3. Origin of Facial tissues:
Fertilized ovum - gives rise by series of cell
divisions to Morula.
Morula consists of - Extra embryonic
membranes & Placenta.
Single layer of cells live up to form Embryonic
disc.
Embryonic Disc - by Cell divisions & movements
gives rise to two layered structure with an
intervening space - Upper layer & Lower layers.
Cells of upper layer multiply and migrate &
Occupy the space 3 layers called Germ Layers
Ectoderm, Mesoderm & Endoderm.
4. Neural plate :
The median strip of mesodermal cells induce
its formation within the ectoderm.
Induction :
- Process that initiates differentiation of
cells.
- After induction cells are independent of
further growth.
- Neural plate further grows and folds itself
into the Neural tube.
- Ectodermal cells at the lateral margins of
neural plate - form the neural crest cells.
5. Significance of Neural crest cells :
Neural crest cells are also referred to as
the Ectomesenchymal cells.
(Loose embryonic connective tissue)
By extensive Migrations - Form a variety of
cells which form components of different
tissues.
- Form mesenchyme of upper facial region.
- Neural crest cells migrate to the trunk to
form the neural, endocrine & pigment
cells.
6. Neural Crest Cells In Head & Neck :
- Contribute to skeletal and connective tissues in
Cartilage, Bone, Dentine & Dermis – except
enamel.
- Contribution of Neural crest cells is so extensive
and significant that it is considered as the
fourth germ layer.
- Proper migration of neural crest cells is
important for the development of face and
teeth.
- Once migration is complete, then
vascularization of the mesenchymal tissue
occurs.
7. Vascularization :
- Capillary endothelial cells from
mesodermal cells invade the
mesenchymal tissue.
- Supporting tissues and cells of blood
vessels are derived from mesenchyme.
8. Development of Facial Prominence :
Once the migrated mesenchymal
cells are vascularized a series of
outgrowths called
Facial prominences
are formed which mark the
initiation of facial tissues.
9. 377
4th Week I.U
Facial Processes
A - Frontonasal Process
B - Mandibular
Processes
C – Maxillary Processes
D – Pericardial Swelling
10.
11. Stomodeum:
The primitive Oral Cavity – at this stage
is bounded:
–Laterally by the Maxillary Processes.
–Superiorly by the Frontonasal
process.
–Inferiorly by the Mandibular
processes.
–Posteriorly by the Buccopharyngeal
membrane – separating from the
Endodermally lined Pharynx.
12. Optic & Olfactory Placodes :
- Ectodermal thickenings.
- Medial ones - Olfactory Placodes
- Lateral ones – Optic Placodes
- Surface ectoderm lying apposed to
the developing forebrain undergoes
proliferation by influence of the
forebrain and gives rise to the Lens
of the eye.
- Inner epithelium-Olfactory epithelium
13. 378 5th Week I.U
A – Optic Placode
B – Nasal Placode
C – Medial Nasal
Process
D – Lateral Nasal
Process
E – Maxillary Process
F – Mandibular
Process
G – IInd Branchial Arch
14.
15. Frontonasal region :
- Refers to the crest mesenchyme underlying the
future olfactory placodes located between
the eyes.
- Under the direction of the olfactory placodes
new outgrowths develop on either side of the
olfactory placodes:
Median Nasal process
Lateral Nasal process
- The medial and lateral nasal processes meet
each other below the developing Nasal pit
- The medial and lateral nasal processes and the
olfactory placodes develop and fuse -
contributing to the formation of Primary palate.
16. 379Developing Oral & Nasal
cavities
A – Nasal cavity
B – Oral Cavity
C – Nasal Fin
D – Bucco Nasal
membrane
E – Maxillary Isthmus
17. 380 6th Week of I.U
A – Fused Mandibular
Processes.
B – Maxillary Process.
C – Lateral nasal
Process.
D – Median Nasal Proces.
E – Naso Optic furrow.
18.
19. Primary Palate :
- The Nasal Pits deepen & develop into Nasal
cavities – separated by the primitive Nasal
Septum.
- The primitive Nasal Cavities are separated
from the oral cavity by Primary Palate.
- Forms roof of anterior portion of primitive oral
cavity.
- Separates oral cavity & nasal cavity.
- Contributes to Upper lip, Anterior maxilla &
Maxillary Prominence & Secondary palate.
- At this stage the Stomodeum is in 2 parts:
- Small oral Cavity – below the Primary
Palate.
- Large Oronasal Cavity.
Development of Palate
20. 382 6th week of I.U: Primary
Palate
A – Primitive Nasal
Cavities
B – Primary Nasal
Septum
C – Primary Palate
21. Secondary Palate
- Out growths from the medial portions of
the maxillary process & the Primary
Palate grow to form the Palatine Shelves
of the secondary palate.
- These shelves are brought to a horizontal
position by a rotational hinge like
movement.
- The Secondary Nasal Septum grows
downwards & Posteriorly from the Primary
Nasal Septum in the midline.
22. 383 6th Week I.U – Secondary
Palate
A – Lateral Palatine
Shelves.
