Dr. Ratna Deepika, Oral and Maxillofacial Surgery

1. EMBRYOLOGY OF
THE HEAD & NECK -
PART II
-Dr.RATNA DEEPIKA SESHAGIRI
MDS PART I

2. CONTENTS:
• Development of Mandible
• Development of Temporomandibular joint
• Development of Palate
• Development of Tongue
• Development of Tonsils
• Development of Salivary Glands
• Development of muscle
• Conclusion
• References

3. DEVELOPMENT OF MANDIBLE:
• The cartilages and bones of the mandibular skeleton
form from embryonic neural crest cells that
originated in the mid and hindbrain of the neural
folds.
• The first structure to develop in the region of the
lower jaw is the mandibular division of the
trigeminal nerve that precedes the ectomesenchymal
condensation forming the first branchial arch.
• The mandible is derived from ossification of an
osteogenic membrane formed from
ectomesenchymal condensation at 36-38 days of
development.

4. • A single ossification centre for each half of the
mandible arises in the sixth week intra uterine
life in the region of bifurcation of alveolar
nerve and artery in to mental and incisive
branches.
• Ossification membrane is lateral to Meckel’s
cartilage and its accompanying neurovascular
bundle.
• Ossification spreads from the primary centre
below and around the inferior alveolar nerve
and its incisive branches , and upwards to
form a trough for the developing teeth.

5. • Spread of intramembranous ossification
dorsally and ventrally forms the body and
ramus of mandible.
• Ossifications stops dorsally at the site that will
become mandibular lingula, from where
Meckel’s cartilage continue in to the middle
ear.
• Meckel’s cartilage diverges dorsally to end in
the tympanic cavity of each middle ear, which
is derived from the first pharyngeal pouch,
and is surrounded by the forming petrous part
of temporal bone.

6. • The dorsal end of the Meckel’s cartilage ossifies to
form basis of two of the auditory ossicles
Malleus and Incus
• The third ossicle which is derived primarily from
the cartilage of second branchial arch(Reichert’s
cartilage)
Stapes

8. • Parts of Meckel’s cartilage transform in to
Sphenomandibular
ligament
Malleolar
ligament

9. • Meckel’s cartilage
dorsal to the mental
foramen undergoes
resorption on its
lateral surface at the
same time as
intramembranous
bony trabeculae are
forming immediately
lateral to the resorbing
cartilage.

10. Initial woven bone
Lamellar bone+
Haversian systems
5th month
intrauterine

11. • Secondary accessory cartilages appear between the
10th and 14th week i.u to form
Head of condyle
Part of coronoid process
Mental protuberance
• The appearance of this secondary cartilages is
dissociated from the primary branchial and
chondrocranial cartilages.
• The secondary cartilage of coronoid process develops
within the temporalis muscle as its predecessor.

12. • The coronoid accessory cartilage becomes
incorporated in to the expanding
intramembranous bone of the ramus and
disappears before birth.
• In the mental region ,on either side of the
symphysis, one or two small cartilages
appear and ossify in the 7th month i.u to
form variable number of mental ossicles
in fibrous tissue of symphysis.

13. • The condylar secondary cartilage appears during the 10th week i.u as a
cone shaped structure in the ramal region.
• Cartilage of condylar head increase by
Interstitial growth Appositional growth

14. • Condylar cartilage serves as a important centre of growth
for ramus and body of the mandible.
• By14th week, first evidence of endochondral bone appear in
condylar region.
• Change in mandibular position and form are related to
direction and amount of condylar growth.
• The continuing presence of the cartilage provides a
potential for continued growth ,which is realized in
conditions of abnormal growth such as Acromegaly.

