Development of the Face

Question 1

What is the first evidence of the development of the face?

Answer 1

The appearance of the stomadaeum

Question 2

What is the stomadaeum?

Answer 2

A depression in the ectoderm on the ventral aspect of the head

Question 3

What is the stomadauem the site of?

Answer 3

The future mouth

Question 4

How is the stomodeum seperated from the anterior end of the foregut?

Answer 4

By the buccopharyngeal membrane

Question 5

Describe the ectoderm, mesoderm, and endoderm arrangement at the buccopharyngeal membrane?

Answer 5

No mesoderm between ectoderm/endoderm

Question 6

What form around the stomadauem?

Answer 6

Five folds (prominences/processes)

Question 7

What are the prominences/processes that form around the stomadauem?

Answer 7

• Frontonasal prominence
• Maxillary prominences (2)
• Mandibular prominences (2)

Question 8

Where does the frontonsal prominence form?

Answer 8

Superiorly, in the midline

Question 9

What does the frontonasal prominence form?

Answer 9

• Forehead
• Bridge of nose
• Upper eyelids
• Centre of upper lip

Question 10

Where are the maxillary prominences?

Answer 10

Laterally

Question 11

What are the maxillary prominences derived from?

Answer 11

The 1st pharyngeal arch

Question 12

What do the maxillary prominences form?

Answer 12

• Middle third of face
• Upper jaw
• Most of the lip
• Sides of the nose

Question 13

Where are the mandibular prominences?

Answer 13

Inferolaterally

Question 14

What are the mandibular prominences derived from?

Answer 14

The 1st pharyngeal arch

Question 15

What do the mandibular prominences form?

Answer 15

• Lower 1/3 of the face
• Lower jaw
• Lip

Question 16

What do the facial prominences consist of?

Answer 16

Mesenchyme with a covering of ectoderm

Question 17

What will eventually happen to the facial prominences?

Answer 17

They will fuse together to complete the face

Question 18

What results from the failure of fusion of the facial prominences?

Answer 18

Facial clefts and cleft lip

Question 19

What is the first evidence of nose formation?

Answer 19

The apperance of bilateral ectodermal thickenings, the nasal placodes

Question 20

Where do the nasal placodes first appear?

Answer 20

On the venterolateral aspect of the frontonasal prominence

Question 21

What happens to the nasal placodes?

Answer 21

They invaginate to form the nasal pits

Question 22

What is the entrance of each nasal pit?

Answer 22

The nostril

Question 23

What forms around the entrance to each nostril?

Answer 23

A horse-shoe shaped ring

Question 24

What are the ‘arms’ of the horseshoe around the nostril?

Answer 24

The medial and lateral nasal prominences

Question 25

Where do the deepening nasal pits lie?

Answer 25

Dorsal to the stomodaeum

Question 26

What seperates the nasal pits?

Answer 26

A thin sheet of cells, the oronasal membrane

Question 27

What happens to the oronasal membrane?

Answer 27

It disappears, and the oral and nasal cavities become one continuous space

Question 28

In what direction does the maxillary prominence grow?

Answer 28

Medially

Question 29

What happens when the maxillary prominences grow medially?

Answer 29

They push the nasal prominences closer together in the midline

Question 30

What do the maxillary prominences fuse with?

Answer 30

The medial nasal prominences

Question 31

Where do the medial nasal prominences fuse?

Answer 31

In the midlien

Question 32

What does the seperation of the oral and nasal cavity require?

Answer 32

The development of the palate

Question 33

What does the development of the palate involve?

Answer 33

Both the maxillary and medial nasal prominences

Question 34

What happens when the medial nasal prominences fuse in the midline?

Answer 34

It seperates the nostrils from the mouth

Question 35

What does the seperation of the nostrils from the mouth by the fusion of the medial nasal prominences give rise to?

Answer 35

* Philtrum of the upper limb (groove) * Median part of the maxillary bone, with itrs four incisor teeth * Primary palate (or premaxillary portion)

Question 36

What is the primary palate?

Answer 36

A small midline component of the palate

Question 37

What grows from each maxillary prominence?

Answer 37

A palatal shelf

Question 38

In what direction does the palatal shelf grow?

Answer 38

Towards the midline

Question 39

What happens to the palatal shelves?

Answer 39

They fuse with each other, and with the primary palate

Question 40

What creates the secondary palate?

Answer 40

Fusion

Question 41

What does the secondary palate do?

Answer 41

Seperates the nasal cavity from the oral cavity

Question 42

What does the mandible need to grow large enough to do?

Answer 42

Allow the tongue to 'drop' out of the way, allowing the fusion of the palatal shelves

Question 43

How does the nasal septum develop?

Answer 43

As a midline down-growth

Question 44

What ultimately happens to the nasal septum?

Answer 44

It fuses with the palatal shelves

Question 45

What does a cleft palate result from?

Answer 45

Failure of one or both of the palatal shelves to reach the midline and fuse with its counterpart

Question 46

What does a lateral cleft lip result from?

Answer 46

Failure of fusion of the medial nasal prominence and maxillary prominence

Question 47

What is a cleft lip combined with in a cleft palate?

Answer 47

Failure of platal shelves to meet in midline

Question 48

When does the development of the eyes begin?

Answer 48

In the 4th week

Question 49

How does the development of the eyes begin?

Answer 49

With out-pockets of the forebrain

Question 50

What happens to the out-pockets of the forebrain in development of the eyes?

Answer 50

They grow to make contact with the overlying ectoderm,

Question 51

What does the contact between the out-pockets of the brain and the overlying ectoderm cause?

Answer 51

Changes in the ectoderm that form the optic placodes

Question 52

What do the optic placodes become?

Answer 52

The lens of the eyes

Question 53

What happens to the optic/lens placodes do after formation?

Answer 53

Invaginate and pinch off

Question 54

When do eyelids begin to develop?

Answer 54

At the end of the embryonic period (week 8)

Question 55

Describe the developmental programme of the eyelids

Answer 55

They are fused together during the second trimester, and reopen in the third

Question 56

Where are the primordia of the eyes positioned?

Answer 56

On the side of the head

Question 57

What happens to the eyes as the facial prominences grow?

Answer 57

The eyes move to the front of the face

Question 58

What does the external auditory meatus develop from?

Answer 58

The 1st pharyngeal cleft

Question 59

What do the auricles develop from?

Answer 59

Within and 1st and 2nd pharyngeal arch

Question 60

Which auricles develop from the 1st pharyngeal arch?

Answer 60

* Malleus * Incus

Question 61

What develops from the 2nd pharyngeal arch?

Answer 61

Stapes

Question 62

What are the otic placodes made from?

Answer 62

Ectoderm that thickens before sinking

Question 63

What happens when the otic placodes invaginate?

Answer 63

They form the auditory vesicles

Question 64

Where do the external ears intially develop?

Answer 64

In the neck

Question 65

What happens to the ears as the mandible grows?

Answer 65

The ears ascend to the side of the head to lie in line with the eyes

Question 66

What common chromosomal abnormalities have associated external ear abnormalities?

Answer 66

All

Question 67

What does alcohol during pregnany cause?

Answer 67

Classic facial symptoms; * Small eye/nose opening * Thin Philtrum * Under-developed jaw

Question 68

What is the safe level of alcohol consumption during pregnancy?

Answer 68

No known safe level

Question 69

What organs development is known to be sensitive to alcohol?

Answer 69

The brain

Question 70

What is pathology of the brain related to alcohol during pregnancy traced back to?

Answer 70

Migration of neural crest cells