Head and Neck development

Question 1

Which aortic arch is vestigual?

Answer 1

The fifth aortic arch

Question 2

What do the pharyngeal arches develop into?

Answer 2

Cartilage

Question 3

What embryonic germ layer is the visceralcranial and neurocranial regions derived from?

Answer 3

Visceralcranial - neural crest cells

Neurocranial - paraxial mesoderm (somitomeres)

The laryngeals - lateral plate mesoderm

Question 4

What does the first pharyngeal arch develop into?

Answer 4

Meckel’s cartilage
Malleus
Incus

Question 5

What does the second pharyngeal arch develop into?

Answer 5

Question 6

What does the third pharyngeal arch develop into?

Answer 6

Question 7

What does the fourth pharyngeal and sixth arches develop into?

Answer 7

The laryngeal cartilages

Question 8

What does the fifth pharyngeal arch develop into?

Answer 8

Question 9

What cells migrate into the arches to provide musculature for the craniofacial region?

Answer 9

Paraxial mesoderm

Question 10

What are the homeobox gene involved in craniofacial development?

Answer 10

Neural crest cells bring their genetic codes to help pattern head and neck

Question 11

What patterns the pharyngeal arches and induces differentiation?

Answer 11

The pharyngeal pouches

BMP7, FGF8, and SHH interact with homeobox genes to pattern this tissue

Question 12

Why do cervical sinuses develop?

Answer 12

The failure of the second arch tissue to completely occlude the other clefts

Question 13

What does the endoderm of the first pharyngeal pouch form?

Answer 13

The auditory tube

Question 14

What does the endoderm of the second pharyngeal pouch form?

Answer 14

The pallentine tonsils

Question 15

What does the endoderm of the third pharyngeal pouch form?

Answer 15

Inferior parathyroid and the thymus

Question 16

What does the endoderm of the fourth pharyngeal pouch form?

Answer 16

The superior parathyroid

Question 17

Where is the thyroid derived?

Answer 17

Endoderm from pharynx (foramen cecum)

Tongue develops here as well

First arch forms the body of the tongue - innervated by the trigeminal nerve

The second and third arches form tissue that fuses to form first 1/3 of the tongue (including the root) - innervated by the glossopharyngeal nerve

The epiglottis and very posterior tongue is derived from the fourth pharyngeal arch

Question 18

When does facial development begin?

Answer 18

The fourth week

Question 19

What is a placode?

Answer 19

A sensory organ that forms when the ectoderm thickens (gets taller)

Question 20

Answer 20

Secondary palate formation ( begins at 6.5 weeks)

Palatal shells completely fuse by 10 weeks

Secondary palate is derived from the first pharyngeal arch

Question 21

Defects in the primary palate:

Answer 21

Cleft lip/palate

Frequency: 1 in 700 births
Boys cleft lip w/wo cleft palate = 2x girls
Girls cleft palate = 2x boys

Question 22

What establishes the midline?

Answer 22

Notocord and prechordal plate - SHH

SHH must be bound to cholesterol to distribute properly

Question 23

Answer 23

Mandible

Question 25

Answer 25

Arch endoderm ## Footnote The cells of the pouch endoderm communicate with the paraxial mesoderm (somites and somitomeres)

Question 26

Answer 26

aortic arch, cranial nerve, and cartilage

Question 27

Answer 27

Failure of the mandible to grow

Question 28

Id the major embryonic prominences of the face?

Answer 28