15. At birth At childhood
At Adult At Senility

16. Syndromes associated with mandible:
• Down’s syndrome
• Marfan’s syndrome
• Turners syndrome
• Klinefelter’s syndrome
• Pierre-robin syndrome
• Treacher collins syndrome

17. Other Congenital anomalies:
• Agnathia
• Micrognathia
• Macrognathia
• Facial Hemihypertrophy
• Facial Atrophy

18. Development of Temporomandibular joint:
• The Temporomandibular joint is a
secondary development ,both in its
evolution and embryological history.
• The joint between malleus and incus
that develops at the dorsal end of the
Meckel’s cartilage is phylogenetically
the primary jaw joint.
• When the temporomandibular joint
forms at 10 week i.u., both the malleo-
incudal and definitive jaw joints move
in synchrony for about 8 weeks in fetal
life .

19. • TMJ develops from 2 blastemas :
Condylar blastema Temporal blastema
• Between 10-12 weeks of I.U life
Condylar blastema
develops from the
secondary condylar
cartilage
Temporal blastema
arises from the otic
capsule

20. • During the 10th week intrauterine two clefts
develop in the interposed vascular fibrous
connective tissue, forming the two joint cavities
and thereby defining the intervening articular disk.
• Inferior compartment- 10th week
Separating the future disk from the developing
condyle
• Upper compartment – 11 ½ week.
After which cavitation occurs, due to muscle
movement, by rupture of small spaces to coalesce into
functional cavities.
1. Fibrous layer
2. Cartilage
3. Bone
4. Bone marrow

21. • Condensation of mesenchyme
forms the basis of joint
capsule, which progressively
isolates the joint from the
surrounding tissues.
• The joint capsule composed of
fibrous tissue, recognizable by
the 11th week i.u., forms lateral
ligaments

22. • The Temporomandibular joint of the new born
child is comparatively lax structure, with
stability solely dependant upon the capsule.
• At birth – Mandibular fossa is almost flat and
bears no articular tubercle.
• At 7 years –After the eruption of permanent
teeth, Articular tubercle begin to become
prominent.
• After 12 years- the disk becomes S-shaped,
more compact, more collagenous and less
cellular.
• Mature disk- Avascular and Aneural in its
central portion,but is filled with vessels,
nerves and elastic fibres posteriorly.

23. Development of Palate:

24. Early palate formation:
• The primitive stomodeum that forms a wide
central shallow depression in the face is limited in
its depth by the oropharyngeal membrane .
• The characteristically deep oral cavity is formed
by ventral growth of prominences surrounding
the stomodeum .
• The stomodeum establishes as an
oronasalpharyngeal chamber and entrance to the
gut on the 28th day, when the dividing
oropharyngeal membrane disintegrates, providing
continuity of passage between the mouth and
pharynx.

25. • The stomodeal chamber divides into separate
oral and nasal cavities when the frontonasal
and maxillary prominences develop
horizontal extensions into the chamber.
• Frontonasal prominence
Single median primary
palate
• Maxillary prominences
Two lateral palatal shelves

26. • The shelves elevate unevenly with the anterior
third “flipping up” followed by an oozing
“flow” of the posterior two-thirds.
• Elevation of shelves enables their mutual
contact in the midline, the primary palate
anteriorly and the nasal septum superiorly.
• The shelves also fuse with the nasal septum ,
except posteriorly, where the soft palate and
uvula remain unattached.
• Ossification provides the basis for the anterior
bony hard palate. The posterior third of palate
remains unossified.

27. SECONDARY PALATE FORMATION:
• The three elements that make up the
secondary palate formation
Two lateral maxillary
palatal shelves
Primary palate
• Palatine shelves ascend to attain a
position above the tongue and fuse;
forming Secondary palate.
• Incisive foramen is the midline
landmark between primary & secondary
palate.

