The document provides an overview of the development of the tongue and mandible. It discusses: - The tongue develops from the first, second, third, and fourth pharyngeal arches. Its musculature originates from somites. - The mandible develops from the first pharyngeal arch. Meckel's cartilage provides a template for its growth. Ossification begins around the 6th week of development. - Both the tongue and mandible have intrinsic and extrinsic muscles that are innervated by various cranial nerves. Their growth and development are closely coordinated.

2. TONGUE & MANDIBLE
DR M.VIVEKBHARGAVA
(1st YEAR PG DIPLOMA)

3. TABLE OF CONTENTS
 Recollection of keywords
 Introduction to tongue & mandible
 Growth & development
 Muscles present / related
 Nerve innervationS
 Molecular pathways/genetical
considerations
 Developmental defects/anomalies
 Reviews
 Conclusion

4. KEY WORDS
i. CRANIAL NERVES
ii. TUBERCULUM IMPAR
iii. PIERRE ROBIN SYNDROME
iv. SOMITES
v. PERICARDIUM
vi. ?CONGENITAL & ? DEVELOPMENTAL

6.  PIERRE ROBIN SYNDROME – (or)
sequence in which an infant has a
smaller than normal lower jaw, a tongue
that falls back in the throat & difficulty in
breathing . It is present at birth
 SOMITES – PRECURSOR POPULATIONS
OF CELLS
Sub divided into
a)
sclerotome
b)myotome

7.  PERICARDIUM -the membrane enclosing of an outer
fibrous layer & an inner double layer of serous
membrane
 FIRST ARCH SYNDROME – these are congenital
defects caused by a failure of neural crest cells to
migrate into the 1st pharyngeal arch. They can produce
facial anomalies ex- Treacher collins syndrome, pirre
robin syndrome.

8.  CONGENITAL – is one which is present at/before
birth but is not necessarily inherited i.e., transmitted
through genes
 DEVELOPMENTAL – unusual sequelae of
development . A deviation from normal shape (or) size

9. TONGUE

10. INTRODUCTION
 The Tongue name originated from Latin-Lingua &
Greek – Glossa .
 It is a solid muscular organ situated in the floor of the
mouth.
 Function – it is a complex muscular organ which plays
key role in Mastication , Taste sensation , Articulation &
maintenance of oral health .
 The tongue & mandible have common origins.
 They arise simultaneously from the mandibular arch &
are co-ordinated in their development & growth.
 Which is evident from several clinical conditions .

11.  Initiation /first evidence of tongue development reported
about the 4th week of IUL.
 The tongue’s embryogenic origin is derived from all the
pharyngeal arches contributing different components.
 i.e., from arch1 –oral part of the tongue(ant.2/3rd)
arch2 –initial contribution to surface is lost.
arch3 –pharyngeal part of the
tongue(post.1/3rd)
arch4 –epiglottis & adjascent region.

13. FORM OF THE TONGUE
 ANTERIOR 2/3rd –from two lingual swellings & one
tuberculum impar, which arises from the first branchial
arch ---- this tuberculum impar soon disappears
 POSTERIOR 1/3rd -4 cranial large part of the
hypobranchial eminence i.e., from the 3rd arch.
 POSTERIOR MOST PART – from the 4th arch.

15. Fertilisation Age
(weeks)
Gestational Age
GA (weeks)
Mean Circumference
(mm)
12 14 28
13 15 33
14 16 36
15 17 37
16 18 43
17 19 48
18 20 51
19 21 55
20 22 58
21 23 62
22 24 64
23 25 70
24 26 73

16. MOLECULAR PATHWAYS
 Hedgehog signaling pathways (TGF-β , WNT &
Notch) all play an important role in mediating
appropriate signaling interactions between the
epithelial , CNC & mesodermal cell populations
that are required to form the TONGUE.
 STUDY –Disruption of epithelial Wnt production
by Wls deletion in epithelial cells led to a failure
in lingual epidermal satisfaction & loss of the
lamina propria & the underlying superior
longitudinal muscle in the developing mouse
tongue

17. TONGUE MUSCULATURE
 Tounge muscles originate from the Somites
 Masticatory muscles originate from the
somitomeres
 These muscles develop late & are not complete
even at birth.
 Tongue muscles develop before masticatory
muscles & complete by birth

19. MUSCLES
 I
INTRINSIC
MUSCLES
EXTRINSIC
MUSCLES
1. SUPERIOR
LONGITUDINAL
2. INFERIOR
LONGITUDINAL
3. TRANSVERSE
A. GENIOGLOSSUS
B. STYLOGLOGGU
S
C. PALATOGLOSS

