embryology notes

1. OJORA K.A
DEVELOPMENT OF THE FACE
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2. Development of face
 The facial primordia appear early in the fourth week around the large
primordial stomodeum .
 The five facial primordia that appear as prominences around the
stomodeum are
I. The single frontonasal prominence
II. The paired maxillary prominences(derivatives of the first pair of
pharyngeal arches)
III. The paired mandibular prominences(derivatives of the first pair of
pharyngeal arches)
 The prominences are produced mainly by the expansion of neural crest
populations that originate from the mesencephalic and rostral
rhombencephalic neural folds during the fourth week.
 These cells are the major source of connective tissue components,
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3. 3

4.  The frontonasal prominence (FNP)
surrounds the ventrolateral part of
the forebrain, which gives rise to the
optic vesicles that form the eyes.
 The frontal part of the FNP forms the
forehead; the nasal part of the FNP
forms the rostral boundary of the
stomodeum and nose.
 The paired maxillary prominences
form the lateral boundaries of the
stomodeum, and the paired
mandibular prominences constitute
the caudal boundary of the
stomodeum.
 Facial development occurs mainly
between the fourth and eighth
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5.  By the end of the fourth week, bilateral oval
thickenings of the surface ectoderm-nasal
placodes-the primordia of the nasal
epithelium, have developed on the
inferolateral parts of the FNP.
 Initially these placodes are convex, but later
they are stretched to produce a flat
depression in each placode.
 Mesenchyme in the margins of the
placodes proliferates, producing horseshoe-
shaped elevations-the medial and lateral
nasal prominences.
 As a result, the nasal placodes lie in
depressions-the nasal pits.
 These pits are the primordia of the anterior
nares (nostrils) and nasal cavities.
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6.  Proliferation of mesenchyme in the
maxillary prominences causes them to
enlarge and grow medially toward each
other and the nasal prominences.
 This proliferation-driven expansion
results in movement of the medial
nasal prominences toward the median
plane and each other.
 Each lateral nasal prominence is
separated from the maxillary
prominence by a cleft called the
nasolacrimal groove.
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7.  By the end of the sixth week, each
maxillary prominence has begun to
merge with the lateral nasal
prominence along the line of the
nasolacrimal groove.
 The nasolacrimal duct develops from a
rodlike thickening of ectoderm in the
floor of the nasolacrimal groove.
 This thickening gives rise to a solid
epithelial cord that separates from the
ectoderm and sinks into the
mesenchyme.
 Later, as a result of apoptosis, this
epithelial cord canalizes to form a duct.
 The superior end of this duct expands
to form the lacrimal sac.
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8. INTERMAXILLARY SEGMENT
 As a result of medial growth of the maxillary
prominences, the two medial nasal prominences
merge not only at the surface but also at a deeper
level.
 The structure formed by the two merged
prominences is the intermaxillary segment.
 It is composed of
1. A labial component, which forms the philtrum
of the upper lip;
2. An upper jaw component, which carries the
four incisor teeth; and
3. A palatal component, which forms the
triangular primary palate.
 The intermaxillary segment is continuous with the
rostral portion of the nasal septum, which is formed
by the frontal prominence.
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9. DEVELOPMENT OF LOWER LIP
 The mandibular process of two
sides grow towards each other
and fuse in the midline.
 The fused mandibular
processes give rise to lower
lip& to lower jaw.
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10. DEVELOPMENT OF THE LIP
 After the formation of the upper lip and lower lips the stomatodaeum
becomes broader.
 In its lateral part it is bounded by the maxillary process from above and
mandibular process from below.
 Progressive fusion of both the processes form the cheek.
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11. Summary: Structures Contributing to Formation of the
Face
Prominence Structures Formed
Frontonasal One in number
- Forms: Forehead, bridge of nose, and medial and
lateral nasal prominences
Maxillary (Two) One on each side. Merge with the lateral nasal
process then with the medial nasal process to
form:
-Part of Cheeks, Upper lip except the median part
(Philtrum); Upper Jaw except median part;
Definitive palate
Two Medial nasal (from
frontonasal Process)
-- Two arise from lower border of frontonasal
process; one on each side medially. - Merge with
each other in the middle line to form intermaxillary
segment which will give:
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12. Summary: Structures Contributing to Formation of the
Face
Prominence Structures Formed
Two Lateral nasal (from
frontonasal process)
-Two arise from lower border of
frontonasal process; one on each side
laterally. Separated from the maxillary
process by cleft where the
nasolacrimal duct lies - Give: Alae of
nose
Mandibular (two) One on each side below the maxillary
processes. Merge with its fellow of
other side to form: - Whole Lower lip;
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13. SECONDARY PALATE
 Although the primary palate is derived
from the intermaxillary segment , the main
part of the definitive palate is formed by
two shelf-like outgrowths from the
maxillary prominences.
 These outgrowths, the palatine shelves,
appear in the sixth week of development
and are directed obliquely downward on
each side of the tongue .
