13.0 Development of Orofacial Structures

Question 1

What are the cartilaginous parts of the neurocranium? What are the membranous parts?

Answer 1

Cartilaginous: occipital bone, body of sphenoid bone, ethmoid bone, petrous and mastoid parts of the temporal bone. Membranous: Calvaria (frontal and parietal bones)

Question 2

What are the cartilaginous parts of the viscerocranium? What are the membranous parts?

Answer 2

Cartilaginous: Structures from pharyngeal arches (see image)

Membranous: Maxillary prominence, squamous part of temporal bone, maxilla, zygomatic bone

Question 3

What is the most common form of craniosynostosis?

Answer 3

Scaphocephaly (sagittal suture). Long, narrow, wedge shaped suture.

Question 4

Brachycephaly is a premature closue of what suture?

Answer 4

The entire coronal suture

Question 5

Plagiocephalyis a premature closue of what suture?

Answer 5

One side of the coronal suture

Question 6

Trigonocephalyis a premature closue of what suture?

Answer 6

Frontal (metopic) suture

Question 7

What are the 5 facial primordia? When do they appear?

Answer 7

2 Maxillary prominences

2 Mandibular prominences

1 Frontonasal priminence

They appear around week 4.

Question 8

What are the nasal placodes?

Answer 8

Bilateral oval thickenings of surface ectoderm on the inferolateral portion of the frontonasal priminence. Forms the medial and lateral nasal prominences, which then forms the primordial nares.

Question 9

Describe the development of the auricular primordia.

Answer 9

6 auricular hillcocks form around 1st pharyngeal groove. Development of the mandible pushes ears from neck to side of head at the level of the eyes.

Question 10

What separates the primordial nasal sacs? When does it rupture?

Answer 10

The oronasal membrane. Ruptures in week 6.

Question 11

What forms the primary palate?

Answer 11

Fusion of the two median nasal prominences

Question 12

What forms the secondary plate?

Answer 12

Develops from the lateral palatine processes (palatal shelves)

Question 13

What forms the nasal spetum?

Answer 13

Downward growth of internal parts of merged medial nasal prominences. Fuses with lateral palatine processess.

Question 14

What are some of the risk factos for celft lip and palate?

Answer 14

Genetics: SATB2, TGF-alpha, TGF-beta, IRF6

Environmental: antiepileptic drugs, smoking, binge drinking, folate deficiency, obesity

Question 15

What is choanal atresia?

Answer 15

Bony abnormalities of the pterygoid plates and midfacial growth abnormalities that can cause airway obstruction, noisy breathing, and cyanosis.

Question 16

What forms the oral (anterior 2/3) portion of the tongue?

Answer 16

Median lingual swelling (median tongue bud) and 2 lateral tongue swellings (distal tongue buds)

Question 17

What forms the pharyngeal portion of the tongue?

Answer 17

The copula (from PA 2) and the hypopharyngeal eminence (from PA 1). Hypopharyngeal eminence eventually overgrows copula.

Question 18

What is glossoschissis?

Answer 18

A bifid tongue

Question 19

What is ankyloglossia?

Answer 19

Short lingual frenulum. Can present with problems breast feeding and speaking.

Question 20

What are the dental laminae?

Answer 20

U-shaped bands of oral epithelium that follows the curves of the primitive jaws.

Question 21

What are the 3 main components of a tooth bud?

Answer 21

Enamel organ

Dental papilla

Dental follicle/sac

Question 22

What is the enamel organ made of?

Answer 22

Ectodermal cells from the dental lamina

Question 23

What is the dental papilla?

Answer 23

The internal part of the tooth bud. Eventually makes dentin and pulp.

Question 24

What is the dental follicle/sac?

Answer 24

Mesenchyme surrounding dental papilla and enamel organ. Eventually makes cementum.

Question 25

What occurs during the bell stage of teeth development?

Answer 25

Odontoblasts invade and calcifies predentin to become dentin. Ameloblasts are activated in response to dentin production and produces enamel. Enamel organ becomes bell shaped due to differentiation of enamel.

Question 26

What forms the periodontal ligaments?

Answer 26

Outer cells of the dental sac