13) Development of Face and Nose

Question 1

What are neural crest cells?

Answer 1

Specialised population of cells originating within neuroectoderm. Becomes displaced and enters mesoderm

Question 2

What are the major facial features?

Answer 2

Palpebral fissures (between eyelids), oral fissure, nares, philtrum

Question 3

What does the facial skeleton form from?

Answer 3

Neural crest of 1st pharyngeal arch

Question 4

What do the muscles of mastication form from?

Answer 4

Mesoderm of 1st pharyngeal arch

Question 5

What do the muscles of facial expression form from?

Answer 5

Mesoderm of 2nd pharyngeal arch

Question 6

What are the 5 building blocks (prominences) of the embryological face?

Answer 6

Frontonasal prominence
2 maxillary prominences
2 mandibular prominences

Question 7

What is the stomatodeum?

What does it go on to form?

Answer 7

Depression of ectoderm on ventral head

Forms buccopharyngeal membrane -> mouth

Question 8

What parts of the face are derived from the frontonasal prominence?

Answer 8

Forehead
Bridge of nose, nose and philtrum
Upper eyelids

Question 9

What parts of the face are derived from the maxillary prominence?

Answer 9

Cheeks
Lateral upper lip
Lateral upper jaw

Question 10

What parts of the face are derived from the mandibular prominence?

Answer 10

Lower lip and jaw

Question 11

What is the first evidence of nose formation?

Answer 11

Nasal placodes appear on FNP

Question 12

What happens to the nasal placodes?

Answer 12

Invaginate and form deep pits, entrance to pit = future nostril

Question 13

How does the nose form in the midline?

Answer 13

Maxillary prominences grow medially pushing nasal prominences (either side of pits) to midline where medial nasal prominences fuse with each other and maxillary prominences

Question 14

What does fusion of the medial nasal prominences create?

Answer 14

Intermaxillary segment consisting of philtrum, upper jaw and primary palate

Question 15

What gives rise to the palatal shelves?

Answer 15

Maxillary prominences

Question 16

How do the palatal shelves fuse in the midline and what does this create?

Answer 16

When mandible has grown enough to allow tongue to drop out of the way, palatal shelves can fuse to form secondary palate

Question 17

What is the pathophysiology behind cleft lip?

Answer 17

Failure of fusion of medial nasal prominence and maxillary prominence

Question 18

What are the consequences of cleft lip on the new-born?

Answer 18

Difficulty suckling and with speech

Question 19

Where are the eyes derived from?

Answer 19

Forebrain

Question 20

What is the lens derived from?

Answer 20

Optic placode

Question 21

Where are the eyes originally and how do they end up on the front of the face?

Answer 21

Originally on side of head but move as facial prominences grow

Question 22

Where does the external auditory meatus derive from?

Answer 22

1st pharyngeal cleft

Question 23

Where do the auricles derive from?

Answer 23

Proliferation of 1st and 2nd pharyngeal arches

Question 24

How do the external ears ascend from neck?

Answer 24

Growth of mandible

Question 25

Where does the inner ear derive from?

Answer 25

Otic placodes

Question 26

What effects does alcohol have on the fetus?

Answer 26

Effects on neural crest migration and development of brain

Question 27

What are the signs and symptoms of fetal alcohol syndrome?

Answer 27

Small head, short nose and flat midface