Embryolgy of mandible

1. EVOLUTION &
EVOLUTION &
DEVELOPMENT OF
DEVELOPMENT OF
MANDIBLE
MANDIBLE
-
- Dr. Patil Shrish.
Dr. Patil Shrish.
PG in Dept of Anatomy
PG in Dept of Anatomy

2. Mandible
Mandible
-The strongest and largest skull bone in
-The strongest and largest skull bone in
man.
man.
-Only bone in human skull to move
-Only bone in human skull to move
independently, with the exception of
independently, with the exception of
ear ossicles.
ear ossicles.

3.  Various modifications from the jaw of
Various modifications from the jaw of
cartilaginous fishes to present day.
cartilaginous fishes to present day.

4. Family tree
Family tree
of
of
vertebrates
vertebrates

5. Simplifie
Simplifie
d family
d family
tree of
tree of
primates
primates

6. Jaws of ray-finned fish and a
Jaws of ray-finned fish and a
primitive crosspoterygian
primitive crosspoterygian

7. Jaws of Labyrinthodont, primitive
Jaws of Labyrinthodont, primitive
reptile & reptile
reptile & reptile

8. Jaws of mammal-like reptiles and
Jaws of mammal-like reptiles and
mammals
mammals

9. Elasmobranch
Elasmobranch

10.  At no time in it’s evolution has there
At no time in it’s evolution has there
been a cessation in function, although it
been a cessation in function, although it
no longer is used as a nut-cracker /
no longer is used as a nut-cracker /
bone –cruncher.
bone –cruncher.

11.  The successive changes which an
The successive changes which an
individual passes through, during a life
individual passes through, during a life
time are strikingly paralleled in the
time are strikingly paralleled in the
evolutionary emergence of the human
evolutionary emergence of the human
race.
race. (Walter & sayles-fig519-520)
(Walter & sayles-fig519-520)

12. •The golden age of efficiency is past &
The golden age of efficiency is past &
now it is turned to other uses.
now it is turned to other uses.
 Instead of being employed
Instead of being employed
as a means of
as a means of terrifying
terrifying
enemies
enemies by frightful
by frightful
gnashing of bared teeth, it
gnashing of bared teeth, it
has become a part of the
has become a part of the
skeletal framework for the
skeletal framework for the
display of
display of friendliness
friendliness and
and
persuasive diplomacy.
persuasive diplomacy.

13.  In some monkeys and apes, the lower
In some monkeys and apes, the lower
jaw may make up as much as 40% of
jaw may make up as much as 40% of
the total weight of skull; but in modern
the total weight of skull; but in modern
man it falls to less than 15%.
man it falls to less than 15%.
Mandible of gorilla
Mandible of gorilla

14. EVOLUTION
EVOLUTION
- A TIME
- A TIME
CHART
CHART

15.  Pithecanthropus-
Pithecanthropus- Pliocene
Pliocene
 Heidelberg man-
Heidelberg man- Lower pleistocene
Lower pleistocene
 Neanderthal man-
Neanderthal man- Lower pleistocene
Lower pleistocene
 Grimaldi race-
Grimaldi race- Betn lower & mid pleistocene
Betn lower & mid pleistocene
 Cro-magnon race-
Cro-magnon race- Mid. pleistocene
Mid. pleistocene
 Chancelade race-
Chancelade race- Upper pleistocene
Upper pleistocene
 Homo sapiens-
Homo sapiens- Holocene
Holocene

16. Pithecanthropus (Java man)
Pithecanthropus (Java man)
Large, heavily built,
Large, heavily built,
receding
receding
symphysis- no
symphysis- no
chin, large digastric
chin, large digastric
fossa situated entirely
fossa situated entirely
on the lower margin of the
on the lower margin of the
bone. This is incompatible with
bone. This is incompatible with
functioning of the tongue for
functioning of the tongue for
articulate speech.(Dubois).
articulate speech.(Dubois).

17. Heidelberg man(Mauer jaw)
Heidelberg man(Mauer jaw)
 Thick and massive,
Thick and massive,
generally ape like.
generally ape like.
 A powerful ramus with
A powerful ramus with
great breadth.
great breadth.
 Receding anterior
Receding anterior
symphysis.
symphysis.
 No simian plate.
No simian plate.
 Dental arcade is also
Dental arcade is also
more human rather
more human rather
than the U curve of
than the U curve of
modern anthropoids.
modern anthropoids.

18. Neanderthal man
Neanderthal man
 Chin is exactly
Chin is exactly
interposed between
interposed between
jaws of anthropoid
jaws of anthropoid
apes and those of
apes and those of
modern men.
modern men.
 Strong build with large
Strong build with large
molar alveoli.
molar alveoli.
 Viewed from above-
Viewed from above-
exactly reversed to
exactly reversed to
that of modern man.
that of modern man.
 Region of angle is thin
Region of angle is thin
& deviates greatly
& deviates greatly
from the vertical.
from the vertical.

