head and neck embryology

Question 1

What is the phase called when the single layered blastula becomes trilaminar gastrula

Answer 1

gastrulation

Question 2

invaginating epiblast cells have 2 fates:

Answer 2

# 1. fill in between epiblast and hypoblast -\> mesoderm
2. replace hypoblast -\> endoderm

* remaining epiblast cells become ectoderm

Question 3

growth of WHAT causes lateral folding of the trilaminar disc?

Answer 3

somites

Question 4

longitudinal growth of the cranial and caudal ends of the neural plate and tube causes the trilaminar disc to what?

Answer 4

undergo craniocaudal folding

Question 5

The oropharyngeal membrane, which is initially cranial to developing neural tube, is folded inside developing head which seperates what?

Answer 5

pharynx from oral cavity

Question 6

What are pharyngeal arches? Name them

Answer 6

paired bulges along the wall of the developing pharynx

• 5 arches: 1, 2, 3, 4, and 6

Question 7

mesoderm of the pharyngeal arches becomes what?

Answer 7

muscles of the head

Question 8

neural crest cells in the pharyngeal arches contribute to form what?

Answer 8

skeleton of head and neck

Question 9

Name the cranial nerve associated with each of the arches

Answer 9

• arch 1: Trigeminal
• arch 2: Facial
• arch 3: Glossopharyngeal
• arch 4 and 6: Vagus

Question 10

1st pharyngeal arch has 2 processes and 1 cartilage associated with it. Name them

Answer 10

• maxillary process
• mandibular process

*nerve associated CN V*

• Cartilage: Meckel’s cartilage

Question 11

meckel’s cartilage disappears except for 2 small pieces which ossify to form what?

Answer 11

malleus and incus of middle ear

Question 12

Mesenchyme of 1 pharyngeal arch derived from neural crest cells form the bones of

Answer 12

mandible and lower face

Question 13

Mesoderm derived mesenchyme of the 1 pharyngeal arch produces what

Answer 13

dermis of the face and muscles associated with mandible and ear

• CN V innervates all first derived structures: muscles of mastication; tensor tympani and Tensor veli palatini; skin of face

Question 14

nerve of 2nd pharyngeal arch

Answer 14

facial n

Question 15

cartilage of the 2nd pharyngeal arch becomes

Answer 15

• part of body and lesser horn of hyoid
• styloid process
• stylohyoid ligament
• stapes

Question 16

Muscles of the 2nd pharyngeal arch become?

Answer 16

• stylohyoid and posterior digastric
• stapedius
• muscles of facial expression

Question 17

3rd pharyngeal arch becomes what

Answer 17

• greater horn and inferior portion of the body of the hyoid bone
• stylopharyngeus

Question 18

4th pharyngeal arch becomes what

Answer 18

• cartilages of larynx
• cricothyroid, pharyngeal muscles
• superior laryngeal nerve

Question 19

6th pharyngeal arch becomes what

Answer 19

• intrinsic muscles of larynx (except cricothyroid
• recurrent/inferior laryngeal nerve

Question 20

Between the pharyngeal arch swellings, how many external clefts and how many internal pouches develop

Answer 20

• 1 external pharyngeal cleft
• 4 internal pharyngal pouches

Question 21

first pharyngeal pouch and cleft form between first and second arch. What does the cleft become? What does the pouch become?

Answer 21

• cleft -> external auditory canal
• pouch -> tympanic cavity and pharyngotympanic tube

Question 22

what does 2nd pharyngeal pouch become

Answer 22

tonsils

Question 23

What does 3rd pharyngeal pouch become

Answer 23

glands

Question 24

What does 4th pharyngeal pouch become

Answer 24

contributes to C cells of thyroid gland

Question 25

Bones of the face, mandible, and hyoid have what origin

Answer 25

neural crest cells

Question 26

bones of the braincase have what origin

Answer 26

paraxial mesoderm

Question 27

Nasal placodes consist of what 3 parts

Answer 27

* nasal pits * medial nasal prominence * lateral nasal prominence

Question 28

nasal prominences fuse to form what

Answer 28

philtrum: intermaxillary segment

Question 29

maxillary prominences form secondary plate and creates what

Answer 29

palatine shelves

Question 30

fusion of palatine shelves and what completes the formation of the secondary palate

Answer 30

nasal septum

Question 31

Several swellings from the floor of the developing pharynx contribute to the development of what?

Answer 31

tongue

Question 32

Tissues of Tongue have innervation from which arches

Answer 32

1-4

Question 33

innervation of tongue muscles come from what

Answer 33

occipital somites: some mesoderm migrates in to the tongue to produce the muscles and the somite innervation is preserved