GENERAL EMBRYO LOGY

1. DEVELOPMENT OF
FACE, PALATE
AND JAWS
Presented by:
DR. PANKAJ GOYAL

2. GROWTH
• Increase in size, change in proportion
and progressive complexity-
Krogman
• An increase in size- Todd
• Change in any morphological parameter
which is measurable- Moss

3. DEVELOPMENT
toward
s
• Development is the
progress maturity- Todd(1931)
• Differentiation is the change from a
generalized cell or tissue to one that is
more specialized. It is change in quality or
kind.

4. INTRODUCTION
• Embryology is the study of the
development of an individual before birth.
• Fertilization is the fusion of male and
female germ cells to form a zygote. It
takes place in the ampulla of the uterine
tube.
• During the first two months the developing
zygote is called an embryo and after that it
is called a fetus.

5. • The human embryo contains 46
chromosomes, called as diploid number.
Out of which 44 chromosomes are
autosomes and remaining 2 are sex
chromosomes, designated as X and Y
chromosomes.
• The sex chromosome in female are XX
chromosome and in male XY
chromosome.

6. CONTENTS
• General embryology
• Pharyngeal arches
• Development of face
• Development of palate
• Development of tongue
• Development of mandible
• Pre natal growth of mandible
• Post natal growth of mandible
• Age changes
• Developmental anomalies

7. Ovulation
• Approximately every month an egg will mature
within one of the ovaries.
• when a mature egg is released from the ovary, pushed
down the fallopian tube, and is available to be fertilized.

8. 2 parts of ovulation cycle
• follicular phase. first half of the cycle, this phase starts
the first day of the last menstrual period (LMP) and
continues until ovulation.
• luteal phase. The second half of the cycle from the day
of ovulation until the next period begins.

9. **ovulation can help a woman get a better idea of when
pregnancy can and cannot occur during her monthly
cycle.

10. THE PROCESS OF FERTILIZATION
• The male gamete (sperm) fuses with
the female gamete (ovum)

11. • Occurs when the sperm successfully enters the
ovum membrane.
• Sperm should be ejaculated during sexual
intercourse (or during artificial insemination)

12. Conception
• Occurs when a female egg (ovum)is penetrated and
fertilized by the male sperm.
• The union of the mother’s and father’s sex cells, also
known as gametes or germ cells.
o Mother’s sex cell areeggs
o Father’s sex cells are sperm
• Successful conception depends on:
o ovaries releasing one healthy egg cell.
o Egg cell migrates most of the way down the fallopian tube.
o One sperm must penetrate the ovum to form a zygote.

13. Stages/Period of Prenatal
Development

14. Stages of Prenatal
development
• Zygotic (or Germinal) Stage 0-2 weeks
• Embryonic Stage 2-8 weeks
• Fetal Stage 9-40 weeks

15. Zygotic/Germinal Period
• Begins when egg is fertilized in the fallopian tube
• Period of rapid cell division
• Ends 2 weeks later when the zygote is implanted in
the wall of the uterus

16. Developmental Process
• The zygote is transformed into an embryo and then a
fetus through the process of:
o Cell Division- begins 12 hours after fertilization and continues throughout fetal
development.
o Cell migration- cell move from point of origin to elsewhere in the embryo
o Cell differentiation- cells begin to specialize, fulfilling the needs of
separate bodily structures and functions.
o Cell death- the selective death of certain cells as they are no longer
needed

17. Key terms
• Zygote- The genetic material of the sperm and egg
combine to form a single cell.
o Union of sperm and egg cell.
• Cleavage- process of rapid division of zygote.
• Blastomeres- first two identical cell.
• Morula- sixty hours after fertilization, approximately
sixteen cells have formed, still enclosed by the zona
pellucida

18. • Blastocoele- a fluid-filled cavity that forms in the
center of the group of cells.
• Trophoblasts-outer shell of cell
• Embryoblasts- inner mass of cells.
• Blastocyst- previously morula, when zona pellucida
disappeares
**at this stage the blastocyst consists of 200-300 cells
and is ready for implantation.