20. INTRINSIC MUSCLES

21. SUP. & INF. LONGITUDINAL MUSCLES
ORIGIN Below the dorsum of the
tongue & lingual septum
Root of the tongue
INSERTIO
N
Extends to lingual artery Apex of the
tongue
ARTERY Lingual artery Lingual artery
NERVE Hypoglossal nerve(xi) Hypoglossal
nerve
ACTIONS Retracts the tongue with
inferior longitudinal muscle
Curls the tip of the
tongue & shortens

22. TRANSVERSE & VERTICAL MUSCLES
ORIGIN Median fibrous septum Dorsum surface of
borders of tongue
INSERTI
ON
Sides of the tongue Inferior surface of
borders of tongue
ARTERY Lingual artery Lingual artery
NERVE Hypoglossal nerve Hypoglossal nerve
ACTIONS Makes the tongue
narrow & elongated
Flattens & broadens
the tongue

23. EXTRINSIC MUSCLES

24. STYLOGLOSSUS & GENIGLOSSUS
ORIGIN Styloid process of the
temporal bone
Arises from the
mental symphysis
INSERTION Inferior surface of borders
of tongue
Dorsum of the
tongue & body of
hyoid
ARTERY Lingual artery Lingual artery
NERVE Hypoglossal nerve Hyoglossal nerve
ACTIONS Retraction & elevation protrusion

25. PALATOGLOSSUS & HYOGLOSSUS
ORIGIN Oral surface of the
palatine aponeurosis
Hyoid bone
INSERTION Sides of the tongue Sides of the tongue
ARTERY Lingual artery Lingual artery
NERVE Vagus(x) Hypoglossal nerve
ACTION elevation depression

28. LINGUAL FRENULUM
 It is a general term for a small fold of integument or
mucous membrane that limits the movements of tongue
 LF is associated with the inferior side of the tongue
 The LF length(if short than normal) & position of
insertion (anterior) can lead to speech disorders & may
affect post natal feeding
 Interestingly it is the prevalence of pain in breast
feeding mothers ,who’s child is with ankyloglossia
 Children with a frenulum length of more than 2cms
doesn’t show these speech problems

30. TONGUE INNERVATION
 TRIGEMINAL NERVE(V) –Lingual branch
 FACIAL NERVE(VII) –Chorda tympani branch
 GLOSSOPHARYNGEAL NERVE(IX)
 HYPOGLOSSAL NERVE(XII) –motor components of
innervated muscles
(xii) –allows protrusion, retrusion & changes in the
shape of the tongue
 Motor units with in the hypoglossal motor system
can be categorized as predominantly fast & fatigue
resistant

32.  Taste buds contain the taste receptor cells, which are
also known as gustatory cells.
 The taste receptors are located around the small
structures known as papillae found on the upper
surface of the tongue, soft palate, upper esophagus, the
cheek and epiglottis.
 The taste receptor cells send information detected by
clusters of various receptors and ion channels to the
gustatory areas of the brain via the seventh, ninth and
tenth cranial nerves.

33. PAPILLA OF TONGUE

34.  The dorsum of the tongue is covered by
“stratified squamous epithelium”.
 It consists of squamous(flattened) epithelial
cells arranged in layers upon a basal
membrane.
 One layer is in contact with the basement
membrane , the other layers adhere to one
another to maintain structural integrity
 There are also 8-12 circumvallate papillae
arranged in an inverted ‘v’ shape towards the
base of the tongue.

35. ABNORMALITIES
i. Ankyloglossia
ii. Microglossia
iii. Macroglossia
iv. Cleft tongue
v. Lingual varices
vi. Fissured tongue
vii. Median rhomboid glossitis
viii. Benign migratory glossitis
ix. Hairy tongue
x. Lingual thyroid nodule

36. ANKYLOGLOSSIA
 Short frenulum length
 Which limits the range of movement of the tongue
 Genetics reasons related to ankyloglossia :-
1) ROR2-related robinow syndrome
2) Oral facial digital syndrome type1
3) Dystrophic epidermolysis bullosa
4) Opitz syndrome
5) Vander woude syndrome

37. MICROGLOSSIA
 Abnormally small tongue
 Recent study has identified cranial neural fibroblast ,
non canonical transforming growth factor β (TGF-β) ,
regulation of FGF & BMP signaling can cause similar
muscle developmental defects.

38. MACROGLOSSIA
 Causes of aquired macroglossia :-
acromegaly,myxedema,amyloidoisis,angioedema
 Clinical features :
noisy breathing , difficulty with
chewing , swallowing , drooling , slurred speech ,
widened interdental space , scalloping/crenations , open
bite/mandibular prognathism , dry/cracked tongue ,
ulceration , secondary infection , hemangioma.

