Mandible

basic morphology and internal structure of mandible

1. PRESENTED BY:-
Dr.ChandandeepSingh

2. CONTENTS
•INTRODUCTION
•OSTEOLOGY
•ATTACHMENTS AND RELATIONS OF THE MANDIBLE
•BLOOD SUPPLY ,NERVE SUPPLY AND LYMPHATIC
DRAINAGE
•AGE CHANGES
•APPLIED ANATOMY
•REFERENCES

3. INTRODUCTION
DEFINITION:-
•The mandible(from Latin mandibula,
"jawbone") or inferior maxillary boneis the
largest, strongest and lowest bone in the face.
•It forms the lower jaw and holds the lower
teeth in place.
•It comprises of BODY,RAMUS,
ANGLE,CONDYLAR PROCESS AND CORONOID
PROCESS.

4. Parts of Mandible

5. OSTEOLOGY
•Mandible is the second boneafter clavicle to
ossify in the body.
•Parts that ossify in cartilage includes: incisive part
below the incisor teeth, coronal and condyloid
processes
•Upper half of ramusabove the level of the
mandibularforamen
•Each half of mandible ossifies from one centre
which appears in the 6
th
week of intrauterine life
in mesenchymalshealthof Meckle’scartilage.

6. •Meckel’scartilage has a close, relationship to the
mandibularnerve.
•A single ossification centre for each half of the
mandible arises in the 6
th
week of I.U. life in the
region of bifurcation of inferior alveolar nerve
into mental and incisive branches.Asthe
ossification continues, the meckel’scartilage
become surrounded and invaded by bone.
•Ossification stops at the site that will later become
the mandibularlingulafrom where the meckel’s
cartilage continues into the middle ear and
develops into the auditory ossiclesi.e. malleus
and incus.

8. THE ENDOCHONDRAL
OSSIFICATION
Endochondralossification is seen in 3 areas of
mandible:
1.The condylarprocess:-Ossification starts by14th
week.
2.The coronoidprocess:-Ossification starts by about
the 10-14 week of IU life.
3.The mental region:-Ossification starts by the 7
th
month of I.U. life.
The two halves of the mandibularbody are united
by fibrous joint at the symphysismentiwhich is
replaced by the bone within 2
nd
year.

11. THE BODY
•Consists of horseshoe-shaped
•Has two surfaces and two borders
•Surfaces:
External or Outer or Lateral
Internal or Inner or Medial
•Separated by two borders: Upperand Lower

12. FEATURES SEEN ON OUTER SURFACE
OF THE BODY
•SymphysisMenti
•MentalProtuberance
•MentalTubercles
•Mentalforamen
•Obliqueline
•Incisivefossa

14. FEATURES ON THE INNER SURFACE OF
THE BODY
•Genial tubercles
•Mylohyoidline
•Below the mylohyoidline, surface is slightly
hollowed out to form SUBMANDIBULAR FOSSA ,
which lodges submandibulargland.
•Above the mylohyoidline, there is SUBLINGUAL
FOSSA , which lodges sublingual gland.

16. UPPER BORDER or ALVEOLAR PART
•Contains 16 alveoli for the roots of teeth,
varying in size and depth, some being
multiple.
LOWER BORDER OR BASE
Near the midline, the base shows an oval
depression called as DIGASTRIC FOSSA.

17. •Quadrilateral in shape
•Consists of two surfaces ,four borders & two processes
Two surfaces include:-
Lateral
Medial
•Four border include :
Upper
Lower
Anterior
posterior
•Two processes include :-
Coronoid
Condyloid
THE RAMUS

18. BORDERS
•UPPER BORDER: Thin and curved downwards
forming the mandibularnotch.
•LOWER BORDER: Backward continuation of
base of mandible.
•ANTERIOR BORDER is thin while the
POSTERIOR BORDER is thick.

19. PROCESSES
•CORONOID PROCESS:
Flattened triangular upward projection from
the anterosuperiorpart of the ramus.
•CONDYLOID PROCESS:
Strong upward projection from posterosuperior
part of the ramus.

20. ON THE LATERAL SURFACE:
1. From The Oblique line :
buccinatorand In front of this origin: depressor labii
inferiorisand depressor anguliorisbelow the mental
foramen
2. Incisive fossa:
gives origin to MENTALIS and mental slips of
ORBICULARIS ORIS.
3. Whole of lateral surface of ramusexcept
posterosuperiorpart provides insertion to MASSETER.
4.Posterosuperior part: covered by PAROTID GLAND.
ATTACHMENTS AND RELATIONS OF
THE MANDIBLE

21. 5. Lateral surface of the neck provides insertion to the
LATERAL LIGAMENT OF TMJ.
6. Parts of both the inner and outer surfaces just
below the alveolar margins are covered by mucous
membrane of the mouth.
7. PLATYSMA is inserted into the lower border.
8. The deep cervical fascia ( investing layer) is attached
to the whole length of the lower border.

23. 1.Digastricfossa: arises ANTERIOR BELLY OF DIGASTRIC
2.Genial tubercles: arises GENIOGLOSSUS and GENIOHYOID.
3.Mylohyoidline : arises MYLOHYOID MUSCLE.
4.From an area above the posterior end of mylohyoidline:
arises SUPERIOR CONSTRICTOR OF PHARYNX.
5.PTERYGOMANDIBULAR RAPHE: Attached immediately
behind the third molar tooth in continuation with the
origin of superior constrictor .
ON THE MEDIAL SURFACE

24. 7.Below and behind the mylohyoidgroove: insertion
of MEDIAL PTERYGOID muscle .
8.At the apex of coronoidprocess: TEMPORALIS is
inserted ;extend downwards on ant. Border of
ramus.
9.Into the pterygoidfovea: insertion of LATERAL
PTERYGOID.
10.Sphenomandibular ligament: is attached to the
lingula.

26. FORAMINA AND RELATIONS TO
NERVES AND VESSELS
1.MENTAL FORAMEN: Transmits the mental nerve
and vessels.
2.MANDIBULAR FORAMEN: Inferior alveolar nerve
and vessels enter the mandibularcanal via this
foramen.
3.Mylohyoidnerve and vessels lie in the mylohyoid
groove.

27. 4.The lingual nerve is related to the medial
surface of the ramusin front of the mylohyoid
groove.
5.The area above and behind the mandibular
foramen is related to the INFERIOR ALVEOLAR
NERVE and VESSELS ; and MAXILLARY ARTERY
respectively.
6.The massetericnerve and vessels pass
through the mandibularnotch.
7.The auricotemporalnerve is related to the
medial side of the neck of the mandible.

28. BLOOD SUPPLY OF THE MANDIBLE
1.Central blood supply via THE INFERIOR
ALVEOLAR ARTERY except the coronoidprocess ,
which is supplied by temporalismuscle vessels.
2.Peripheral blood supply via the PERIOSTEUM..
periostealsupply ,which generally runs parallel
to cortical surfaces of bone, giving off nutrient
vessels those penetrate cortical bone and
anastomosewith the branches of inferior
alveolar artery.

29. NERVE SUPPLY OF MANDIBLE
•It is basically derived from mandibularbranch of trigeminal
nerve.
1. The long buccalnerve: The anterior division of the
mandibularnerve. It supplies mucosa opposite the last
three mandibularmolars on their buccalaspect.
2. The inferior alveolar nerve: The posterior division of the
mandibularnerve. It supplies all lower jaw teeth, lower lip,
buccalmucosa from the incisors to the premolar & the skin
over the chin.
3. The lingual nerve: The posterior division of the mandibular
nerve. It gives sensory supply to the anterior 2/3
rd
of
tongue, the mucosa on the lingual aspect of the lower
teeth & the floor of mouth.