20. • Implantation- the process in which the blastocyst
implants to the uterine wall, occurs approximately six
days after conception.
• The blastocyst first adheres to the wall then moves
into the uterine tissue.
• Implantation marks the end of the germinal stage and
the beginning of the embryonic stage.
Chapter II- Child and Adolescent Period

21. Embryonic Stage
Chapter II- Child and Adolescent Period
• From 2 to 8 weeks after conception
• Begins after implantation and last until eight weeks
after conception
• Cell differentiation intensifies
• Life support systems for the embryo develop
• Organs Appear

22. Germ layers
Chapter II- Child and Adolescent Period
• Ectoderm (outer layer)-develops skin, hair, nails,
sense organs, nervous tissue
• Mesoderm (middle layer)-develops muscles, bones,
circulatory system, lymph system, kidneys, gonads
• Endoderm (inner layer)-develops pharynx, tonsils,
thyroid, trachea, lungs, digestive system, bladder,
urethra

23. Neural Crest cells
• A group of cells separate from the neuroectoderm
on the lateral aspect of the neural plate.
• Undergo epithelial-mesenchymal interactions.
• BMP and FGF are the inducing agents.
• Embryonic CT derived from mesoderm-
mesenchyme
• Head- neuroectoderm- ectomesenchyme
• Form all tissues of tooth except enamel.
• Treacher Collins syndrome.

24. Folding of the Embryo
• In 2 planes:
rostrocaudal axis
and lateral axis.
• Head fold critical in
formation of oral cavity.
• Stomatodeum
separated from
the gut by
the
buccopharyngeal

41. PHARYNGEAL ARCHES
• Rod-like thickenings of mesoderm in the foregut.
• At first 6 arches. 5th arch disappear, only 5 remains.
• The ventral ends of the arches of the right and left
sides meet at the middle line in the floor of the
pharynx.
• They bring about elongation of the region between the
stomatodeum and the pericardium forming neck.
• In the interval between any two adjoining arches,
endoderm extends outwards to form a series of
pouches. They are called endodermal or pharyngeal

59. ARC
H
NERVE OF
THE
ARCH
DERIVATIV
ES
First
(mandibula
r arch)
Mandibula
r
Muscles of mastication, anterior belly of
digastric, tensor tympani, tensor palati,
meckels cartilage, sphenomandibular
ligament, anterior ligament of malleus.
Second
(hyoid
arch)
Faci
al
Stapes, styloid process, stylohyoid
ligament, smaller cornu of hyoid bone,
superior part of body of hyoid bone,
occipitofrontalis, platysma, posterior belly
of digastric, auricular muscle .
Thir
d
Glosso-
pharyngeal
Stylopharyngeus, greater cornu of hyoid
bone, lower part of hyoid bone.
Fourt
h
Superior
laryngeal
Muscles of larynx and
pharynx.
Fift
h
Recurrent
laryngeal

60. Fate of endodermal
pouches• 1st pouch: ventral part obliterated
by formation of tongue.
dorsal part – tubotympanic recess
proximal – auditory tube, middle ear
cavity, tympanic antrum.
• 2nd pouch: tonsil, tubotympanic recess,
• 3rd pouch: inferior parathyroid glands,
thymus.
• 4th pouch: superior parathyroid
glands, thyroid glands
• 5th pouch: ultimobranchial body.

61. DEVELOPMENT OF FACE
• The basic morphology of the face is created 24th
and 38th day of gestation - development & fusion
of the prominences:-
process &
mandibular
– Frontonasal
prominence
– The first pharyngeal (
or Mandibular) arch
on each side.
• At 24 days,

62.  At this stage each mandibular arch forms the lateral wall of
stomatodaeum. This arch gives off a bud from its dorsal end. This bud is
called the maxillary process. It grows ventro-medially cranial to the main
part of the arch which is now called the mandibular process.
 Early development is dominated by proliferation and migration of
ectomesenchyme involved in the formation of primitive nasal cavities.
 At about 28 days, localized thickening develop
within ectoderm of the frontal prominence, just rostral to
the opening of the stomatodaeum. This thickenings are called olfactory or
nasal placodes.
Rapid proliferation of mesenchyme - Horse
shoe shaped ridge - nasal pits.

63. • Lateral arm of
and middle arm -
medial
horse shoe - lateral
nasal
nasal
proces
s
proses
s.
• Region
of frontal prominence where
nosedevelop - frontonasal process.
• The median nasal processes of both sides,
together with the frontonasal process, give
rise to the middle portion of the nose,
middle portion of the upper lip, anterior
portion of maxilla and the primary palate.

