L1 Flashcards
During fourth embryonic week
Merging, not
Note: merging, not fusing, takes place between facial processes.
4th embryonic week: The groove seen in the image between maxillary and median nasal processes is gradually
eliminated
If the maxillary process or processes do not merge with the median nasal process by the 5th embryonic week,
unilateral or bilateral clefting of the upper lip occurs
Although rare, if the mandibular processes do not merge with each other by the 5th embryonic week,
clefting of the lower jaw occurs
End of week 4: Groove between
median and maxillary processes is still evident:
its length is lessened and median process is narrower
Merging of facial processes complete by
y 5th embryonic week. If merger is not completed by this week, facial clefts occur
Review of the fate of the 3 boundaries of the stomodeum:
Frontal prominence:
after the appearance of nasal pits becomes:
* right and left lateral nasal facial processes * median nasal facial process
Review of the fate of the 3 boundaries of the stomodeum:
Cardiac plate:
*replaced by the mandibular facial processes during 4th week IU
Review of the fate of the 3 boundaries of the stomodeum:
Buccopharyngeal membrane
*ruptures in 4th week allowing opening to the foregut that becomes the nasal and oral pharynx
Note: the buccopharyngeal membrane is the site of the pillar of fauces
Boundaries of Stomodeum (S):
3rd embryonic week
Superior: 1 = Frontal prominence
Inferior: 2 = Cardiac plate
Posterior 3 = Buccopharyngeal membrane
Tongue : Appearance and Formation during
fourth embryonic week.
Four lingual swellings appear during the 4th embryonic week along the ventral, inside surface
of mandibular process of branchial arch I, II and III. During this same 4th week the buccopharyngeal membrane ruptures and, the 4 lingual swellings merge to become the t o n g u e
Fate of 4 lingual swellings during 4th embyronic week:
Position of the 4 lingual swellings along the front wall of the pharynx and their
contributions to the t o n g u e:
Tuberculum Impar and 2 Lateral lingual swellings become anterior two - thirds of tongue
Copula becomes posterior third or root of tongue
Copula becomes
posterior third or root of tongue
The stomodeum will begin to partition
into oral and nasal cavities in the following
6th embryonic week:
Fifth Embryonic Week
Appearance of structures within the stomodeum that enter into formation of palate:
Primary palate: Nasal septum: Palatine folds or shelves:
Primary palate arises from
inner surface of median nasal facial process
Nasal septum arises from
primary palate
Palatine folds arise from
inner surface of maxillary facial processes
Outer surface of median facial process become what parts of face?
Frontal: note vertical position of palatine folds or shelves lateral to tongue
Outer surface of maxillary processes become what parts of face?
Axial
Tongue appears in what embryonic week ?
4th
Primary palate:
inner surface of median nasal process:
median nasal process gives rise to the nasal septum
Palatine folds or shelves: arise from
medial or stomodeal surfaces of maxillary processes
Histologic: Frontal view
Fifth embryonic week
The palatine folds or shelves, that arise from the inner surfaces of the
maxillary processes, are vertical in position on either side of the tongue
The palatine folds or shelves have
lining epithelium that is connected to an underlying
mesenchymal tissue also called ectomesenchyme (originates in ectoderm primary germ layer)
5th week Palatine folds move from a vertical position to a
horizontal position above the tongue: