basic morphology and internal structure of mandible

1. PRESENTED BY:-
Dr.Chandandeep Singh

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 bone is 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 bone after 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 ramus above the level of the
mandibular foramen
• Each half of mandible ossifies from one centre
which appears in the 6th week of intrauterine life
in mesenchymal shealth of Meckle’s cartilage.

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

8. THE ENDOCHONDRAL
OSSIFICATION
Endochondral ossification is seen in 3 areas of
mandible:
1. The condylar process:- Ossification starts by14th
week.
2. The coronoid process:- Ossification starts by about
the 10-14 week of IU life.
3. The mental region:- Ossification starts by the 7th
month of I.U. life.
The two halves of the mandibular body are united
by fibrous joint at the symphysis menti which is
replaced by the bone within 2nd 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: Upper and Lower

12. FEATURES SEEN ON OUTER SURFACE
OF THE BODY
• Symphysis Menti
• Mental Protuberance
• Mental Tubercles
• Mental foramen
• Oblique line
• Incisive fossa

14. FEATURES ON THE INNER SURFACE OF
THE BODY
• Genial tubercles
• Mylohyoid line
• Below the mylohyoid line, surface is slightly
hollowed out to form SUBMANDIBULAR FOSSA ,
which lodges submandibular gland.
• Above the mylohyoid line, 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 mandibular notch.
• 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 anterosuperior part of the ramus.
• CONDYLOID PROCESS:
Strong upward projection from posterosuperior
part of the ramus.

20. ON THE LATERAL SURFACE:
1. From The Oblique line :
 buccinator and In front of this origin: depressor labii
inferioris and depressor anguli oris below the mental
foramen
2. Incisive fossa:
 gives origin to MENTALIS and mental slips of
ORBICULARIS ORIS.
3. Whole of lateral surface of ramus except
posterosuperior part 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. Digastric fossa: arises ANTERIOR BELLY OF DIGASTRIC
2. Genial tubercles: arises GENIOGLOSSUS and GENIOHYOID.
3. Mylohyoid line : arises MYLOHYOID MUSCLE.
4. From an area above the posterior end of mylohyoid line:
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 mylohyoid groove: insertion
of MEDIAL PTERYGOID muscle .
8.At the apex of coronoid process : TEMPORALIS is
inserted ;extend downwards on ant. Border of
ramus.
9.Into the pterygoid fovea: 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 mandibular canal via this
foramen.
3. Mylohyoid nerve and vessels lie in the mylohyoid
groove.

27. 4. The lingual nerve is related to the medial
surface of the ramus in 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 masseteric nerve and vessels pass
through the mandibular notch.
7. The auricotemporal nerve 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 coronoid process ,
which is supplied by temporalis muscle vessels.
2. Peripheral blood supply via the PERIOSTEUM..
periosteal supply ,which generally runs parallel
to cortical surfaces of bone, giving off nutrient
vessels those penetrate cortical bone and
anastomose with the branches of inferior
alveolar artery.

29. NERVE SUPPLY OF MANDIBLE
• It is basically derived from mandibular branch of trigeminal
nerve.
1. The long buccal nerve: The anterior division of the
mandibular nerve. It supplies mucosa opposite the last
three mandibular molars on their buccal aspect.
2. The inferior alveolar nerve: The posterior division of the
mandibular nerve. It supplies all lower jaw teeth, lower lip,
buccal mucosa 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 2/3rd 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
submandibular group of lymph nodes .
• Except a small wedge in the symphysis region & the
lower incisors which drain into the submental group of
lymph nodes.
• From the submental group the lymph drains to the
submandibular group of nodes.
• Most of the submandibular nodes ultimately drain to the
jugulo-omohyoid group of deep cervical lymph nodes.
• Few extremely posterior submandibular nodes drain to
jugulo-digastric group 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 mandibular canal is of large size, and runs near
the lower border of the bone; the mental foramen
opens beneath the socket of the first deciduous
molar tooth.
The angle is obtuse (175°), and the condyloid portion
is nearly in line with the body. The coronoid process
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 rami takes 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 coronoid process.
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 mandibular canal
are close to the alveolar border.
3. The angle again becomes obtuse about 140
degrees because the ramus is oblique.
IN OLD AGE

39. APPLIED ANATOMY OF MANDIBLE
1. Parasymphysis region lateral to the mental
prominence is a naturally weak area susceptible for
parasymphyseal fracture. This is because of the
presence of incisive fossa and mental foramen.
2. The body of the mandible is considerably thicker than
the ramus and 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 mandibular condyles renders 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 condyle prevents 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
condylar neck along with the parasymphysis fracture at
the same side of the blow.

41. 6. It is possible to split the ramus of the mandible
in sagittal plane bilaterally thereby correcting
micrognathia this procedure is called sagittal split
osteotomy.
7. Osteomyelitis of the mandible is more
commoner than the maxilla as the maxilla has
rich blood supply.

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