64. Maxillary process grows
approaches the lateral
and
mediall
y
medial
an
d
nas
al
processes but remains separated from them
by distinct groove- naso-optic and
bucconasal groove.
Maxillary processes grow medially -
pushing the medial nasal process towards
midline and merges anatomic counterpart.

65. Developmental anomalies of the
face• Harelip
• Oblique facial cleft
• Macrostomia
• Lateral facial cleft
• Retrognathia
• Agnathia
• Mandibulofacial dysostosis
• Hypertelorism
• Congenital pits and fissure on
lips
• proboscis

66. OBLIQUE FACIAL
CLEFT
HAREL
IP
PROBOS

67. Developmental anomalies
of lips and palate
• Congenital lips
• Commissural pits and
fistulas
• Van der woude syndrome
• Cleft lip and cleft palate
• Chelitis glandularis
• Chelitis granulomatosa

68. Cleft lip and cleft Palate

70. Anomalies of tongue
• Macroglossia, microglossia,
aglossia
• Bifid tongue
• Ankyloglossia
• Persistence of tuberculum impar
• Thyroid tissue within the
muscles
• Remnants of thyroglossal duct
• Fissured tongue

71. The Mandible
(Growth AndDevelopment)

72. Anatomy of the mandible
It has horseshoe shaped
body which lodges the
teeth, and pair of rami
which project upwards
from the posterior ends of
the body and provide
attachment to muscle.
8 dec 202072

73. The body:
Body has outer and inner surfaces and upper and
lower border.
The ramus:
Quadrilateral in shape, has two surfaces, lateral
and medial, four borders and the coronoid and
condyloid process.
8 dec 202073

74. LATERAL SURFACE PRESENTS THE FOLLOWING
FEATURES
69
1. Symphisis menti
2. Mental foramen
3. Mental protuberance
4. Mental tubercle
5. The oblique line
6. Condylar process
7. Coronoid process
8. Mandibular notch
9. Alveolar process
8 dec 2020

75. The Medial surface presents the following features
1. Mental spine
2. Mylohyoid line
3. Submandibular
fossa
4. Sublingual fossa
5. Mylohyoid
groove
6. Mandibular
foramen
70 8 dec 2020

76. (Gray’s Anatomy – Fortieth edition)
8 dec 202076

77. MUSCULAT ATTACHMENT TO THE MANDIBLE

78. PRENATAL DEVELOPMENT OF
MANDIBLE
9
Start abouth 4th week of intara-
uterine life.
Developing forebrain and the
pericardium form two prominent
bulges on the ventral aspect of
the embryo.
These bulges are separated by
primitive oral cavity or
stomodaeum
The stomodaeum is lined by
ectoderm and is separated from
the anterior end of foregut by the
bucco-pharyngeal membrane.
8 dec 2020

79. 10
Lateral view of embryo showing the formation of
pharyngeal arches between stomatodaeum and
the pericardial bulge
8 dec 2020

80. 11
Coronal section through cranial part of foregut
before formation of pharyngeal arches.
(Human embryology- Inderbir Sing Eight 2e9dJiutiloyn2)014

81. 12
Formation of pharyngeal arches
(Human embryology- Inderbir Sing Eight edition2
)9July 2014

82. First Branchial arch called MANDIBULARARCH.
Mandibular arch gives off a bud from its dorsal
end called maxillary process.
It grows ventro-medially cranial to main part of
the arch which is called mandibular process.
8 dec 202082

83. Mandibular process of each side grow towards
each other.
fuse in midline give rise to mandible.
First structure develop in lower jaw :
- Mandibular division of Trigeminal nerve.
- Neurotrophic factor produced by nerve
8 dec 202083
induce osteogenesis.
(Ten Cate’s Oral Histology – Sixth Edition)

84. MECKEL'S CARTILAGE
It is the cartilage of the first arch
In human beings the Meckel's cartilage has a
close positional relationship to the developing
mandible but makes no contribution to it.
At 6 weeks of development this cartilage extends
as a solid hyaline cartilaginous rod, surrounded
by a fibrocellular capsule, from the developing ear
region to the midline of the fused mandibular
processes.
8 dec 202084