30. LYMPHATIC DRAINAGE
•Most of the mandible & lower teeth drain into the
submandibulargroup of lymph nodes .
•Except a small wedge in the symphysisregion & the
lower incisors which drain into the submentalgroup of
lymph nodes.
•From the submentalgroup the lymph drains to the
submandibulargroup of nodes.
•Most of the submandibularnodes ultimately drain to the
jugulo-omohyoidgroup of deep cervical lymph nodes.
•Few extremely posterior submandibularnodes drain to
jugulo-digastricgroup of deep cervical lymph nodes.

31. AT BIRTH
The body of the bone is a mere shell, containing the
sockets of the two incisor, the canine, and the two
deciduous molar teeth, imperfectly partitioned off
from one another.
The mandibularcanalis of large size, and runs near
thelower border of the bone; the mental foramen
opens beneath the socket of the first deciduous
molar tooth.
The angle is obtuse (175°), and the condyloidportion
is nearly in line with the body. The coronoidprocess
is of comparatively large size, and projects above the
level of the condyle
AGE CHANGES IN THE MANDIBLE

33. CHILDHOOD
•The two segments of the bone become joined at the
symphysis, from below upward, in the first year; but
a trace of separation may be visible in the beginning
of the second year, near the alveolar margin.
•The body becomes elongated in its whole length,
but more especially behind the mental foramen, to
provide space for the three additional teeth
developed in this part.
•The depth of the body increases owing to increased
growth of the alveolar part, to afford room for the
roots of the teeth.
•The angle becomes less obtuse, owing to the
separation of the jaws by the teeth; about the fourth
year it is 140°.

35. 1.After the eruption of permanent teeth the
mental foramen lies mid-way between the upper &
lower borders of the bone.
2. Growth of the ramitakes place posteriorly&
vertically by the process of remodeling. Posterior
growth accommodates the eruption of permanent
molars & reduces the angle of mandible to almost
110º-115º. Vertical growth allows the condylar
process to lie higher than the coronoidprocess.
IN ADULTS

37. 1. Teeth fall out and the alveolar border is
absorbed so that the height of the body is
markedly reduced.
2. The mental foramen and the mandibularcanal
are close to the alveolar border.
3. The angle again becomes obtuse about 140
degrees because the ramusis oblique.
IN OLD AGE

39. APPLIED ANATOMY OF MANDIBLE
1.Parasymphysisregionlateral to the mental
prominence is a naturally weak area susceptible for
parasymphysealfracture. This is because of the
presence of incisive fossaand mental foramen.
2.The body of the mandible is considerably thicker than
the ramusand the junction between these two
portions constitutes a line of structural weakness.
3.Strength of the lower jaw varies with the presence or
absence of teeth. The presence of impacted lower
third molars or excessive long roots of canines make
the area more vulnerable for fracture.

40. 4. With the advancing age, the loss of teeth and resorption
of alveolar bone leads to a decrease in the vertical height
of the mandible, making it prone to fracture.
5. The slender neck of the mandibularcondylesrenders it
particularly liable to fracture as a result of direct violence
applied to the chin.
This acts as a safety mechanism , as a fracture of neck of
the condyleprevents injury to the middle cranial fossa.
Direct blow to the chin region can lead towards fracture
of one or both condyles.
Sideways blow can bring about fracture of the opposite
condylarneck along with the parasymphysisfracture at
the same side of the blow.

41. 6. It is possible to split the ramusof the mandible
in sagittalplane bilaterally thereby correcting
micrognathiathis procedure is called sagittalsplit
osteotomy.
7. Osteomyelitisof the mandible is more
commoner than the maxilla as the maxilla has
rich blood supply.

42. REFERENCES
•B.D CHAURASIA’S HUMAN ANATOMY –6
TH
EDITION
•TEXTBOOK OF ANATOMY BY INDERBIR SINGH-5
TH
EDITION
•GRAY’S ANATOMY –2
ND
EDITION
•SICHER AND DuBRUL’SORAL ANATOMY –8
TH
EDITION
•TEXTBOOK OF ORAL AND MAXILLOFACIAL
SURGERY , NEELIMA ANIL MALIK-2
ND
EDITION
•INTERNET