"Gross Anatomy Development of the Face and Palate Jeffrey Amack" MARY

Question 1

Pharyngeal arches are prominent features of the developing head and neck. They are also called branchial arches because they resemble the gills of a fish. When do these arches develop?

Answer 1

Arches form in a rostral to caudal sequence: Arch 1 to 6 from week 4 onwards, Arch 1 and 2 appear at the time of closure of the cranial neuropore (Day 25).

Question 2

The pharyngeal arches have grooves called:

Answer 2

Pharyngeal clefts on the exterior, and pharyngeal pouches on the interior.

Question 3

The musculature of the face and neck derives from:

Answer 3

mesoderm

Question 4

What developmental tissues are the progenitors of the pharyngeal arches?

Answer 4

Mesenchymal core - ectoderm on outside, endoderm on inside, mesoderm in the middle, plus neural crest cells that migrate into the arches

Question 5

Each pharyngeal arch has certain elements associated with it:

Answer 5

A specific cranial nerve
An aortic arch artery
A cartilagenous rod derived from neural crest cells or lateral plate mesoderm (to form muscle)

Question 6

What do neural crest cells give rise to?

Answer 6

Neural, skin, teeth, head, face, heart, endocrine, gastrointestinal tract

Question 7

T/F: Neural crest cells do not follow distinct migration patterns. They travel indiscriminately as the embryo develops.

Answer 7

False. Neural crest cells migrate in three streams to the pharyngeal arches. Rhombomeres are patterned by a Hox code—NCCs take Hox expression with them. Differential hox expression allows NCCs to respond differently to signals from pouch endoderm.

Question 8

The face is primarily derived from what pharyngeal arches?

Answer 8

1 and 2

Question 9

Pharyngeal arches 3 and 4 contribute to form the:

Answer 9

neck (and 6)

Question 10

Name the notable structures formed by pharyngeal arch #1.

Answer 10

Meckel's cartilage
Malleus
Incus
Ligaments
Mandible

Question 11

Reichert’s cartilage, stapes, temporal bone styloid process and hyoid bone form from:

Answer 11

pharyngeal arch #2

Note that hyoid is also formed from arch #3.

Question 12

Which pharyngeal arches primarily contribute to muscles that make up the face?

Answer 12

Mostly arches 1 and 2: 1 for muscles of mastication, 2 for muscles of facial expression.
Arches 3 and 4 contribute small muscles in the area of the larynx and pharynx.

Question 13

T/F: Distinct cranial nerves innervate pharyngeal pouches.

Answer 13

True. 
Arch 1 - CN V and some other stuff
Arch 2 - CN VII
Arch 3 - CN IX
Arch 4 - CN X and some other stuff

Question 14

What are the characteristics of Pierre Robins Syndrome (Pierre Robins sequence)?

Answer 14

1. malformation of first arch structures
2. triad of micrognathia, cleft palate and glossoptosis (posteriorly placed tongue)
3. difficulties breathing and feeding

Question 15

Treacher Collins syndrome results from defects in what?

Answer 15

Pharyngeal arches 1 and 2 - leads to several craniofacial features ie downward slating eyes (hunchback of notre dame look)

Question 16

What is the genetic defect in Treacher Collins syndrome?

Answer 16

TCOF1 gene, which leads to overactive p53 in the face during development ie. apoptosis of neural crest cells

Question 17

T/F: Reducing p53 expression in mice can ameliorate the effects of a defective TCOF1 gene, as seen in Treacher Collins syndrome.

Answer 17

True

Question 18

Pharyngeal cleft # ___ gives rise to the external auditory meatus.

Answer 18

1

Question 19

How might a branchial fistula arise?

Answer 19

If the second pharyngeal arch fails to cover the 3rd and 4th

Question 20

The first pharyngeal pouch forms:

Answer 20

Tympanic cavity and auditory (Eustachian) tube

Question 21

What pharyngeal pouch forms the palatine tonsil?

Answer 21

Second

Question 22

The third pharyngeal pouch becomes the:

Answer 22

inferior parathyroid gland
thymus
Remember this “T” for third, paraThyroid, thymus

Question 23

What pharyngeal pouch forms the superior PTH gland and ultimobranchial body?

Answer 23

Fourth

Question 24

On what side of the pharynx does the thyroid form?

Answer 24

Ventral

Question 25

The foramen cecum becomes part of what muscle?

Answer 25

Tongue. Interestingly, all four pharyngeal pouches contribute to the formation of the tongue

Question 26

How does ankylglossia occur? This might be a question, considering Amack has a personal connection to it.

Answer 26

Tongue tie, abnormal lingual frenulum

Question 27

T/F: The thyroid gland is a pharyngeal pouch derivative.

Answer 27

False: The thyroid, which is not a pharyngeal pouch derivative, migrates along the thyroglossal duct.

Question 28

Expansion of the facial prominences form the face at about what week gestation?

Answer 28

Week 6 to 7

Facial processes that emerge in the fourth week are the maxillary, mandibular and frontonasal prominences.

Question 29

How does cleft lip develop?

Answer 29

Cleft lip results from failed fusion of the maxillary and

medial nasal prominences.

Question 30

What is palatogenesis?

Answer 30

Fusion of primary and secondary plates

Question 31

What interactions initiate tooth development?

Answer 31

Oral epithelium and neural crest-derived mesenchyme

Question 32

Odontoblasts differentiate from the:

Answer 32

Dental papilla (to produce dentin)

Question 33

How does enamel form?

Answer 33

Ameloblasts differentiate from the inner dental epithelium to produce enamel

Question 34

Defective enamel formation is characteristic of what tooth formation defect?

Answer 34

Amelogenesis imperfecta