For medical, nursing and physiotherapy undergraduates, and postgraduates

1. HEAD AND NECK - II
DR. SUNDIP CHARMODE
ASSOCIATE PROFESSOR
DEPARTMENT OF ANATOMY
AIIMS RAJKOT

2. DEVELOPMENT OF FACE
• At the end of the fourth week, Facial Prominences consisting
primarily of neural crest derived mesenchyme and formed mainly by
the first pair of pharyngeal arches appear.
• Maxillary Prominences can be distinguished lateral to the
stomodeum, and
• Mandibular Prominences can be distinguished caudal to this
structure (Fig. 17.21).

4. DEVELOPMENT OF FACE
• The Frontonasal Prominence, formed by proliferation of
mesenchyme ventral to the brain vesicles, constitutes the upper border
of the stomodeum.
• On both sides of the frontonasal prominence, local thickenings of the
surface ectoderm, the nasal (olfactory) placodes, originate under
inductive influence of the ventral portion of the forebrain (Fig. 17.21).

5. DEVELOPMENT OF FACE
• During the fifth week, the nasal placodes
invaginate to form nasal pits.
• In so doing, they create a ridge of tissue
that surrounds each pit and forms the
nasal prominences.
• The prominences on the outer edge of the
pits are the lateral nasal prominences;
those on the inner edge are the medial
nasal prominences (Fig. 17.22).

8. DEVELOPMENT OF FACE
• During the following two weeks, the
maxillary prominences continue to
increase in size.
• Simultaneously, they grow medially,
compressing the medial nasal prominences
toward the midline.
• Subsequently, the cleft between the medial
nasal prominence and the maxillary
prominence is lost, and the two fuse (Fig.
17.23).

9. DEVELOPMENT OF FACE
• Hence, the upper lip is formed by the
two medial nasal prominences and the
two maxillary prominences.
• The lateral nasal prominences do not
participate in formation of the upper lip.
• The lower lip and jaw form from the
mandibular prominences that merge
across the midline.

10. DEVELOPMENT OF
NASOLACRIMAL DUCT
• Initially, the maxillary and lateral nasal prominences
are separated by a deep furrow, the nasolacrimal
groove (Figs. 17.22 and 17.23).
• Ectoderm in the floor of this groove forms a solid
epithelial cord that detaches from the overlying
ectoderm.
• After canalization, the cord forms the nasolacrimal
duct; its upper end widens to form the lacrimal sac.
• Following detachment of the cord, the maxillary and
lateral nasal prominences merge with each other.

11. DEVELOPMENT OF
NASOLACRIMAL DUCT
• The nasolacrimal duct then runs from the medial corner
of the eye to the inferior meatus of the nasal cavity, and
• The maxillary prominences enlarge to form the cheeks
and maxillae.
• The nose is formed from five facial prominences (Fig.
17.23):
• Frontonasal prominence forms bridge
• Merged medial nasal prominences provide the crest
and tip, and
• Lateral nasal prominences form the sides (alae)
(Table 17.3).

12. 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. 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 triangular primary palate (Fig. 17.24).

15. SECONDARY PALATE
• The Inter-maxillary segment is continuous with the rostral portion of the
nasal septum, which is formed by the frontal prominence.
• The Primary Palate is derived from the intermaxillary segment (Fig.
17.24),
• The Main part of the Definitive Palate is formed by two shelflike
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 (Fig. 17.25).

17. SECONDARY PALATE
• In the seventh week,
however, the palatine shelves
ascend to attain a horizontal
position above the tongue and
fuse, forming the secondary
palate (Figs. 17.26 and
17.27).

18. 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 (Fig. 17.27B).
• 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
(Fig. 17.27).

19. DEVELOPMENT OF NASAL CAVITIES
• During the sixth week, the nasal pits
deepen considerably, partly because
of growth of the surrounding nasal
prominences and partly because of
their penetration into the underlying
mesenchyme (Fig. 17.31A).

20. DEVELOPMENT OF NASAL CAVITIES
• At first, the oronasal membrane
separates the pits from the primitive
oral cavity by way of the newly
formed foramina, the primitive
choanae (Fig. 17.31 C).

