Session 4 - Development of the Nose, face, and temporal region

Question 1

Where does the neural crest originate?

Answer 1

neuroectoderm

Question 2

Answer 2

Question 3

What is the opening of the mouth known as? What are the creases from side of mouth to nose known as?

Answer 3

Oral fissure – Opening of mouth

Nasolabial folds – Creases from side of mouth to nose

Question 4

What can the 1st PA be broken down into? What does each part develop into?

Answer 4

FNP
Stomatodeum (small depression) - Buccopharyngeal membrane
Maxillary prominence
Mandibular prominence

FNP – forehead, bridge of nose, nose, philtrum
Maxillary – Cheeks, lateral upper lip and lateral upper jaw
Mandibular – Lower lip and jaw

Question 5

Describe the process of development of the face up to the fusion of the medial nasal prominences to create the intermaxillary segment.

Answer 5

1. Nasal placodes appear on frontonasal prominence (shadowed areas of diagram)
2. Then sink to become the nasal pits
3. Medial and lateral nasal prominences form on either side of the pits due to the depression of the nasal pits
4. Buccopharyngeal membrane ruptures
5. Maxillary prominences grow medially, pushing the nasal prominences closer together in the midline
6. Maxillary prominences fuse with the medial nasal prominences
7. Medial nasal prominences then fuse in the midline
8. Fusion of medial nasal prominences creates the intermaxillary segment

Question 6

What does the intermaxillary segment consist of?

Answer 6

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

Question 7

Describe the development of the face after the formation of the intermaxillary segment

Answer 7

1. Secondary palate derived from palatal shelves derived from maxillary prominences – Palatal shelves grow vertically downwards into the oral cavity on each side of the developing tongue
2. The mandible then grows large enough to allow the tongue to ‘drop’ / flatten out.
3. The palatal shelves then grow towards each other and fuse in the midline. Nasal septum develops as a midline down-growth and fuses with palatal shelves

Question 8

What is a lateral cleft lip?

Answer 8

Failure of fusion of medial nasal prominences and maxillary prominence

Question 9

What is a cleft lip and cleft palate? What does a cleft lip cause a problem with?

Answer 9

Failure of fusion of medial nasal prominences and maxillary prominence Combined with failure of palatal shelves to meet in midline

Causes problem with suckling

Question 10

When does the developement of the eyes begin? Describe the development of the eyes.

Answer 10

1. Development begins in 4th week
2. Out-pocketings of the forebrain which grows out to make contact with overlying ectoderm
3. Optic vesicles grow out towards the surface to make contact with the lens placode
4. Lens placode then invaginates and pinches off
5. Optic placode gives rise to lens. Retina derived from Diencephalon (ie forebrain)
6. Growth of facial prominences pushes eyes from side to front of face

Question 11

What does the external auditory auditory meatus develop from??

Answer 11

1st Ph Cleft

Question 12

What does the auricles of the ear develop from?

Answer 12

1st and 2nd Ph arches

Question 13

Describe how the ears end up in the position they are found.

Answer 13

• Ears develop initially in neck
• As mandibles grow the ears ascend to side of the head to lie in line with the eyes
• All common chromosomal abnormalities have associated external ear anomalies

Question 14

What are the features of someone suffering from fetal alcohol syndrome? What is the incidence of FAS?

Answer 14

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