19. Neanderthal man
Neanderthal man

20. Neanderthal man
Neanderthal man
 Proportions of condyles are simian.
Proportions of condyles are simian.
 Coronoid apophysis is low, broad and
Coronoid apophysis is low, broad and
blunt.
blunt.
 These are indications of the strength of
These are indications of the strength of
whole masticatory apparatus and of the
whole masticatory apparatus and of the
relatively greater development of
relatively greater development of
chewing muscles than of biting muscles.
chewing muscles than of biting muscles.

21. Grimaldi race (Negroid race)
Grimaldi race (Negroid race)
 Jaw is strong, body is very thick, ramus
Jaw is strong, body is very thick, ramus
is broad and low.
is broad and low.
 Chin not greatly developed.
Chin not greatly developed.
 Strongly marked alveolar prognathism.
Strongly marked alveolar prognathism.
 Dental arch is less widely divergent than
Dental arch is less widely divergent than
in higher races.
in higher races.

22. Cro-magnon race
Cro-magnon race
Cro-Magnon is the name of a rock shelter near
Cro-Magnon is the name of a rock shelter near
Dordogne France
Dordogne France
The mandible is robust, with
The mandible is robust, with
massive ascending ramus (the upward
massive ascending ramus (the upward
projection of the lower jaw, where it
projection of the lower jaw, where it
attaches to the skull), has strongly
attaches to the skull), has strongly
developed points of muscular
developed points of muscular
attachment, and a quite prominent
attachment, and a quite prominent
chin.
chin.

23. Chancelade race
Chancelade race
 Jaw is narrow & strong.
Jaw is narrow & strong.
 Remarkable for the breadth of it’s ramus.
Remarkable for the breadth of it’s ramus.
 Chin forms a very broad & prominent
Chin forms a very broad & prominent
projection.
projection.
 Flaring gonial angles.
Flaring gonial angles.
 Testify to a considerable development of
Testify to a considerable development of
muscles of mastication.
muscles of mastication.
 Special character is
Special character is
presence of
presence of
‘Torus mandibularis’.
‘Torus mandibularis’.

24. Homo sapiens
Homo sapiens

26. DEVELOPMENT OF MANDIBLE
DEVELOPMENT OF MANDIBLE
 The primary mandible is represented by the
The primary mandible is represented by the
Meckel’s cartilage.
Meckel’s cartilage.
 The ossifying parts of the mandible lie, at first
The ossifying parts of the mandible lie, at first
altogether on the outer side of the cartilage,
altogether on the outer side of the cartilage,
subsequently extending below it and then up
subsequently extending below it and then up
on it’s inner side to enclose it.
on it’s inner side to enclose it.
 The widening roof of the mouth has been met
The widening roof of the mouth has been met
by maxillary growth & formation of
by maxillary growth & formation of
membranous bones outside the original
membranous bones outside the original
arcade: this has necessitated a concomitant
arcade: this has necessitated a concomitant
formation outside the original mandible.
formation outside the original mandible.

27. DEVELOPMENT OF MANDIBLE
DEVELOPMENT OF MANDIBLE
 The first branchial arch gives rise to both
The first branchial arch gives rise to both
maxillary and mandibular processes.
maxillary and mandibular processes.
 Meckel’s cartilage extends from the
Meckel’s cartilage extends from the
future malleus to the future symphysis
future malleus to the future symphysis
mentalis.
mentalis.
 The dorsal part of the Meckel’s cartilage
The dorsal part of the Meckel’s cartilage
proceeds towards the symphysis
proceeds towards the symphysis
mentalis but fusion is denied.
mentalis but fusion is denied.

28. Ossification.
Ossification.
 The mandible appears immediately
The mandible appears immediately
external to the cartilage & begins to
external to the cartilage & begins to
ossify at 6-7 weeks of IUL.
ossify at 6-7 weeks of IUL.
 The mandibular cartilage & mandible
The mandibular cartilage & mandible
are believed to arise from neural crest
are believed to arise from neural crest
cells.
cells.

29. DEVELOPMENT OF MANDIBLE
DEVELOPMENT OF MANDIBLE
 Morphogenesis of the medial region of
Morphogenesis of the medial region of
the developing mandible is regulated by
the developing mandible is regulated by
multiple signaling pathways.
multiple signaling pathways.
 Studies suggest that in the medial
Studies suggest that in the medial
region of the developing mandible, FGF-
region of the developing mandible, FGF-
mediated signaling is involved in
mediated signaling is involved in
growth-promoting interaction, whereas
growth-promoting interaction, whereas
BMP
BMP (Bone Morphogenetic Protein)
(Bone Morphogenetic Protein) -mediated
-mediated
signaling is involved in chondrogenesis.
signaling is involved in chondrogenesis.

