Embryology of the face and oral cavity Flashcards
During the 3rd embryonic week, the crown-rump measurement is ___mm.
3
What week starts the fetal stage? What is the crown-rump measurement during this stage?
8th week
30mm or 3cm
The ___ appears in the ___ embryonic week and becomes the nasal and oral cavities between the ___ and ___ embryonic weeks.
stomodeum; 3rd; 6th; 8th
What is the superior, inferior and posterior boundaries of the stomodeum during the 3rd embryonic week?
Superior - frontal prominence
Inferior - cardiac plate
Posterior - buccopharyngeal membrane
The buccopharyngeal membrane separates the stomodeum from the ___.
foregut (future oral pharynx)
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).
buccopharyngeal; ectoderm; endoderm; foregut
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.
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.
The branchial arches are separated externally by small clefts called branchial ___ and internally the corresponding small depressions are called pharyngeal ___.
grooves; pouches
What appears during the 4th embryonic week?
4 paired branchial arches and branchial clefts/grooves
In the 4th week, the arch I becomes the right and left ___ and ___ facial processes.
maxillary; mandibular
The place where the upper maxillary and lower mandibular processes meet at either side of the stomodeum becomes the ___ ___ ___.
commissura labiorum oris
What replaces the cardiac plate as the lower boundary of the stomodeum?
2 mandibular facial processes
The 2 ___ facial processes become the posteriorlateral boundaries of the stomodeum.
maxillary
Where do the nasal pits appear?
within the frontal prominences
After appearance of of nasal pits, what three processes does the frontal prominence become?
median nasal facial process
right and left lateral nasal processes
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.
pits; ducts; nostrils; nasal
The frontal prominence becomes ___ of seven facial processes and the branchial arch I becomes ___ of seven.
3; 4
What are the 3 frontal prominence that become the facial processes?
median nasal process
right lateral nasal process
left lateral nasal process
What are the 4 branchial arch I that become the facial processes?
right maxillary process
left maxillary process
right mandibular process
left mandibular process
What is the fate of the OUTER surface of the median nasal process?
midline of nose
philtrum of upper lip
What is the fate of the OUTER surface of the lateral nasal process?
lateral sides and ala of nose
infraorbital part of face
What is the fate of the OUTER surface of the maxillary process?
upper part of cheeks
lateral parts of upper lip
What is the fate of the OUTER surface of the mandibular process?
lower part of cheeks
lower lip
chin
What does each cleft I become?
the external auditory meatus
Each arch II becomes an embryonic fold of tissue called the ___.
operculum
What arches and clefts does the operculum cover?
arches III and IV
clefts II, III, IV
The operculum becomes the sides of ___ below the ___ ___ ___.
neck; external auditory meatus
What can occur if the operculum epithelium does not fuse with the branchial arch epithelium?
a sinus is created that can lead to a cyst on the side of the neck
The groove between the maxillary and median nasal processes extend into what structure?
stomodeum
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.
maxillary; median; 5; lip
If the ___ processes do not merge with each other by the 5th embryonic week, clefting of the lower jaw occurs.
mandibular
What is the stomodeum side of the median nasal process?
primary palate
When does the fetal period start?
week 8, the mandible appears retrognathic to other structures
The ___ membrane ruptures allowing opening to the foregut that becomes the nasal and oral pharynx.
buccopharyngeal
What is the site of the anterior pillar or fauces?
the buccophayngeal membrane
___ lingual swellings appear during the ___th embryonic week and merge to become the tongue.
Four; 4th
What are the 4 lingual swellings?
right lateral lingual swelling
left lateral lingual swelling
tuberculum impar
copula
What lingual swellings become the anterior two-thirds of the tongue?
tuberculum impar and 2 lateral lingual swellings
What structure becomes the posterior third or root of the tongue?
copula
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.
True.
T/F. By week 5 the tongue is under-developed and the stomodeum begins to partition into oral and nasal cavities.
False, the tongue is well developed and the stomodeum partitions into oral and nasal cavities during week 6.
What three structures appear in the stomodeum during the 5th embryonic week?
primary palate
nasal septum
palatine folds
Where does the primary palate arise from? nasal septum? palatine folds?
primary palate - median nasal facial process
nasal septum - primary palate
palatine folds - inner surface of maxillary facial process
During the fifth embryonic week, what position are the palatine folds in?
vertical
The palatine folds have lining epithelium that is connected to an underlying mesenchymal tissue also called ___.
ectomesenchyme
Tissue from the neck up is ectomesenchyme
Tissue from the neck down is mesoderm
What epithelial structures fuse during the 6th embryonic week to form the palate?
primary palate
nasal septum
palatine folds
T/F. Epithelial fusion progresses posteriorly where the epithelium of palatine folds fuse with each other and with epithelium of nasal septum.
True.
T/F. The fused epithelium breaks-up and there is intermingling of mesenchymal cells.
True.
When the epithelium is gone and the mesenchyme union is completed, the ___ palate is formed along with the ___ and ___ cavities.
secondary; oral; nasal
What weeks do epithelial fusion and mesenchymal union occur?
between 6 and 8 weeks IU+
