Embryology of the face and oral cavity

Question 1

During the 3rd embryonic week, the crown-rump measurement is ___mm.

Answer 1

3

Question 2

What week starts the fetal stage? What is the crown-rump measurement during this stage?

Answer 2

8th week

30mm or 3cm

Question 3

The ___ appears in the ___ embryonic week and becomes the nasal and oral cavities between the ___ and ___ embryonic weeks.

Answer 3

stomodeum; 3rd; 6th; 8th

Question 4

What is the superior, inferior and posterior boundaries of the stomodeum during the 3rd embryonic week?

Answer 4

Superior - frontal prominence
Inferior - cardiac plate
Posterior - buccopharyngeal membrane

Question 5

The buccopharyngeal membrane separates the stomodeum from the ___.

Answer 5

foregut (future oral pharynx)

Question 6

The ___ membrane is a bilaminar structure consisting of apposed ___ and ___ that separates the stomodeum from the ___ (but this soon breaks down so that the stomodeum communicates directly with the foregut).

Answer 6

buccopharyngeal; ectoderm; endoderm; foregut

Question 7

T/F. The branchial arches form in the pharyngeal wall, which first consist of a sheet of lateral plate mesoderm sandwiched between endoderm externally and ectoderm internally.

Answer 7

False, The branchial arches form in the pharyngeal wall, which first consist of a sheet of lateral plate mesoderm sandwiched between ECTODERM externally and ENDODERM internally.

Question 8

The branchial arches are separated externally by small clefts called branchial ___ and internally the corresponding small depressions are called pharyngeal ___.

Answer 8

grooves; pouches

Question 9

What appears during the 4th embryonic week?

Answer 9

4 paired branchial arches and branchial clefts/grooves

Question 10

In the 4th week, the arch I becomes the right and left ___ and ___ facial processes.

Answer 10

maxillary; mandibular

Question 11

The place where the upper maxillary and lower mandibular processes meet at either side of the stomodeum becomes the ___ ___ ___.

Answer 11

commissura labiorum oris

Question 12

What replaces the cardiac plate as the lower boundary of the stomodeum?

Answer 12

2 mandibular facial processes

Question 13

The 2 ___ facial processes become the posteriorlateral boundaries of the stomodeum.

Answer 13

maxillary

Question 14

Where do the nasal pits appear?

Answer 14

within the frontal prominences

Question 15

After appearance of of nasal pits, what three processes does the frontal prominence become?

Answer 15

median nasal facial process

right and left lateral nasal processes

Question 16

Nasal ___ deepen and become nasal ___ that open into the stomodeum. The ducts become ___ that open into ___ cavities during the formation of nasal and oral cavities.

Answer 16

pits; ducts; nostrils; nasal

Question 17

The frontal prominence becomes ___ of seven facial processes and the branchial arch I becomes ___ of seven.

Answer 17

3; 4

Question 18

What are the 3 frontal prominence that become the facial processes?

Answer 18

median nasal process
right lateral nasal process
left lateral nasal process

Question 19

What are the 4 branchial arch I that become the facial processes?

Answer 19

right maxillary process
left maxillary process
right mandibular process
left mandibular process

Question 20

What is the fate of the OUTER surface of the median nasal process?

Answer 20

midline of nose

philtrum of upper lip

Question 21

What is the fate of the OUTER surface of the lateral nasal process?

Answer 21

lateral sides and ala of nose

infraorbital part of face

Question 22

What is the fate of the OUTER surface of the maxillary process?

Answer 22

upper part of cheeks

lateral parts of upper lip

Question 23

What is the fate of the OUTER surface of the mandibular process?

Answer 23

lower part of cheeks
lower lip
chin

Question 24

What does each cleft I become?

Answer 24

the external auditory meatus

Question 25

Each arch II becomes an embryonic fold of tissue called the ___.

Answer 25

operculum

Question 26

What arches and clefts does the operculum cover?

Answer 26

arches III and IV

clefts II, III, IV

Question 27

The operculum becomes the sides of ___ below the ___ ___ ___.

Answer 27

neck; external auditory meatus

Question 28

What can occur if the operculum epithelium does not fuse with the branchial arch epithelium?

Answer 28

a sinus is created that can lead to a cyst on the side of the neck

Question 29

The groove between the maxillary and median nasal processes extend into what structure?

Answer 29

stomodeum

Question 30

If the ___ facial process or processes do not merge with the ___ nasal facial process by the ___th embryonic week, unilateral or bilateral clefting of the upper ___ occurs.

Answer 30

maxillary; median; 5; lip

Question 31

If the ___ processes do not merge with each other by the 5th embryonic week, clefting of the lower jaw occurs.

Answer 31

mandibular

Question 32

What is the stomodeum side of the median nasal process?

Answer 32

primary palate

Question 33

When does the fetal period start?

Answer 33

week 8, the mandible appears retrognathic to other structures

Question 34

The ___ membrane ruptures allowing opening to the foregut that becomes the nasal and oral pharynx.

Answer 34

buccopharyngeal

Question 35

What is the site of the anterior pillar or fauces?

Answer 35

the buccophayngeal membrane

Question 36

___ lingual swellings appear during the ___th embryonic week and merge to become the tongue.

Answer 36

Four; 4th

Question 37

What are the 4 lingual swellings?

Answer 37

right lateral lingual swelling
left lateral lingual swelling
tuberculum impar
copula

Question 38

What lingual swellings become the anterior two-thirds of the tongue?

Answer 38

tuberculum impar and 2 lateral lingual swellings

Question 39

What structure becomes the posterior third or root of the tongue?

Answer 39

copula

Question 40

T/F The 4 lingual swellings span along the ventral, inside surface of the mandibular process of branchial arch I, and between II and III.

Answer 40

True.

Question 41

T/F. By week 5 the tongue is under-developed and the stomodeum begins to partition into oral and nasal cavities.

Answer 41

False, the tongue is well developed and the stomodeum partitions into oral and nasal cavities during week 6.

Question 42

What three structures appear in the stomodeum during the 5th embryonic week?

Answer 42

primary palate
nasal septum
palatine folds

Question 43

Where does the primary palate arise from? nasal septum? palatine folds?

Answer 43

primary palate - median nasal facial process
nasal septum - primary palate
palatine folds - inner surface of maxillary facial process

Question 44

During the fifth embryonic week, what position are the palatine folds in?

Answer 44

vertical

Question 45

The palatine folds have lining epithelium that is connected to an underlying mesenchymal tissue also called ___.

Answer 45

ectomesenchyme
Tissue from the neck up is ectomesenchyme
Tissue from the neck down is mesoderm

Question 46

What epithelial structures fuse during the 6th embryonic week to form the palate?

Answer 46

primary palate
nasal septum
palatine folds

Question 47

T/F. Epithelial fusion progresses posteriorly where the epithelium of palatine folds fuse with each other and with epithelium of nasal septum.

Answer 47

True.

Question 48

T/F. The fused epithelium breaks-up and there is intermingling of mesenchymal cells.

Answer 48

True.

Question 49

When the epithelium is gone and the mesenchyme union is completed, the ___ palate is formed along with the ___ and ___ cavities.

Answer 49

secondary; oral; nasal

Question 50

What weeks do epithelial fusion and mesenchymal union occur?

Answer 50

between 6 and 8 weeks IU+