30.  Experimental evidence indicates that the
Experimental evidence indicates that the
mandibular primordia are specified as at
mandibular primordia are specified as at
least two independent functional regions:
least two independent functional regions:
two large lateral (proximal) regions where
two large lateral (proximal) regions where
morphogenesis is dependent on FGF-8
morphogenesis is dependent on FGF-8
signaling, and a small medial region
signaling, and a small medial region
where morphogenesis is independent of
where morphogenesis is independent of
FGF-8 and dependent on other signals.
FGF-8 and dependent on other signals.

31. Factors thought to be responsible for
Factors thought to be responsible for
ossification-
ossification-
 Mandibular cartilage itself.
Mandibular cartilage itself.
 Epithelio-mesenchymal interactions
Epithelio-mesenchymal interactions
between oral epithelium & subjacent
between oral epithelium & subjacent
mesenchyme.
mesenchyme.
 Teeth are also considered to affect
Teeth are also considered to affect
mandibular development, especially the
mandibular development, especially the
body.
body.

32.  At birth the two halves of mandible are
At birth the two halves of mandible are
united at the symphysis by a
united at the symphysis by a
cartilaginous joint that allows further
cartilaginous joint that allows further
forward growth at the body of the bone
forward growth at the body of the bone
until synostosis occurs during the first 3
until synostosis occurs during the first 3
years of life.
years of life.
 A secondary cartilage in the condylar
A secondary cartilage in the condylar
process is responsible for most of the
process is responsible for most of the
later growth in length of the mandible.
later growth in length of the mandible.

33.  Mandible of the young child is characterized
Mandible of the young child is characterized
by it’s diminutive appearance.
by it’s diminutive appearance.
 Chin is poorly developed.
Chin is poorly developed.
 With increasing age
With increasing age
 It becomes more massive
It becomes more massive
 Squared in character
Squared in character
 Forward contour of lower jaw becomes flattened
Forward contour of lower jaw becomes flattened
 Mental region becomes progressively prominent.
Mental region becomes progressively prominent.

34.  The whole face becomes deeper in the
The whole face becomes deeper in the
AP plane.
AP plane.
 Concept of ‘Growth equivalents’- i.e.,
Concept of ‘Growth equivalents’- i.e.,
direct inter-relationship between cranial
direct inter-relationship between cranial
base, nasomaxillary complex and
base, nasomaxillary complex and
mandible.
mandible.

35. Jaw suspension
Jaw suspension
 Huxley (1876) proposed terme for the
Huxley (1876) proposed terme for the
manner in which the qudrate portion of
manner in which the qudrate portion of
the pterygoquadrate cartilage is related
the pterygoquadrate cartilage is related
to the otic region.
to the otic region.
 Some other authors applied the same/
Some other authors applied the same/
similar terms to indicate the manner in
similar terms to indicate the manner in
which the entire upper jaw was
which the entire upper jaw was
suspended from the skull, leading to
suspended from the skull, leading to
confusing terminologies.
confusing terminologies.

36.  Hyostyly- Hyoid braced
Hyostyly- Hyoid braced
 Autostyly- Self braced. Quadrate
Autostyly- Self braced. Quadrate
articulates directly against, and often
articulates directly against, and often
fuses with the otic region of the
fuses with the otic region of the
chondrocranium.
chondrocranium.
 Amphistyly- Both hyomandibular &
Amphistyly- Both hyomandibular &
quadrate articulate against the
quadrate articulate against the
chondrocranium.
chondrocranium.

37. Hyostyly
Hyostyly
 Seen in Sharks and Sturgeons
Seen in Sharks and Sturgeons

38. Autostyly
Autostyly
 Found in tetrapods other than
Found in tetrapods other than
mammals.
mammals.

39. Amphistylic
Amphistylic
 Found in primitive elasmobranchs
Found in primitive elasmobranchs

40. Variation of autostylic
Variation of autostylic
 Seen in lung fishes,
Seen in lung fishes,
holocephalians and Polypterus.
holocephalians and Polypterus.

41. Teleost variation of hyostylic
Teleost variation of hyostylic
 Seen in Amia and teleosts.
Seen in Amia and teleosts.

42. Skull of Sphenodon
Skull of Sphenodon
Tuatara have been referred to as living fossils. This means
that they have remained mostly unchanged throughout
their entire history, which is approximately 220 million
years.

43. Skull of Boa constrictor
Skull of Boa constrictor

44. Skull of monkey
Skull of monkey