85. The Mandibular branch of trigeminal nerve has
close relationship to Meckel’s cartilage
8 dec 202085

86. On lateral aspect of Meckel’s cartilage, during the
6th week of embryonic development, a condensation
of mesenchyme occurs in the angle formed by the
division of the inferior alveolar nerve and its incisor
and mental branches.
(Ten Cate’s Oral Histology – Sixth Edition) 8 dec 202086

87. Centre of ossification
Intramembraneou
s Ossification
starts at the
division of mental
and incisive
branch of inferior
alveolar nerve
lateral to meckel’s
cartilage around
7th week IUL.
18 8 dec 2020

88. 19
Fromcenter of ossification bone formation spreads:
Anteriorly - midline
Posteriorly - where mandibular nerve divided into
lingual and inferior alveolar branch.
Bone formation spreads rapidly and surrounds the inferior
alveolar nerve to form mandibular canal.
Intra-membranous ossification spreads in anterior and posterior
direction forms the Body & Ramus of the mandible.
8 dec 2020
Gray’s Anatomy – Fortieth edition

89. Anteriorly bone extends towards midline and comes
in approximation with similar bone forming on
opposite side.
These two bones remain separated by fibrous tissue
mental symphysis untill shortly after birth.
Continued bone formation increases size of
mandible with development of alveolar process to
surround the developing tooth germ.
8 dec 202089

90. .
Ossification spread
posteriorly to form
ramus of mandible,
turning away from
meckel’s cartilage.
This point of
divergence is
marked by lingula in
adult mandible.
8 dec 202090

91. Thus by 10 weeks the rudimentary mandible is
formed almost entirely by membranous
ossification with little direct involvement of
Meckel’s cartilage
8 dec 202091
(Ten Cate’s Oral Histology – Sixth Edition)

92. NOW….. What is the
fate of the Meckel’s
cartilage?
8 dec 202092

93. Incus and malleus
Spine of sphenoid bone
Anterior ligament of malleus
Spheno-mandibular ligament
8 dec 202093

94. SECONDARY CARTILAGES IN
MANDIBULAR DEVELOPMENT
Further growth until birth influenced by appearance
of secondary cartilage
Condylar cartilage:
Coronoid cartilage:
Symphyseal cartilage:
8 dec 202094

95. CONDYLAR CARTILAGE
appear during 12th week of IUL
Rapidly form cone shape mass which is
converted quickly to bone by endochondral
ossification.
At the end of 20th week only a thin layer remains
on the condylar head ,persist until the end of the
second decade of life ,providing a further growth
(Ten Cate’s Oral Histology – Sixth Edition)
8 dec 202095

96. • Cartilage fuses with mandibular ramus around 4th month.
(Contemporary orthodontics Williams R. proffit fifth edition
8 dec 202096

97. CORONOID CARTILAGE
Appears at about 4 month of development.
Coronoid cartilage is transient growth cartilage
and disappears long before birth.
Cartilage grow as a response of developing
temporalis muscle.
Coronoid cartilage become incorporated into
expanding intra-membranous bone of ramus.
8 dec 202097
(Ten Cate’s Oral Histology – Sixth Edition)

98. SYMPHYSEAL CARTILAGE
Two in number
Appear in between the two end of Meckel’s
cartilage.
They are obliterated within the first year after
birth.
8 dec 202098
(Ten Cate’s Oral Histology – Sixth Edition)

100. Growth of mandible
Growth of the mandible was thought to occur principally
by growth at condyle.
Superior and posterior growth of condyle presses
against the glenoid fossa/ cranial base which provides
an anterior thrust to displace the lower jaw forward.

101. Ranly explains the concept with the example of a man
swimming
In this the legs are pressed against the wall of
swimming pool.
This pressure gives a thrust to the swimmer to surge
forward

102. The concept of posterior growth and anterior
displacement leads to primary displacement
But according to Moss the expansion of the orofacial
capsule leads to passive displacement of mandible with
secondary adaptive growth in the condyle.
There is also a definitive increase in arch length by
ramal remodeling posteriorly to maintain condylar
contact with temporal fossa

103. Ramus
The earliest concept of corpus
lengthening stated that there is
resorption at the anterior border of
ramus and deposition at the posterior
border so that ramus is shifted to a
more posterior location and corpus
lengthened.
This the Hunterian Concept.
But later it was found that the
mandible undergoes a rotational
pattern of growth.