B – Primary Palate.
C – Secondary Nasal
Septum.
23.
24. 384 7th Week of I.U – Sec. Palate
A – Lateral Palatine
Shelves.
B – Developing
Tongue
25. Initially the developing Tongue fills the whole
of the Oronasal cavity.
The growing Lateral Paplatine shelves grow
downward and laterally to the Tongue.
26. The Stomodeum enlarges.
Vertically inclined Palatine shelves grow
horizontally.
Later with faster growth & expansion of the
Mandibular arch the Tongue drops down –
allowing the Lateral Palatine Shelves to grow
medially towards each other in the midline to fuse.
The fused Palatine shelves develop the
Secondary Palate.
Behind the Sec. Nasal Septum the Palatine
shelves fuse to form the Soft palate
Secondary palate gives rise to: 2/3 of hard
palate & all of the soft palate.
27. 386
A – Lateral palatine
shelves.
B – Secondary Nasal
Septum.
C – Separating
epithelium.
D – Developing
Maxilla.
28. Mechanisms Involved in Movement
of
Palatine Shelves
1. Rapid differential Mitotic growth.
2. Variations in blood flow.
3. Intrinsic shelf force.
4. Biochemical changes in the connective
tissue.
5. Reflex Jaw activity.
6. Pressure differences between the Oral &
Nasal cavities.
29. 385 8th Week of I.U
A – Lateral Palatine
shelves.
B – Primary Palate.
30. Ossification of Hard Palate
From Four centres:
One in each developing Maxilla –
approximately above the developing
deciduous Canine tooth Germ.
One in each developing Palatine bone –
situated in the region forming the future
perpendicular plate.
31. 387 Early Ossification of Hard
Palate
A – Body of the
Maxilla.
B – Bone extending
into Palate.
C – Nasal cavity.
32. Visceral Arches : 6 nos: 5 th rudimentary.
Ist arch : Mandibular arch.
IInd arch : Hyoid arch.
- Ist and IInd arches undergo further development
and meet in the ventral midline by the processes.
- Mesoderm of the Ist and IInd arch give rise to the
Vth & VIIth nerves & musculature.
- Nerve fibers of the V,VII,IX & X cranial nerves
extend into the mesoderm of the first four
visceral arches.
- Crest cells of the visceral arches give rise to
skeletal components such as Meckel's cartilage,
middle ear cartilages & mandibular bones etc.
33. 381Contribution of Facial
Processes to the Adult Face
A – Maxillary Process.
B – Mandibular
Process.
C – Median Nasal
Process
D – Lateral Nasal
Process
34. Development of Jaws - Mandible
Develops from the cartilage of the Ist
Visceral arch – Meckel’s cartilage.
Forms in membrane.
Provides a frame work around which the
bone of the mandible develops.
Centre of Ossification located – near the
future mental foramen region- starts by 7th
week I.U.
Ossification of Symphysis completed only at
second year of life.
35. 388
A – Meckel’s cartilage
B – Bone of the
Mandible
C – Tongue
D – Symphysis of
mandible
36. 389 T.S thro Mandible – 8th week I.U
A – Meckel’s cartilage.
B – Dental Lamia.
C – Tongue.
D – Neurovascular
bundle.
37. 390
A – Alveolar process –
with Bud stage of
tooth germ.
B – Neurovascular
bundle.
C – Meckel’s cartilage.
D – Tongue.
38. Meckel’s Cartilage
Doesn’t contribute to development of mandible.
Provides only a framework for development of
mandibular bone on its lateral aspect.
Resorbs after development of Mandible.
Nodular remnants may persist in symphysis till
birth.
Most distal parts of it ossify – to form Ear Ossicles
– Malleus & Incus.
Behind the body of the Mandible – the
Perichondrium persists as the Sphenomandibular
& Sphenomalleolar Ligaments.
39. 391
A – Alveolar process –
containing the
developing Tooth
germ.
B – Neurovascular
bundle.
C – Tongue.
40. 392 T.S - thro Mandible-Bell stage of Tooth germ
A - Bell stage of
Tooth germ.
B – Alveolar bone –
with Osteoclasts
in Howschip’s
lacunae & seams
of Osteoblasts.
41. Development of Cartilages - 10th to 14th week I.U
Three secondary cartilages develop within the
growing Mandible.
Largest is the Condylar Cartilage:
– Fibrous articular layer beneath the future
Condyle.
– Serves as important growth centre for
Mandible – functioning upto 20 yrs. of age.
Less important & transitory & secondary
cartilages – seen with Coronoid proces & in
Symphysis region.
42. 393 Developing Jaws – 14th week I.U
A – Body of Mandible.
B – Ramus of Mandible.
C – Sec. Condylar
Cartilage.
D – Sec. Coronoid
Cartilage.
E – Frontal Bone.
F – Parietal bone.
G – Occipital bone.
H – Squamous part of
Temporal bone.
I - Maxilla
43. Development of TMJ – 12th week I.U
Develops from mesenchyme between the
Temporal bone above & Condyle below.
