Embryology - Development of mouth and face

Question 1

When is the stomadeum present?

Answer 1

Third week:
- SOmites appear and the buccopharyngeal membrane breaks down.

Question 2

When the embryo is 3mm long and in its 4th week what happens?

Answer 2

The frontonasal process and the beginning of mandibular and hyoid arches appear.

Question 3

When do teeth start forming?

Answer 3

Six weeks.

Question 4

How big is the embryo at 6 weeks?

Answer 4

12mm long.

Question 5

When does calcification of the first dentine occur?

Answer 5

In the 5th month, followed closely by enamel.

Question 6

What bounds the stomodeum?

Answer 6

Mandibular arch.

Question 7

What does the mandibular arch produce?

Answer 7

1. Floor of the mouth.
2. Lower jaw.
3. Lower lip.
4. Two maxillary processes.

Question 8

What is the mandibular arch’s cranial boundary?

Answer 8

Forebrain capsule.

Question 9

What does the forebrain capsule develop into?

Answer 9

Frontonasal processes.

Question 10

How is the frontonasal processes identified?

Answer 10

Two nasal pits:
1. Median processes.
2. Two lateral nasal processes.

Question 11

How is the median process characterised?

Answer 11

By a pair of convex globular processes.

Question 12

What happens to the lateral nasal processes?

Answer 12

They unite with the globular processes to encircle the nostril.

Question 13

What does the maxillary and lateral nasal processes encircle?

Answer 13

The eye - they meet together alon the line of nasolacrimal duct.

Question 14

Where on the facade does the maxillary process unite?

Answer 14

In the midline below the nostril. To produce the whole of the upper lip and the maxillae.

Question 15

What does the frontonasal processes produce?

Answer 15

Pre-maxilla - which is covered over by medial extensions of the maxilla in man.

Question 16

How is the upper part of the face formed?

Answer 16

By fusion of the frontonasal and maxillary processes. However, it’s just a mask at first, as the nasal septum and palate have yet to be completed.

Question 17

Where does the developing tongue lay?

Answer 17

Against the floor of the cranium.

Question 18

How does the nasal septum form?

Answer 18

A midline flange grows down from the base of the forebrain capsule (mesenchymal precursor of the skull).

Question 19

What grows from each maxillary process?

Answer 19

Flange - palatial process grows medically across the dorsum of the tongue.

Question 20

What happens when the nasal septum and the two palatal processes meet?

Answer 20

They unite from before backwards, they separate the nasal cavities from each other and also separate the cavities from the mouth.

Question 21

What forms the nasal capsule?

Answer 21

Mesoderm.

Question 22

When does chondrification of the nasal capsule occur?

Answer 22

By the 6th week.

Question 23

What also occurs at the 6th week?

Answer 23

THe nasal walls and hard palate are outlines by a thin layer of hyaline cartilage.

Question 24

When does ossification of the hyaline cartilage in the nasal capsule begin?

Answer 24

After 6 weeks.

Question 25

What happens to the hyaline cartilage in the upper part of the wall of the nose?

Answer 25

The hyaline cartilage is replaced by bone.

Question 26

What happens to the hyaline cartilage in the lower part of the septum and the hard palate?

Answer 26

There is deposition of membrane bone on each surface of the hyaline cartilage.

Question 27

What becomes of the hyaline cartilage after there is deposition of membrane bone on each surface?

Answer 27

It becomes sandwiched between two lawyers of membranous bone and is not absorbed until some time after birth.

Question 28

What innervates all of these structures (inside and outside)?

Answer 28

Fifth cranial nerve - trigeminal nerve.

Question 29

What supplies the frontonasal process and its derivatives?

Answer 29

Ophthalmic division of the trigeminal nerve.

Question 30

What supplies the maxillary process and its derivatives?

Answer 30

Maxillary division.

Question 31

What supplies the lower jaw?

Answer 31

Mandibular division of the trigeminal nerve.

Question 32

What are the most commonest abnormalities in mouth development?

Answer 32

1. Cleft palate.
2. Hare lip

Question 33

What is the occurrence of cleft palate?

Answer 33

1 in 1000.

Question 34

What is the occurrence of Harelip?

Answer 34

1 in 2500.

Question 35

What is harelip?

Answer 35

Where the defect runs almost always lateral. The cleft runs down from the nostril.

Question 36

How does harelip occur?

Answer 36

The median part of the lip is derived from the opposite maxillary process or from the frontonasal process.

Question 37

How does cleft palate form?

Answer 37

The two palatal processes unite with each other (and with the nasal septum) from before backwards. There is arrest of this union.

Question 38

What happens in severe cleft palate?

Answer 38

There is no union from the uvula to the gum margin. It always runs between premaxilla nd maxilla nad involves the jaw between the lateral incisor and canine teeth.

Question 38

What happens in severe cleft palate?

Answer 38

There is no union from the uvula to the gum margin. It always runs between premaxilla nd maxilla nad involves the jaw between the lateral incisor and canine teeth.

Question 39

What happens in severe cleft palate?

Answer 39

There is no union from the uvula to the gum margin. It always runs between premaxilla nd maxilla nad involves the jaw between the lateral incisor and canine teeth.

Question 39

What happens in severe cleft palate?

Answer 39

There is no union from the uvula to the gum margin. It always runs between premaxilla nd maxilla nad involves the jaw between the lateral incisor and canine teeth.

Question 40

What is a less common facial defect?

Answer 40

Facial cleft forms along the line of nasolacrimal duct, when there is failur of fusion of the lateral nasal process with the maxillary process.