28. Developmental anomalies of palate:
• Cleft palate:
 Unilateral cleft palate and
lip
 Bilateral cleft palate and lip
 Bifid uvula
• Epstein pearls
• Bohn’s nodules
• Nasopalatine duct cyst

29. Syndromes associated with cleft palate:
• Achondroplasia
• Cleiodocranial dysplasia
• Treacher Collins syndrome
• Fetal alcohol syndrome
• Goltz-Gorlin syndrome(Focal dermal hypoplasia syndrome)
• Marfan syndrome
• Pierre Robin syndrome
• Van-der Woude syndrome

30. • Stickler syndrome(Pierre Robin sequence)
• Oro-facial Digital syndrome
• Apert syndrome
• Goldenher syndrome
• Ehler danlos syndrome
• Lowry -Miller syndrome
• Velo Cardiofacial syndrome(DiGeorge syndrome)

31. Syndromes associated with cleft lip:
• Achondroplasia
• Fetal alcohol syndrome
• Goldenher syndrome
• Goltz-Gorlin syndrome (Focal dermal hypoplasia syndrome)
• Van- der Woude syndrome
• Median facial dysplasia syndrome

32. DEVELOPMENT OF TONGUE:
• The tongue arises in the
ventral wall of the
primitive oropharynx
from the inner lining of
the four branchial
arches.

33. • During the 4th week i.u., paired lateral
thickenings of mesenchyme appear
on the internal aspect of the first
branchial arch to form the lingual
swellings.
• Between the swellings a median
eminence appears ,the tuberculum
impar (unpaired tubercle) whose
caudal border is marked by a blind
pit.
• This pit, the Foramen caecum, marks
the site of origin of the thyroid
diverticulum, an endodermal duct that
appears during the somite period.

34. • The diverticulum migrates caudally
ventral to the pharynx ,as the
thyroglossal duct, which bifurcates
and subdivides to form the thyroid
gland.
• The lingual swellings grow and fuse
with each other, emcompassing the
tuberculum impar,to provide
ectodermal derived body of the
mucosa of the tongue.

35. • The ventral bases of the
second, third and fourth
branchial arches elevate in to a
united, single midventral
prominence known as the
Copula.
• A posterior subdivision of this
prominence is identified as the
hypobranchial eminence.
• A V-shaped sulcus terminalis
,whose apex is the foramen
caecum, demarcates the mobile
body of the tongue from its
fixed root.

36. • The line of the sulcus
terminalis is marked by 8-12
large circumvallate papillae
that develop at 2-5 months
i.u.
• Fungiform papillae develop
on the dorsal surface of the
tongue-11 weeks i.u.
• Development of Filiform
papillae is not complete till
postnatally.
• Gustatory cells – 7 th week
i.u.

37. Developmental anomalies of tongue:
• Ankyloglossia(Tongue tie)
• Bifid tongue
• Microglossia
• Macroglossia
• Aglossia

38. Syndromes associated with tongue:
• Oro-facial digital syndrome- Cleft
tongue
• Down’s syndrome
• Stickler syndrome
• Hurler syndrome
• Beckwith-wiedemann syndrome
• Hanhart Syndrome

39. Development of tonsils:

40. Development of tonsils:
• The endoderm lining the second pharyngeal
pouch between the tongue and soft palate
invades the surrounding mesenchyme as a
solid group of buds.
• Central parts of these buds degenerate to
form TONSILLAR CRYPTS .
Invading lymphoid cells surround the crypts
To group as lymphoid follicles

41. • Lymphoid tissue invades into
 Palatine region
 Posterior region
 Pharyngeal region
 Lingual region
 Auditory region
• These lymphoid masses encircle the
oropharynx to form Waldayers ring .
• It is a ring of immunodefensive
tissues that grows postnatally in the
oropharynx .

42. • Palatine tonsils arise at site of
second pharyngeal arch.
• Pharyngeal and Lingual tonsils
develop in mucosa of posterior
wall of the pharynx and roof of the
tongue.
• Tubal tonsils are formed by the
lateral extensions of the lymphoid
tissue posterior to the openings of
the auditory tubes.