104. The remodeling of ramus occurs in an arcial pattern.
The ramal angle of childhood slightly uprights in
adolescence and in late adulthood, it becomes acute

105. Ramal Uprighting
Direction of deposition &
resorption reverses
Inferior part of anterior margin
is resorptive whereas superior
portion is depository.
While the inferior portion of
posterior border is depository
and superior portion is
resorptive

106. There is not only change in angulation of ramus but
there is also an increase in vertical height of ramus.
On the whole, the ramus appears to have rotated
around an arc.

107. With the remodeling of ramus
posteriorly, the mandibular
foramen maintains its position
by deposition in the anterior
rim and resorption in the
posterior rim ie. shifts
posteriorly.

108. Coronoid process
As described by Enlow,
coronoid process has a
propeller like twist.
The medial surface of the
process faces posteriorly,
superiorly and lingually all
at one time
It follows the Enlow’s
expanding V principal.

109. The coronoid process grows and moves cephalically, posteriorly, and
lingually as pictured in these diagrams

110. Periosteal deposition (+) on the lingual surface of the coronoid
process together with removal (—) from the buccal surface

111. The coronoid process of the younger (smaller)
mandible occupies the same level as the lingual
tuberosity in the older growth stage

112. Body of mandible
The corpus or body of
mandible is depository on the
outer surface and resorptive
on the inferior aspect of the
medial surface
The superior aspect of the
medial surface just below the
teeth is depository
In the ramus, remodeling on
the medial surface of ramus
follows the same pattern as

114. Increase in height of alveolar bone accompanies
eruption of teeth
Similar to maxilla, mandibular width completes first,
followed by depth and height.
Lower border of mandible is depository except at the
antegonial notch.

115. Chin
Growth of the chin occurs at
puberty as age advances
Chin becomes prominent at
puberty by selective remodeling
The remodelling pattern of chin
tries to accentuate its
prominence.
There is deposition on the chin ie
mental protrubrance, itself while
the area of anterior surface of
alveolus above the chin is

116. There is corresponding
deposition in the
endosteal surface.
The lingual periosteum
of the symphysis is
depository.

117. Condyle
The cartilaginous covering on the condyle serves a
dual function: it represents an articular cartilage and it
also functions as a growth cartilage
Superior surface of condyle is depository.
Interstitial and appositional growth in this plate produce
a linear movement of the condyle in an obliquely
upward and backward direction.
The Cap of condyle undergoes endochondral
ossification, the rest of the condyle and the neck of
condyle grows by intramembranous ossification.

118. The condyle grows like an expanding V

119. As the ramus elongates, former levels occupied
by the head are remodelled into the upper neck.
With each successive addition of new bone at the
free end of the condyle, all the levels down the
line in the neck and ramus necessarily receive
relocation in their relative position
The condylar head is much broader than the neck
beneath it.
Because the neck is sequentially derived from the
head by remodeling, a marked reduction in width
takes place.
Resorption of the condylar neck on the periosteal
side is accompanied by deposition on the
endosteal surface.

120. The neck of condyle is resorptive on the buccal
and lingual surfaces and this, coupled with
deposition on the condylar head, contributes to
the V configuration.

121. The buccal and lingual surfaces of the neck are equally resorptive
throughout; the inferiorly facing end of buccal surface and
superiorly facing end of lingual surfaces are depository

122. Condylar cartilage is not a primary cartilage but just a
secondary cartilage.
According to Petrovic, the secondary cartilage is more
open to external forces.
In the secondary cartilages like condyle, the zone of
growth contains proliferative cells like skeletoblasts and
prechondroblasts.
The cells of the this zone are just surrounded by type I
collagen unlike in primary cartilage where the cells are
surrounded by cartilaginous matrix.
These cells are exposed to the environment and are
moldable to external influences.

123. This is used to advantage in functional treatment.
The cells of condylar cartilage are not arranged in
rows as it is in primary cartilages.
The condylar cartilage has multidirectional proliferative
capacity.
The condyle can remodel superiorly and posteriorly at
the same time.