21. DEVELOPMENT OF NASAL CAVITIES
• These choanae lie on each side of the
midline and immediately behind the
primary palate.
• Later, with formation of the secondary
palate and further development of the
primitive nasal chambers (Fig. 17.31D),
the definitive choanae lie at the junction
of the nasal cavity and the pharynx.

22. DEVELOPMENT OF NASAL CAVITIES
• Paranasal air sinuses develop as diverticula of the lateral nasal wall
and extend into the maxilla, ethmoid, frontal, and sphenoid bones.
• They reach their maximum size during puberty and contribute to the
definitive shape of the face.

24. CLEFT PALATE
• Cleft palate results from a lack of fusion of the palatine shelves, which
may be due to smallness of the shelves, failure of the shelves to
elevate, inhibition of the fusion process itself, or failure of the tongue
to drop from between the shelves because of micrognathia.
• The third category is formed by a combination of clefts lying anterior
as well as posterior to the incisive foramen [Fig. 17.28F].

25. CLEFT PALATE
• Anterior clefts vary in severity from a barely visible defect in the vermilion
of the lip to extension into the nose. In severe cases, the cleft extends to a
deeper level, forming a cleft of the upper jaw, and the maxilla is split
between the lateral incisor and the canine tooth [Fig. 17.29A].
• Frequently, such a cleft extends to the incisive foramen [Fig.17.28C,F].
• Likewise, posterior clefts vary in severity from clefting of the entire
secondary palate [Fig. 17.28E and 17.298] to clefting of the uvula only.

27. OBLIQUE FACIAL
CLEFTS
• Oblique facial clefts are produced
by failure of the maxillary
prominence to merge with its
corresponding lateral nasal
prominence along the line of the
nasolacrimal groove [Fig.
17.23A,C].
• When this occurs, the
nasolacrimal duct is usually
exposed to the surface
[Fig.17.29C].

28. MEDIAN [MIDLINE] CLEFT LIP
• Median [midline] cleft lip, a rare abnormality, is caused by incomplete
merging of the two medial nasal prominences in the midline [Figs.
17.29D and 17.30A,B].
• Infants with midline clefts are often cognitively impaired and may
have brain abnormalities that include varying degrees of loss of
midline structures. Loss of midline tissue may be so extensive that the
lateral ventricles fuse [holoprosencephaly] [Fig. 17.30C].

30. FACTORS AFFECTING CLEFT LIP/CLEFT
PALATE
• These defects are induced very early in development, at the beginning
of neurulation [days 19 to 21] when the midline of the forebrain is
being established.
• Most cases of cleft lip with or without cleft palate are multifactorial.
These conditions are usually classified as cleft lip with or without cleft
palate.
• Cleft Palate thought to be etiologically and pathogenetically distinct.

31. FACTORS AFFECTING CLEFT LIP/CLEFT
PALATE
• Cleft lip with or without cleft palate [approximately 1/700 births]
occurs more frequently in males [65%] than in females, and its
incidence varies among populations.
• Asians and Native Americans have some of the highest rates
[3.5/1,000], whereas African Americans have the lowest [1/1,000].
• The frequency of isolated cleft palate is lower than that of cleft lip
[1/1,500 births], occurs more often in females [55%] than in males.

32. FACTORS AFFECTING CLEFT LIP/CLEFT
PALATE
• In females, the palatal shelves fuse approximately 1 week later than in
males, which may be related to why isolated cleft palate occurs more
frequently in females than in males.
• Causes of cleft lip with or without cleft palate are not well defined.
Some cases are syndromic and associated with certain syndromes and
genes. Others are nonsyndromic but associated with some of the same
genes that cause syndromes, such as IRF6 [van der Woude syndrome]
and MSX1.

33. FACTORS AFFECTING CLEFT LIP/CLEFT
PALATE
• Still, other cases are caused by exposure to teratogenic compounds,
such as anticonvulsant medications, particularly valproic acid.
Cigarette smoking during pregnancy also increases the risk for having
a baby with orofacial clefts.

34. THANK YOU