 In the seventh week, however, the
palatine shelves ascend to attain a
horizontal position above the tongue and
fuse, forming the secondary palate.
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14. SECONDARY PALATE
 Anteriorly, the shelves fuse with the
triangular primary palate, and the incisive
foramen is the midline landmark between
the primary and secondary palates.
 At the same time as the palatine shelves
fuse, the nasal septum grows down and
joins with the cephalic aspect of the newly
formed palate.
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15. SECONDARY PALATE
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16. CONGENITAL ANOMALIES OF THE FACE
 Macrostomia (large mouth):Due to arrest of fusion between
the maxillary and mandibular processes to shift the angle
medially >>> very big oral fissure.
 Microstomia:Due to excessive fusion between the maxillary
and mandibular processes >>>>very small oral fissure.
 Aganthia: absent lower jaw
 Micrognathia: small lower jaw
 Atresia of nasolacrimal duct: failure of the canalization of
the nasolacrimal duct
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18. Oblique facial cleft:
 Cleft extends from the upper lip to
orbit
 Due to failure of fusion between
maxillary process and lateral margin of
frontonasal process
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19. Cleft Lip and Cleft Palate
 Clefts of the lip and palate are the most common craniofacial
anomalies.
 The defects are usually classified according to developmental
criteria, with the incisive fossa as a reference landmark.
 These clefts are especially conspicuous because they result in an
abnormal facial appearance and defective speech.
 Cleft lip is common among males while cleft palate is more
common among females.
 Unilateral clefts - 80% of the incidence
 Bilateral clefts - remaining 20%.
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20. Anterior cleft anomalies
 Includes cleft lip, with or without cleft
of the alveolar part of the maxilla.
 A complete anterior cleft anomaly is
one in which the cleft extends
through the lip and alveolar part of
the maxilla to the incisive fossa,
separating the anterior and posterior
parts of the palate.
 Anterior cleft anomalies result from
a deficiency of mesenchyme in the
maxillary prominence(s) and the
median palatal process.
E, Complete unilateral cleft of the lip and alveolar
process of the maxilla with a unilateral cleft of the
primary (anterior) palate.
F, Complete bilateral cleft of the lip and alveolar
processes of the maxillae with bilateral cleft of the
anterior part of the palate.
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21. Posterior cleft anomalies
 Includes clefts of the secondary palate
that extend through the soft and hard
regions of the palate to the incisive fossa,
separating the anterior and posterior
parts of the palate.
 Posterior cleft anomalies result from
defective development of the secondary
palate and growth distortions of the
lateral palatal processes, which prevent
their fusion. G, Complete bilateral cleft of the lip and alveolar
processes of the maxillae with bilateral cleft of the
anterior part of the palate and unilateral cleft of the
posterior part of the palate. H, Complete bilateral cleft
of the lip and alveolar processes of the maxillae with
complete bilateral cleft of the anterior and posterior
palate.
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22. A unilateral cleft of the upper lip
 A unilateral cleft of the upper lip results
from failure of the maxillary prominence on
the affected side to unite with the merged
medial nasal prominences.
 This is the consequence of failure of the
mesenchymal masses to merge and the
mesenchyme to proliferate and smooth out
the overlying epithelium.
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23. A bilateral cleft lip
 results from failure of the mesenchymal
masses in both maxillary prominences to
meet and unite with the merged medial
nasal prominences.
 The epithelium in both labial grooves
becomes stretched and breaks down.
 In bilateral cases, the defects may be
dissimilar, with varying degrees of defect
on each side.
 When there is a complete bilateral cleft
of the lip and alveolar part of the maxilla,
the medial palatal process hangs free
and projects anteriorly.
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24. Median cleft of the upper lip
 A median cleft of the upper lip is an
extremely rare defect that results from a
mesenchymal deficiency.
 This defect causes partial or complete
failure of the medial nasal prominences
to merge and form the median palatal
process.
 A median cleft of the upper lip is a
characteristic feature of the Mohr
syndrome, which is transmitted as an
autosomal recessive trait.
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25. Cleft palate
 A cleft palate, with or without a
cleft lip, occurs approximately
once in 2500 births and is more
common in females than in males.
 The cleft may involve only the
uvula; a cleft uvula has a fishtail
appearance, or the cleft may
extend through the soft and hard
regions of the palate.
 In severe cases associated with a
cleft lip, the cleft in the palate
extends through the alveolar part
of the maxilla and the lips on both
sides.
C, Unilateral cleft of the secondary (posterior) palate.
D, Bilateral cleft of the posterior part of the palate.
G, Complete bilateral cleft of the lip and alveolar processes of the
maxillae with bilateral cleft of the anterior part of the palate and unilateral
cleft of the posterior part of the palate.
H, Complete bilateral cleft of the lip and alveolar processes of the
maxillae with complete bilateral cleft of the anterior and posterior palate.
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27. Cleft malformations of face and palate
http://www.rodina.cz/clanek3188.htm
before
before
after
after
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