal septum)
medial nasal prominences (crest and tip)
lateral nasal prominences (alae (sides))

Question 21

hoe does the primary palate form and when?

Answer 21

fusion of medial nasal prominences - gives the intermaxillary segment
occurs in week 7

Question 22

what are the 3 components of the intermaxillary segment and what does each apart form?

Answer 22

labial portion = philtrum of upper lip
upper jaw component = carries 4 incisors
palatal component = forms primary palate

Question 23

describe palate at 10 weeks?

Answer 23

the primary and secondary palates fuse to create a single hard palate
- point of fusion = incisive foramen
palatal shelves fuse at the median palatine suture
soft palate and uvula extend off the posterior hard palate

Question 24

what happens to nasal cavities in week 5?

Answer 24

nasal pits deepen and penetrate into the underlying mesenchyme with forward growth of frontonasal prominence

Question 25

what happens in the nasal cavity in week 6?

Answer 25

as the intermaxillary segment forms, it is connected by a nasal fin
nasal fin vacuolizes and thins, this opens the developing nasal sac

Question 26

what is the nasal fin called in week 7?

Answer 26

oronasal membrane

Question 27

what happens in the nasal cavity in week 7?

Answer 27

oronasal membrane disappears allowing the nasal cavities to communicate with oral cavity via primitive choanae
definite choanae open at junction of nasal cavity with pharynx due to formation of secondary palate

Question 28

primitive vs definitive choanae?

Answer 28

primitive = between oral cavity and nasal cavity
definitive = between nasal cavity and nasopharynx

Question 29

how does the secondary palate form?

Answer 29

right and left palateal shelves develop parallel to the tongue
fused in the central region initially, then expand anteriorly and posteriorly
mandibular development facilitates clearance of the tongue

Question 30

when does development of the secondary palate occur?

Answer 30

7th - 10th week

Question 31

why is cleft palate more common in females?

Answer 31

palate development delayed by around 1 week in females

Question 32

in which gender is cleft lip more common?

Answer 32

males