4. 1. Period of ovum
Extends
Time of Fertilization Two weeks
During this period
The Cleavage of the Ovum
The Attachment of the Ovum to the Intra-uterine Wall
Occurs
5. 1-7 wks2. Period of embryo
Extends
Fourteen day Fifty sixth day
of intra-uterine life
The major part of the development of the facial &
cranial region occurs
During this period
6. 3. Period of fetus
Extends
Till birthFifty sixth day
During this period
Accelerated growth of the cranio-facial structures
resulting in an increase in their size
Change in proportion b/w the various structures also occurs
In addition
10. • Thus a capsule is formed
around the brain called
Ectomenix or
Ectomeningeal capsule
Mesenchymal tissue condense
around the developing brain
CARTILAGE
40th day
BONE
Chondro-ossification
11. Flexure of the cranial baseالتواء
During the embryonic & early fetal period
in the region
b/w
Pituitary fossa
&
Spheno-occipital junction
cranial base flexed
12. Flexure of the cranial base
accompanied by a corresponding
Flexure of the developing Brain Stem
cranial base flexed
Spinal chord & Foramen magnum
directed
downwards
during the early stages of development
directed backwards
13. Flexure of the cranial base
• Downwards directed foramen
magnum is an adaptation seen
in man who, unlike animals,
(1) Stand erect
• Another consequence of the
flexure is
(2) The predominant downward
rather than forward
displacement of the face
during its growth from the cranial
base
14. PRENATAL GROWTH OF FACIAL SKELETON
– PRENATAL GROWTH OF MAXILLA
– PRENATAL GROWTH OF MANDIBLE
15. on the ventral aspect of the embryo
Ventral aspect Dorsal aspect
About the 4th week of intra-uterine life
(1) the developing brain
Two prominent
BULGES انتفاخ
(2)
20. Mid-sagittal section
BRAIN
HEART
I II
CORD
CARDIAC
BULGE
Full-face view 4-w embryo
Each of these arches contain:
1. A central cartilage rod that forms the skeleton of the arch
2. A muscular component termed as branchiomere
3. A vascular component
4. A neural element
I
II
Branchial arches
21. Mid-sagittal section
BRAIN
HEART
I II
CORD
CARDIAC
BULGE
Full-face view 4-w embryo
The other arches do not have any specific names
I
II
Branchial arches
first arch
MANDIBULAR ARCH
Development of
the naso-maxillary
region
Plays an
important role in
Second arch,
HYOID ARCH.
23. Mid-sagittal section of 1-m embryo
FRONTONASAL
PROCESS
STOMODEUM
BRAIN
PHARYNGEAL ARCHES
I II
The Mesoderm covering the developing forebrain Proliferates & forms a
downward projection that Overlaps the upper part of STOMODEUM.
This downward projection is called
FRONTO-NASAL PROCESS
24. MAXILLARY PROCESS
STOMODEUM
with perforating membrane
CARDIAC
BULGE
MANDIBULAR ARCH
HYOID ARCH
4-w/3.5mm EMBRYO
• The mandibular arch
gives off a bud from its
dorsal end called the
maxillary process
25. MAXILLARY PROCESS
MANDIBULAR PROCESS
CARDIAC
BULGE
HYOID ARCH
STOMODEUM
with perforating membrane
4-w/3.5mm EMBRYO
• The Maxillary Process
GROWS
Ventro-medio-cranial
to the main part of
the Mandibular Arch
which is now called
the Mandibular Process
26. FRONTONASAL PROCESS
MAXILLARY PROCESS
MANDIBULAR PROCESS
CARDIAC
BULGE
HYOID ARCH
STOMODEUM
with perforating membrane
4-w/3.5mm EMBRYO
At this stage the Primitive Mouth or
Stomodeum
OVERLAPPED
from above
from below
on either side
MAXILLARY PROCESS
27. OPTIC PLACODE
CARDIAC BULGE
Bilateral localized thickenings
above the stomodeum
4-w/3.5mm EMBRYO
NASAL PLACODES
soon sink & form
NASAL PITS
The ectoderm overlying the
fronto-nasal process
shows
28. CARDIAC BULGE
The formation of these NASAL PITS
