Development of the face

Question 1

What are neural crest cells populations of

Answer 1

Transient populations of ectodermal cells

Question 2

Where do neural crest cells develop

Answer 2

Within the crest if the neural folds in the cranio- caudal axis of the embryo

Question 3

Where do neural crest cells migrate

Answer 3

Many parts of the body where they behave like stem cells

Question 4

What week do the branchial arch appear

Answer 4

3rd week

Question 5

Where do the branchial arch develop

Answer 5

Either side of the developing foregut

Question 6

How many pairs of branchial arches are there

Answer 6

5 (1 to 6)

Question 7

What develops from approx week 4

Answer 7

Small bulges called rhombomeres develop laterally from the developing hindbrain
They migrate forward from the back of the head to where the face and front of neck would be to provide the majority of ectomesenchyme to the development of the pharyngeal structures

Question 8

What separates the head from the cardiac bulge

Answer 8

Pharyngeal arches (they proliferate and migrate forward until they meet their counterpart)

Question 9

What is each arch associated with

Answer 9

• Mesenchyme/ ectomesenchyme
• Specific artery
• Arch associated cranial nerve
• A covering of ectoderm
• A lining of endoderm cartilage

Question 10

Where are the pharyngeal grooves (clefts) located

Answer 10

Between each of the pharyngeal arches

Question 11

What happens to the pharyngeal grooves

Answer 11

Some will develop into pharyngeal pouches. Each branchial arch will grow downwards and forwards

Question 12

How do components of the 3rd and 4th arch grow

Answer 12

Components overgrow the second arch and lie adjacent to the first

Question 13

Name of each of the arches

Answer 13

1st - Mandibular 
2nd - Hyoid 
3rd- third
4th- fourth
6th- sixth

Question 14

What cartilage is associated with the first arch

Answer 14

Meckel’s cartilage

Question 15

What is the importance of Meckel’s cartilage

Answer 15

Posteriorly, each Meckel’s cartilage terminates in an enlargement called the malleus

The malleus lies adjacent to a small cartilage, the incus

Further posteriorly is a third body of cartilage, the stapes

The malleus, incus, and stapes later transform into the hearing bones of the middle ear

, for the first 20 weeks of prenatal life

The contact point between the malleus and incus is the articulation of the lower jaw

The second temporomandibular joint between the condyle and temporal fossa becomes functional later

Early mandible of fetus

Question 16

What is the cartilage derivative of the arches

Answer 16

1st - Malleus, incus, sphenomandibular ligament
2nd- Stapes, stylohyoid ligament, lesser horn and upper part of body of hyoid bone
3rd - Greater horn and lower part of body of hyoid
4th - Thyroid cartilage
6th - Arytenoid cartilage

Question 17

What muscles are associated with each arch

Answer 17

1st - Muscles of mastication, ant belly of digastric, mylohyoid
2nd - Stapedius, stylohyoid, facial muscles, buccinator
3rd - Stylopharnygeus
4th- Pharyngeal and extrinsic laryngeal muscles
6th - Intrinsic laryngeal muscles

Question 18

What nerves are associated with each arch

Answer 18

1st - Mandibular
2nd- Facial 
3rd - Glossopharyngeal
4th - Vagus - superior laryngeal
6th - Vagus - recurrent laryngeal

Question 19

What are the 5 processes that the face develops from

Answer 19

Frontonasal, 2 x mandibular, 2 x maxillary

Question 20

What stops the 2 maxillary processes from meeting

Answer 20

Frontonasal structure

Question 21

Explain the development of the nasal cavity

Answer 21

• The ectoderm of the frontal prominence thickens, forming the nasal placodes
• Then mesoderm underneath the placodes proliferates and forms the nasal pits
• Then there is extension backwards which forms the nasal cavity

Question 22

What are the structures that the anterior 2/3 of the tongue develop from

Answer 22

The structures develop within the primitive stomatodeum. The tuberculum impar (single) and lateral lingual swellings (paired)

Question 23

Where does the thyroid tissue start to develop

Answer 23

Foramen Caecum

Question 24

What branch does the anterior 2/3 of the tongue originate from

Answer 24

First arch

Question 25

What branch does the posterior 1/3 of the tongue originate from

Answer 25

Third and fourth arch

Question 26

What is the anatomical landmark called when the anterior 2/3 and posterior 1/3 meet

Answer 26

Sulcus Terminalis

Question 27

What is Di George syndrome

Answer 27

Deletion of chromosome 22