9. Development of nose and face (embryology)

Question 1

what does the face develop from?

Answer 1

most cranial part of neural tube (primitive gut tube)

Question 2

what do the pharyngeal arches become?

Answer 2

the embryonic head and neck:
brain
CVS - heart and great vessels
special sensory organs e.g. eyes

Question 3

what drives the development of the face?

Answer 3

expansion of cranial neural (gut) tube
appearance of complex tissue associated with outflow of developing heart
development of sense organs
need to separate resp tract from GI tract

Question 4

what does each pharyngeal arch contain?

Answer 4

1. artery (aortic arch artery), vein, cranial nerve
   ectoderm covering
   mesenchyme filling
   endodermal lining

Question 5

how are pharyngeal arches arranged?

Answer 5

around aortic arch vessels

Question 6

what is the neural crest?

Answer 6

a specialised population of cells that originates within the neuroectoderm
(ectoderm classification)

Question 7

what is neuroectoderm?

Answer 7

tissue that gives rise to CNS, fold to form neural tube

migrate around body before folding into neural tube to develop into complex nervous system

Question 8

where does the neural crest stem from?

Answer 8

cells of lateral border of neuroectoderm

Question 9

what happens to neural crest cells?

Answer 9

become displaced and enter the Mesoderm (outer to middle)

MIGRATE and contribute to a variety of H+N structures

Question 10

what are the major features of the face?

Answer 10

palpebral fissures (opening of eyes)
oral fissure
nares
philtrum (groove of upper lip)

Question 11

what does the facial skeleton develop from?

Answer 11

neural crest of 1st pharyngeal arch

Question 12

what do muscles of mastication derive from?

Answer 12

mesoderm of 1st pharyngeal arch

Question 13

what do muscles of facial expression develop from?

Answer 13

mesoderm of 2nd pharyngeal arch

Question 14

how does the facial primordia develop?

Answer 14

from 1st pharyngeal arch
frontonasal prominence (FNP)

Question 15

how does the frontonasal prominence (FNP) develop?

Answer 15

surrounds ventro-lateral part of the forebrain

Question 16

what does the frontonasal prominence (FNP) become?

Answer 16

primordia of eyes

Question 17

what is significant about 1st pharyngeal arch?

Answer 17

largest of arches

has 2 zones of prominence (SAME arch)

Question 18

what do the 2 zones of the 1st pharyngeal arch develop into?

Answer 18

maxillary prominence

mandibular prominence

Question 19

what does the nose develop from?

Answer 19

nasal placode

thickening of ectoderm

Question 20

what is contained within the face?

Answer 20

1. stomatodeum
2. frontonasal prominence
3. maxillary + mandibular prominence (1st pharyngeal arch)

Question 21

what is the stomatodeum?

Answer 21

buccopharyngeal membrane (within centre of stomatodeum)
small depression in the head region
(mesoderm - avascular membrane will rupture, giving opening to oral orifice)

Question 22

what does the frontonasal prominence give rise to?

Answer 22

forehead
bridge of nose
nose
philtrum
(a letter T)

Question 23

what does the maxillary prominence give rise to?

Answer 23

cheeks
lateral upper lip
lateral upper jaw
(like innervation of superior alveolar nerve from maxillary V2)

Question 24

what does the mandibular prominence give rise to (external features of the face)?

Answer 24

lower lip and jaw

inferior alveolar nerve

Question 25

where do nasal placodes appear?

Answer 25

frontonasal prominence (thickened growth of ectoderm - outer)
then sinks to become nasal pit (within FNP)

Question 26

what forms either side of nasal pit?

Answer 26

medial and lateral nasal prominences

Question 27

where do maxillary prominences grow?

Answer 27

medially, pushing both nasal prominences closer together in the midline (ready to fuse)

Question 28

what do maxillary prominences fuse with?

Answer 28

medial nasal prominences

Question 29

where do medial nasal prominences fuse?

Answer 29

in the midline

Question 30

what does fusion of medial nasal prominences create?

Answer 30

the intermaxillary segment

Question 31

what does the intermaxillary segment from fusion of medial nasal prominences give rise to?

Answer 31

1. labial component: philtrum
2. upper jaw: 4 incisors
3. palate: primary palate

Question 32

what is the main part of definitive palate?

Answer 32

secondary palate

Question 33

what is definitive palate derived from?

Answer 33

palatal shelves of maxillary prominences

Question 34

initially, what separates nasal pit and oral cavity?

Answer 34

oronasal membrane

Question 35

what happens to the oronasal membrane?

Answer 35

degenerates
so nasal cavity and oral cavity are continuous
(only separated by primary palate near the orifice)

Question 36

how does the nasal cavity and oral cavity then separate?

Answer 36

the secondary palate develops from the primary palate (as an extension, until around the pharynx)

Question 37

what does the maxillary prominence give rise to?

Answer 37

2 palatal shelves (palatine)
which grow vertically downwards into the oral cavity - either side of the developing tongue
(tongue isn’t functioning yet, oral cavity v small)

Question 38

what has to happen after the 2 palatal shelves grow down vertically either side of developing tongue into the small oral cavity?

Answer 38

the mandible grows large enough to allow the tongue to ‘drop’ (into the oral cavity properly)

Question 39

what happens after the tongue has dropped?

Answer 39

the palatal shelves then grow towards each other and fuse in the midline (forming the continuous palate)

Question 40

what happens after the palatal shelves have fused with each other?

Answer 40

the nasal septum develops as a midline down-growth and ultimately fuses with palatal shelves
(nasal cavity and oral cavity both drain to middle meatus)

Question 41

what is the intermaxillary segment?

Answer 41

medial nasal prominences

Question 42

what does the intermaxillary segment (medial nasal prominences) fuse with?

Answer 42

maxillary process (prominences)

Question 43

what does the intermaxillary esgment (medial nasal prominences) give rise to?

Answer 43

philtrum

primary palate

Question 44

what does the maxillary process give rise to?

Answer 44

fused palatal (palatine) shelves