124. Lingual Tuberosity
Lingual tuberosity is a very important anatomic site
in mandible at the junction of corpus and ramus at
the medial aspect.
Lingual tuberosity is the counterpart of maxillary
tuberosity.
It not only faces posterior but also is oriented
towards the midline than the ramus.
If viewed from the occlusal aspect, lingual tuberosity
appears to be in line with the dental arch whereas
ramus is slightly away along the arms of the
expanding V.

125. The region below lingual tuberosity is resorptive
thereby accentuating the prominence of tuberosity.

126. When juvenile and adult mandibles are compared with
the view from occlusal surface, the tuberosity is greatly
relocated in a posterior direction.

127. The mediolateral growth lingual tuberosity is meager
when compared to the posterior shift.
Enlow points out that it is due to the stable bicondylar
width established early in childhood.
Bicondylar width in turn is related to the width of the
cranial base that completes early.

128. Antegonial notch
A single field of surface
resorption is present on the
inferior edge of mandible at the
ramus corpus junction. This
forms the antegonial notch
In vertical growth it is deep and
horizontal growth it is shallow.

129. Angle of mandible
Buccal surface
Bone deposition - postero-inferior surface
Bone resorption - antero-superior surface
Lingual surface
Bone deposition – antero-superior surface
Bone resorption – postero-inferior surface

130. Alveolar process
Alveolar growth occurs around tooth buds.
As the teeth develops and begin to erupt , alveolar
process increases in size and height.
Continued growth of alveolar bone increases height of
mandibular body.

131. AGE CHANGES IN THE
MANDIBLE

132. At birth
At the birth the mental foramen,
opens below the sockets for the
two deciduous molar teeth near the
lower border.
The mandibular canal runs near the
lower border.
The gonial angle is obtuse.
It is 175.

133. At Childhood
The two halves of the mandible
fuse during the first year of the
life.
The body becomes elongated in
its whole length, but more
especially behind the mental
foramen, to provide space for
the additional teeth developed in
this part.
Mandibular foramen lies slightly
above the occlusal plane

134. In adult
The mental foramen opens
midway between the upper
and lower borders.
The mandibular canal runs
parallel with the mylohyoid
line.
Mandibular foramen 7 mm
above the occlusal plane
The gonial angle reduces to
about 110 or 120 degrees.

135. In old age
Alveolar border is
resorbed, so that height of
the body is markedly
reduced.
The mental foramen and
mandibular canal are
close to the alveolar
border.
The gonial angle again
becomes obtuse about
140 degrees .

137. Defects of Mandible

138. Micrognathia
Small jaw.
Either the maxilla or the
mandible may be affected.
Can be congenital or acquired.
Characterized by severe
retrusion of chin , a steep
mandibular plane angle.

139. Macrognathia
Abnormally large jaw
May be associated with conditions such as:
Paget’s disease of bone
Acromegaly
Fibrous dysplasia

140. Cherubism
It is benign herditary condition of
maxilla and /or mandible
usually found in children by 5
years of age.
Autosomal dominant inheritance.
Mandible angle, ascending
ramus, retromolar region and
posterior maxilla are most
commonly affected.
Patients typically have a painless

141. CORONOID HYPERPLASIA
Rare developmental anomaly
Results in limited mandibular movement
Unknown etiology.
M:F ratio 5:1
May be unilateral or bilateral
Bilateral is more common

142. CONDYLAR HYPERPLASIA
Excessive growth of one of the condyles
Cause is unknown, but local circulating problems,
endocrine disturbances, and trauma have been
suggested as possible etiologic factors.

143. CONDYLAR HYPOPLASIA
Congenital or acquired
Congenital:
Mandibulofacial dysostosis
Goldenhar syndrome
Hemifacial microsomia
Acquired:
disturbances of the growth center of the condyle

144. TORUS MANDIBULARIS
Develops along the lingual aspect of the mandible.
Probably multifactorial, including both genetics and
environmental influences.

145. BIFID CONDYLE
Rare
Mostly medial and lateral
head divided by an antero
posterior groove.
Some condyles may be
divided into an anterior and
posterior head
Cause is uncertain
Antero-posterior may be
traumatic origin.