43. Development of salivary glands:
• During fetal life, each salivary
gland is formed at a specific
location in the oral cavity
through the growth of the bud of
the oral epithelium into the
underlying mesenchyme.
• The three major sets of salivary
glands-
 Parotid gland
 Submandibular gland
 Sublingual gland

44. Developmental stages:
• Stage 1: Induction of oral epithelium by
underlying mesenchyme.
• Stage 2: Formation and growth of
epithelial cord.
• Stage 3: Initiation of branching in
terminal parts of epithelial cord and
continuation of glandular differentiation.
• Stage 4: Repetitive branching of
epithelial cord and lobule formation.
• Stage5: Canalization of presumptive
ducts.
• Stage 6: Cytodifferentiation.

45. Cells of salivary glands:
• The lining epithelium of the ducts,
tubules and acini differentiate both
morphologically and functionally.
• Inner epithelial layer - secretory cells
(serous and mucous)
• Outer epithelial layer- myoepithelial
cells (derived from neural crest)

47. Major Salivary Glands:
• Parotid Gland:
 Purely serous.
 First to appear, 6th week i.u.
 Appears on the inner cheek near the
angle of the mouth and then grows
back to the ear.
 Stenson’s duct opens in buccal
mucosa opposite maxillary 2nd
molar.

48. • Submandibular Gland:
 Mixed serous and mucus.
 Appear late in the 6th week prenatally.
 Appears bilaterally in the floor of the
mouth.
 Wharton’s duct opens in the floor of the
mouth on either side of the lingual frenum.
• Sublingual Gland:
 Predominantly mucus.
 Appears around 8th week i.u.
 Appears lateral to the submandibular gland.
 Bartholin’s duct opens into the Wharton’s
duct and drains through the sublingual
caruncle.

49. Development of Muscle:
• Craniofacial voluntary muscles develop from paraxial mesoderm that
condenses rostrally as incompletely segmented somitomeres and
segmented somitomeres of occipital and rostral cervical regions.
• Myomeres of somitomeres +Myotomes of the somites
Myoblasts
divide and fuse
Myotubes
Cease further mitosis
Myocytes

51. • The mesenchymal component of the pharyngeal arches gives rise to special
visceral (striated) musculature, which is voluntary in nature.
MESENCHYME MUSCLES
1st arch Muscles of Mastication
2nd arch Muscles of Facial
Expression
3rd arch Stylopharyngeus
4th arch Pharyngeal muscles,
Palatopharyngeus, Levator
veli palatini, Uvular
muscles
6th arch Laryngeal muscles
Occipital Somites Muscles of the tongue

52. Schematic description
of the embryonic
origins of (clockwise
from upper right) the
ocular,masticatory,
facial, pharyngeal,
neck, and tongue
muscles.

53. Timeline for muscle development
Orofacial musculature:
1. First to develop in the body.
2. Genioglossus and Geniohyoid- at 32 to 36 days i.u.
3. Mylohyoid & Anterior Belly of Digastric-first to develop from the 1st
arch.
Palatal musculature:
1. Tensor Veli Palatini- 40 days post conception.
2. Levator Veli Palatini, Palatopharyngeus- around 45 days.
3. Uvular muscles-when palatal shelves fuse.
4. Palatoglossus is the last to develop.

54. Masticatory musculature:
1. Develop as individual entities from the 1st
arch mesenchyme.
2. The muscles need constant reattachment
due to remodelling of the mandible during
growth phase.

55. MUSCLES OF FACIAL EXPRESSIONS

56. MUSCLES OF MASTICATION

57. Conclusion:
• Embryology helps us to understand the normal
growth pattern of a variety of structures and the
time at which they complete their growth.
• So embryology is important for providing correct
treatment modalities at an appropriate time.

58. References:
• CRANIOFACIAL EMBRYOLOGY : GEOFFERY SPERBER
• TEN CATE’S ORAL HISTOLOGY
• LANGMAN’S MEDICAL EMBRYOLOGY
• TEXTBOOK OF HUMAN EMBRYOLOGY INDERBIR SINGH