39.  CLEFT TONGUE - Occurs due to lack of merging of
lateral swellings
 FISSURED TONGUE – it’s a malformation manifested
clinically by numerous small grooves on dorsal surface
radiating out from central groove along the midline of
tongue.
 C/F :- grooves & furrows ranges from - 2-6mm
 It is also considered as an sequelae of geogrophic
tongue

42. MANDIBLE
 Name derived from the Latin word “mandibula” which
means jaw bone.
 Mandible is a membrane bone, developed in
relation to the nerve of the first arch.
 It is the longest & strongest bone of the face which
serves for the reception of the lower teeth.
 Consists of a curved horizontal portion i.e., the body
and rami , alveolar process which hosts the primary &
permanent teeth
 The body and rami unite at the angle of the mandible
nearly at right angles.

43. GROWTH OF THE MANDIBLE
 TODD -an increase in size
 MOYERS –quantitative aspect if biologic development
per unit of time.
 DEVELOPMENT – progress towards maturity (todd).
 Growth of the mandible is described in two stages i.e.,
1)Pre-natal growth of the mandible
2)Post-natal growth of the mandible

44. PRE-NATAL GROWTH
 About the 4th week of IUL , the developing brain & the
pericardium form 2 prominent bulges on the ventral
aspect of the embryo.
 These bulges are separated by the primitive oral
cavity/stomodeum.
 The floor of the stomodeum is formed by the
buccopharyngeal membrane , which separates it from
the foregut.
 The pharyngeal are laid down on the lateral & ventral
aspects of the cranial most part of the foregut that lies
in close approximation with its stomodeum.

45.  Mandibular arch forms the lateral wall of the
stomodeum.
 It gives off a bud from its dorsal end which is called
maxillary process.
 It grows ventro-medially , cranial to main part of the
arch , which is now called as the “mandibular process”.
 The mandibular process of both sides grow towards
each other & fuse in the midline.
 They now form the lower border of the stomodeum i.e.,
the lower & lower jaw.

46. MECKEL’S CARTILAGE

47.  It is derived from the 1st brachial arch around 41st – 45th day
of IUL.
 It extends from the cartilagenous otic capsule to the midline /
symphysis & provides a template for guiding the growth of
the mandible.
 A major portion of the meckel’s cartilage disappears during
growth & the remaining part develops into.
1)mental ossicles
2)incus & malleus
3)Spine of the sphenoid bone
4)Anterior ligament of malleus
5)spheno-mandibular ligament

48.  1st structure to develop in the primordium of the lower
jaw is the mandibular division of the V nerve.
 This is followed by the mesenchymal condensation
forming the first branchial arch.
 Neurotrophic factors produced by the nerve induce
osteogenesis in ossification centers.
 A single ossification center for easch half of the
mandible arises in the 6th wk of IUL in the region of the
bi-furcation of the inf. alveolar nerve into the mental &
incisive branches.

49.  The ossifying membrane is located lateral to the
“meckel’s cartilage” & its accompanying neuro -
vascular bundle.
 From this primary center, ossification spreads below &
around the inf. Alveolar nerve & it’s incisive branch &
upwards to form a trough for accommodating the
developing tooth buds.
 Spread of the intramemberanous ossification – dorsally
& ventrally forms the body &ramus of the mandible.

50.  As ossification continues , the meckel’s cartilage
becomes surrounded & invaded by bone.
 Ossification stops at the site that will later become the
mandibular ligula from where the meckel’s cartilage
continues into the middle ear & develops into the
auditory ossicles i.e., malleus & incus.
 The sphenomandibular ligament that extends from the
lingula of mandible to the sphenoid bone also forms a
remnant of the meckel’s cartilage.
 Condylar cartilage develops initially as a separate area
& fuses with the mandibular body around the 4th month
of IUL.

51. ENDOCHONDRAL BONE FORMATION
 Seen only in 3 areas of the mandible :- 1) condylar
2)coronoid
3)mental
region
 CONDYLAR PROCESS :- At about the 5th wk of IUL an
area of mesenchymal condensation can be seen above
the ventral of the developing mandible.
 This develops into a cone-shaped cartilage by about
10th wk & starts ossification by 14th wk.
 It then migrates inferiorly & fuses with the mandibular
ramus by about 4 months.

52.  Much of the cone-shaped cartilage is replaced by bone
by the middle of fetal life but its upper end persisits into
adulthood acting both as a growth cartilage & an
articular cartilage.

53. CORONOID PROCESS :- Secondary accessory cartilage
appear in the region of the coronoid process by about the
10th – 14th wk. IUL.
 This secondary cartilage of coronoid process is
believed to grow as a response to the developing
temporalis muscle.
 The coronoid accessory cartilage becomes intra
membranous bone of the ramus & disappears after
birth.
MENTAL REGION :- On either side of the symphysis , 1 / 2
small cartilages appear & ossify in the 7th month of IUL.
Symphysis ossifies completely during first year of post
natal life.

