Development Of The Nose And Face

Question 1

Where do neural crest cells originate from and where do they migrate to?

Answer 1

From within the neuroectoderm which has differentiated from ectoderm under the influence of the neural tube.

Question 2

How is the neural crest formed?

Answer 2

Cells of the lateral border of the neuroectoderm become displaced and enter the mesoderm. They migrate and contribute to a variety of head and neck structures which happens as the neural tube fuses this is how the neural crest develops.

Question 3

What are the major features of the face?

Answer 3

Palpebral fissures
Oral fissures
Nares
Philtum

Question 4

Where is the facial skeleton derived from?

Answer 4

Neural crest of the first pharyngeal arch

Question 5

Where are the muscles of mastication derived from?

Answer 5

Mesoderm of the first pharyngeal arch

Question 6

Where are the muscles of facial expression derived from?

Answer 6

Second pharyngeal arch

Question 7

Where are the facial primordia derived from?

Answer 7

The first pharyngeal arch

Question 8

What does the frontonasal prominence surround and what is found on it?

Answer 8

The ventrolateral part of the forebrain

Primordia of the eyes

Question 9

How does the nose develop in the first stages?

Answer 9

Nasal placodes appear on FNP which sink to become nasal pits
Medial and lateral prominences form on either side of the pits
Rupturing of the buccopharyngeal membrane causes opening into cranial parts of the primitive gut tube

Question 10

How does the nose fuse?

Answer 10

Maxillary prominences grow medially, pushing the nasal prominences closer together in the midline.
Maxillary prominences fuse with the medial nasal prominences and medial prominences fuse in the midline

Question 11

What does fusion of the medial nasal prominences create?

Answer 11

The intermaxillary segment

Question 12

What are the components of the intermaxillary segment?

Answer 12

Labial component - philtrum
Upper jaw - 4 incisors
Palate - primary palate

Question 13

What makes up the main part of the definitive palate?

Answer 13

The secondary palate

Question 14

What is the secondary palate derived from?

Answer 14

Palatal shelves which are derived from the maxillary prominences

Question 15

What separates the nose from the mouth?

Answer 15

The secondary palate

Question 16

How does the secondary palate develop?

Answer 16

The maxillary prominence gives rise to two palatal shelves
They grow vertically downwards into the oral cavity on each side of the developing tongue
The mandible grows large enough to expand the oral cavity and allow the tongue to drop
Palatal shelves then grow towards eachother and fuse in the midline on roof of mouth

Question 17

How does the nasal septum develop?

Answer 17

As a midline down-growth to ultimately fuse with the palatal shelves

Question 18

What is a lateral cleft lip?

Answer 18

Failure of fusion of the medial nasal prominence and maxillary prominence

Question 19

What is a cleft lip and cleft palate?

Answer 19

Combined with failure of the palatal shelves to meet in the midline

Question 20

What happens to the frontonasal prominence?

Answer 20

Becomes the forehead, bridge of nose, medial and lateral nasal prominences

Question 21

What happens to the medial nasal prominence?

Answer 21

Philtrum
Primary palate
Mid upper jaw

Question 22

What does the lateral nasal prominence become?

Answer 22

Sides of the nose

Question 23

What does the maxillary prominence become?

Answer 23

Cheeks
Lateral upper lip
Secondary palate
Lateral upper jaw

Question 24

What does the mandibular prominence become?

Answer 24

Lower jaw and lip

Question 25

In which week does development of the eyes begin?

Answer 25

Fourth week

Question 26

How do the eyes develop?

Answer 26

Outpocketings of the forebrain grow out to make contact with overlying ectoderm
Optic placodes will develop into the lens of the eye
Optic vesicles grow out towards the surface to make contact with the lens placodes
Lens placode invaginates and pinches off

Question 27

Where is the retina derived from?

Answer 27

Diencephalon (forebrain)

Question 28

What is the positioning of the eye primordia?

Answer 28

Positioned on the side of the head

As facial prominences grow, the eyes move to the front of the face giving binocular vision

Question 29

Where does the external auditory meatus develop from?

Answer 29

First pharyngeal cleft

Question 30

What do the auricles of the ear develop from?

Answer 30

First and second pharyngeal arches surrounding the meatus

Question 31

What is the positioning of the external ears?

Answer 31

Develop initially in the neck

As mandible grows, the ears ascend to the side of the head to lie in line with the eyes

Question 32

What are all common chromosomal abnormalities associated with?

Answer 32

External ear anomalies

Question 33

Where is the inner ear derived from?

Answer 33

Otic placodes

Question 34

How does the inner ear develop?

Answer 34

Otic placodes invaginate into the auditory vesicles

Have a membranous labyrinth made up of a cochlea and semi-lunar canal system

Question 35

What is fetal alcohol syndrome?

Answer 35

Neural crest cell migration and development of the brain are known to be extremely sensitive to alcohol

Question 36

What is the incidence of fetal alcohol syndrome and alcohol-related neuro-developmental disorder (ARND)?

Answer 36

1/100 births

Question 37

Which placodes does vision, smell, hearing and balance come from?

Answer 37

Vision - optic placode
Smell - nasal placode
Hearing and balance - otic placode

Question 38

What is development of the face driven by?

Answer 38

Expansion of the cranial neural tube forming a large frontonasal prominence