divides the fronto-nasal process
into two parts:
a. The medial nasal process &
b. The lateral nasal process
Lateral processes will
become Alae of Nose
Medial processes form midline nose &
contribute to lip, central upper jaw
& primary palate
4-w/3.5mm EMBRYO
29. 5.5-w/9mm EMBRYO
MAXILLARY PROCESS
As the Maxillary Process
undergoes Growth,
The fronto-nasal process
becomes narrow
so that the two NASAL PITS
come closer
Fronto-nasal process
31. NARIS
Development of palate
• The palate is formed by
contribution of the :
a. Fronto-nasal process
b. Maxillary process
c. Palatal shelves given off
by the maxillary process
NARIS
INTER-MAXILLARY
SEGMENT
PRIMARY PALATE/ Median palatine process
NARIS
Gives rise to the premaxillary
region
Form the rest of the palate
32. Development of palate
• As the PALATAL SHELVES
grow medially,
Their union is prevented by the
presence of the TONGUE
TONGUE
33. Development of palate
• Initially the developing
PALATAL SHELVES grow
vertically downward towards
the floor of the mouth
• During the seventh week of
intra-uterine life,
a transformation in the position of
the palatal shelves occurs
EYE
BRAIN
MECKEL’S CARTILAGE
TONGUE
34. *
Site for meeting and fusion of nasal septum
& palatal shelves
EYE
TOOTH BUD
BRAIN
TONGUE
*
They change from a VERTICAL to HORIZONTAL
position
MECKEL’S CARTILAGE
mandibular bone
TONGUE
LATERAL PALATINE SHELF
Maxillary bone
This transformation is
believed to take place
within hours
35. Reasons to explain how this transformation occurs
a. Alteration in biochemical &
physical consistency of the
connective tissue of the palatal
shelves
b. Alteration in vasculature & blood
supply of the palatal shelves
c. Appearance of intrinsic shelf
force
d. Rapid differential mitotic activity
e. Muscular movements
f. Withdrawal of the embryonic face from
against the heart prominence results in
slight jaw opening. This results in
withdrawal of the tongue from b/w the
palatal shelves from a vertical to a
horizontal position
36. PALATE
PROXIMITY
Epithelial disintegration
& conversion
Mesenchymal continuity
FUSION
Epithelial & Mesenchymal
differentiation
STEPS IN PALATAL-NASAL FUSION
by 8 ½ weeks of intra-uterine life
The connective tissue intermingle
separates the two
nasal cavities from
each other & the oral
cavity
The mesial edges of the
palatal processes fuse with
the free lower end of nasal
septum
38. • The Meckel’s cartilage is derived
from the first branchial arch around
the 41st – 45th day of intra-uterine
life
• It extends from the cartilaginous
otic capsule to the midline or
symphysis & provides a template
for guiding the growth of the
mandible
TONGUE
Meckel’s cartilage
39. TONGUE
Meckel’s cartilage
• A major portion of the Meckel’s
cartilage DISAPPEARS during
growth &
the remaining part develops into the
following structures:
1. The mental ossicles
2. Incus & Malleus
3. Anterior ligament of malleus
4. Spheno-mandibular ligament
TONGUE
40. Meckel’s cartilage
• The first structures to develop in the
PRIMORDIUM of the lower jaw is
THE MANDIBULAR DIVISION of the
trigeminal nerve.
• This is followed by the mesenchymal
condensation forming The first
branchial arch
TONGUETONGUE
43. TONGUE
Neurotrophic factors
OSTEOGENESIS
Ossification centers
induce
Nerve
single
6th week of intra-uterine life
BIFURCATION of the inferior
alveolar nerve into mental &
incisive branches
Intramembranous ossification spreads:
(1) Below & around the inferior alveolar
nerve & its incisive branch & upwards
Trough
(2) Dorsally & ventrally froms the body & ramus of the
mandible
