EMBRYOLOGY OF HEAD, FACE AND ORAL CAVITY

Question 1

What are branchial (pharyngeal) arches and when do they form

Answer 1

they are bilateral small swellings or bumps on either side of embryo inferior to the stomodeum and they form during the 4th week of embryonic development

Question 2

which branchial arch is the most prominent in humans

Answer 2

4th branchial arch

Question 3

which branchial arches will fuse with 4th

Answer 3

5th and 6th branchial arches

Question 4

define stomodeum

Answer 4

primitive mouth or oral cavity in embryo

Question 5

branchial arches are separated by

Answer 5

-branchial grooves externally
-pharyngeal pouches internally

Question 6

branchial arches are covered by

Answer 6

-externally by ectoderm
-internally endoderm

Question 7

branchial arches support which lateral wall

Answer 7

they support lateral walls of primitive pharynx by forming structures on sides of developing throat

Question 8

list down the anatomy of branchial arch

Answer 8

• cartilage rod “derived from ectoderm”
  -vascular component” derived from mesoderm”
  -muscular component” derived from mesoderm”
  -neural component” derived from neural crest cells “type of ectomesoderm”

Question 9

1st branchial arch is called

Answer 9

Mandibular arch

Question 10

1st arch gives rise to

Answer 10

maxilla, mandible , lower face and mandibular teeth

Question 11

1st arch cartilage is

Answer 11

meckel cartilage forms early in development within 1st branchial arch it serves as template for development of LOWER MANDIBLE

Question 12

1st arch give rise to muscles responsible for chewing list them

Answer 12

masseter
temporalis
lateral pterygoid
medial pterygoid

Question 13

1st arch is innervated by

Answer 13

-trigeminal nerve( V cranial nerve) which give us sensory and motor function

Question 14

the 1st arch contribute to form 2 arteries list them

Answer 14

maxillary artery
external carotid artery

Question 15

what is the 2nd branchial arch called

Answer 15

hyoid arch

Question 16

2nd arch gives rise to

Answer 16

muscles of facial expression

Question 17

what is the name of the cartilage in 2nd arch

Answer 17

Reichert cartilage which form a key component in 2nd branchial arch and contributes to development of structures
-stapes
-styloid process of temporal
-superior hyoid bone

Question 18

2nd arch is innervated by

Answer 18

facial nerve (VII cranial nerve)

Question 19

in the 3rd branchial arch what do we have

Answer 19

cartilage is derived from the 3rd arch and contributes to formation of lower aspect of hyoid bone

Question 20

3rd branchial arch is innervated by

Answer 20

glossopharyngeal nerve ( cranial nerve IX)

Question 21

what do the 4th and 5th branchial arches form

Answer 21

Thyroid and other laryngeal cartilages

Question 22

which are arches arches involved in the tongue formation

Answer 22

1st , 3rd, and 4th

Question 23

4th branchial arch is innervated by

Answer 23

vagus nerve

Question 24

meckel cartilage gives us in the future

Answer 24

Incus
Malleus

Question 25

list the events that occur during WEEK 4

Answer 25

face begins to take shape with frontal process as its main structure and maxillary process on either side and under it we have the mandible which is divided into two

Question 26

between week 4-7

Answer 26

max and mand processes from 1st arch begin to move towards other and fuse

Question 27

in week 4 what will the maxillary process give us

Answer 27

• maxilla
• zygomatic bone
• squamous part of temporal bone

Question 28

between maxilla and mandible we have what and its separated by what in week 4

Answer 28

stomodeum and separated from developing gut by buccopharyngeal membrane comes from ectoderm and endoderm

Question 29

when will buccopharyngeal membrane rupture

Answer 29

week 5 allowing stomodeum to connect with digestive tract

Question 30

list what happened in week 5

Answer 30

-The frontonasal process will diminish causing face to become wider
- eye become clearly visible on sides
- nasal placodes will develop they are 2 oval thickening epithelium on either side of frontonasal
- nasal cavity opens into oral pit by the 2 nasal openings that were formed by growth of the nasal placodes known as nostrils

Question 31

list what happens in week 6

Answer 31

-face broadens causing eye to move more central

-stomodeum widens and attaches laterally to each of mand and max arches

-maxilla and lateral nasal processes fuse and at this point of fusion they form nasolacrimal groove and the groove will become nasolacrimal duct

• the lateral nose process forms the alae of nose
• mandibular fuse to form lower jaw

-odontogenic epithelium appears around 38 days

Question 32

in week 6 the two medial nasal processes will fuse to form and give us

Answer 32

form intermaxillary segment and give us

-anterior part of maxilla
-philtrum
-primary palate
-lower part of nose

Question 33

what happens to the 1st branchial groove in week 6

Answer 33

become external auditory canal (external acoustic meatus)

Question 34

external ear is formed by the fusion of how many hillocks

Answer 34

6 hillocks:
3 from mandibular arch
3 from hyoid arch

Question 35

in week 7

Answer 35

face takes more human appearance
eyes are in middle
upper lip has fused
external ear developed