Initially 2 clefts appear in the mesenchyme –
the Upper & Lower Joint cavities.
Remaining intervening mesenchyme gives
rise to Intra-articular disc.
Joint capsule develops from condensation of
surrounding mesenchyme.
At birth – the Articular fossa is flat & no
Articular Eminence – which develops later
with eruption of Deciduous dentition.
44. 394
A – Condylar cartilage.
B – Meckel’s cartilage.
C – Developing bone of
Glenoid fossa.
D – Part of developing
Articular Disc.
45. Postnatal Development & Growth of Mandible
Occurs by Remodelling of bone.
Increase in height - by formation of Alveolar bone
mainly & some by deposition on the Lower
border.
Increase in Length – by deposition on Posterior
surface of Ramus – with compensatory
resorption on Anterior surface & also by
deposition on posterior surface of Coronoid
process & resorption on Ant. Surface of Condyle.
Increase in width – by deposition on outer
surface & resorption on inner surface of
Mandible.
46. Eventhough Mandible is a single bone
Is Comprised of a number of Skeletal
Units associated with Soft tissue
Functional Matrices:
–Coronoid process acted upon by
Temporalis.
–Alveolar process influenced by Teeth.
–Condyle influenced by Lateral
Pterygoid.
47. 395A
A – At Birth.
B – At Six years.
C – In adult.
At birth No chin.
Ossification of symphysis
completed only during 2 yr.
48. 395B
A – At birth.
B – At six years.
C – In Adult.
49. Development & Growth of Maxilla
Ossifies in membrane.
Centre of Ossification – close to the site of
Decidous Canine.
Spreads into its growing processes:
– Palatine
– Zygomatic
– Frontal
– Alveolar process
50. 387
A – Body of the
Maxilla.
B – Bone extending
into Palate.
C – Nasal cavity.
51. 393
A – Body of Mandible.
B – Ramus of Mandible.
C – Sec. Condylar
Cartilage.
D – Sec. Coronoid
Cartilage.
E – Frontal Bone.
F – Parietal bone.
G – Occipital bone.
H – Squamous part
of Temporal bone.
I - Maxilla
52. 396
Decalcified T.S in the
developing Deciduous
Canine region – shows
the developing Maxilla
53. Growth of Maxilla
Occurs by surface deposition & Sutural growth –
associated with resorption.
Forces permitting growth at sutures:
– Growing:
Eye balls
Cartilagenous Nasal septum
Orbital pad of fat
Forward growth - Growing septum – Septo-
premaxillary Ligament.
Growth in Height – Development of Alveolar
Process.
54. Development of Maxillary Sinus
Begins at the 4th month of I.U
As an outpocketing of the Middle meatus
of the nose.
Small at birth – but enlarges with growth of
Maxilla.
Fully developed following eruption of
permanent teeth.
55. 397 Tracings of Lateral Skull Radiographs
R – Registration point
56. - Develops from floor of ventral pharynx.
– Starts at 4th week I.U.
- Anterior 2/3 of tongue develops from 3 swellings:
* 2 Lateral Lingual swellings
* Tuberculum Impar
- Posterior 1/3 from Copula – from III arch and
partly from IV arch.
- The Copula overgrows the II arch and
Tuberculum Impar & fuses with 2 Lateral Lingual
swellings in the midline.
Development of Tongue
57. 398
A – Lateral Lingual
swellings.
B – Tuberculum
Impar.
C – Copula.
58. 98 Sensory Innervation of Tongue
Ant. 2/3 – by:
Lingual – I arch – Sensation
Chorda Tympani
– II arch - thro Facial
– ( Pre-trematic) Taste
Post. 1/3 by: Glossopharyngeal
– IIIrd arch
A small post. Part near
Epiglottis by: Vagus via
Superior laryngeal – IV arch
Muscles - Hypoglossal
59. Thyroid gland :
- Develops by invagination of the
endoderm at the junction of the
ectodermal and endodermal parts
of Tongue.
- This invagination forms the
Thyroglossal duct.
- The site of invagination is marked
by a sideral pit called Foramen
Caecum.
60. Salivary Glands : Derived from the Oral
ectoderm.
Pituitary Gland :
- Rathke’s Pouch: Develops by the inductive
interaction of the ventral
forebrain and oral ectoderm.
61. Clinical considerations :
Facial Clefts :
Cleft lip & Cleft palate:
- Clefts of primary palate usually occur due
to the underdevelopment of the median
nasal process & the lateral nasal process
or Failure of fusion of the processes.
- Cleft of secondary palate results from the
failure of fusion of the horizontal palatal
shelves to meet.
62. Hemifacial microsomia :
- Underdevelopment of one half
of the face including TMJ,
middle ear & external ear etc.
Labial Pits :
- Small pits on lip on either side
of midline of lower lip – due to
failure of the embryonic pits to
close.
63. Lingual Anomalies :
- Bifid tongue.
- Lingual thyroid.
Developmental cysts :
- Epithelial cells entrapped along
the lines of fusion of the various
processes may give rise to cysts.