54. POST NATAL GROWTH OF MANDIBLE
 Of all the facial bones the mandible undergoes the
largest amount of growth post-natally & also exhibits
the largest variability in morphology.
 RAMUS:- The mandible moves progressively posteriorly
a combination of deposition & resorption.
deposition- posterior region
resorption- anterior region.
CORPUS/THE BODY OF THE MANDIBLE:- the
displacement of the ramus results in the conversion of
former ramal bone in to the posterior part of the body of
mandible in this manner the body of the mandible
lengthens

55. Angle of the mandible:-
 Lingual side – resorption takes place on the posterio-
inferior aspect. While deposition takes occurs on the
anterio-superor aspect.
 Buccal side –resorption on ant.-sup. Part
deposition on post.-sup.part
 This results in flaring of the angle of the mandible as
age advances.
Lungual tuberosity:-
 Prominance increased by the presence of a large
resorption field just below it.
 This resorption field produces a sizable depression in
the lingual fossa.

56.  Alveolar process:- develops in response to the
presence of tooth buds. As the teeth erupt the
alveolar process develops & increase in height
by bone deposition at the margins.
 The condyle:-the head of the condyle is covered
by a thin layer of cartilage called the condylar
cartilage which withstands the compression that
occurs at tmj
 Carry-away phenomenon:- the growth of the soft
tissues including the muscles & connective
tissue carries the mandible away from the cranial
base.
 Bone growth follows secondarily at the condyle
to maintain constant with the cranial base
 Growth increases at puberty reaching a peak
12½ - 14yrs ceases around 20years.

60.  CORONOID PROCESS –follows the enlarging ‘V’
principle deposition occurs on the medial surface of the
left & right coronoid process.
 Although additions takes place on the lingual side the
vertical dimension of the coronoid process also
increases.
 Briefly coronoid process has a propellar like twist, so
that its lingual side faces 3 directions i.e., posteriorly,
superiorly & medially.

61.  OSSIFICATION AROUND THE NERVE :-ossification
grows medially below the incisive nerve & then spread
upward b/w the nerve & meckel’s cartilage & so the
incisive nerve is contained in a trough (or) a groove of
bone formed by the lateral & medial plate which are
united beneath the nerve
 At the same stage the notch containing the incisive
nerve extends ventrally around the mental nerve to form
the mental foramen

62.  FORMATION OF OSTEOBLAST IN BRIEF :-
at around 36 – 38 days of IUL there is
ectomesenchymal condensation.
Some mesenchymal cells enlarge & acquire a basophilic
cytoplasm & form osteoblasts.
These osteoblasts secrete a gelatinous matrix called
osteoid &results in ossification of an osteogenic
membrane.

63. MUSCLES OF MASTICATION

66.  Muscular component of the branchial arch form many
straiated muscles in the head & neck region.
 Muscles of mastication derived from the first branchial
arch.
 Develops from intra uterine embryonic mesoderm.
 Muscle tissue develops from the embryonic cells called
myoblast.
 Actions of muscles of mastication:- elevation ,
depression , rotation & gliding movements of the
mandible.
 Elevators :- masseter , temporalis , medial pterygoid.
 Depressors :- lateral pterygoid , mylohyoid , digastric &
geniohyoid.

68. AGE CHANGES IN THE MANDIBLE
 At birth :-
 The body of the bone is a mere shell.
 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.

69. 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.
 and by thickening of the sub dental portion
which enables the jaw to withstand the powerful

70.  the alveolar portion is the deeper of the two,
and, consequently, the chief part of the body
lies above the oblique line.
 The mandibular canal, after the second
dentition, is situated just above the level of
the mylohyoid line.
 mental foramen occupies the position usual
to it in the adult. The angle becomes less
obtuse, owing to the separation of the jaws
by the teeth; about the fourth year it is 140°.

71. ADULTHOOD:-
 The alveolar and subdental portions of the body
are usually of equal depth.
 The mental foramen opens midway between the
upper and lower borders of the bone, and the
mandibular canal runs nearly parallel with the
mylohyoid line.
 The ramus is almost vertical in direction,
 the angle measuring from 110° to 120°.

72. Old age:-
 The bone becomes greatly reduced in size, for with the
loss of the teeth the alveolar process is absorbed.
 Consequently, the chief part of the bone is below the
oblique line.
 The mandibular canal, with the mental foramen opening
from it, is close to the alveolar border.
 The ramus is oblique in direction.
 The angle measures about 140°.
 The neck of the condyle is more or less bent backward.

74. FEATURES IN CHILDREN IN ADULT IN OLD AGE
Mental
foramen
Present close
to the inferior
border of the
body
Present
midway
between the
upper and
lower borders
of the body
Present close
to the upper
border
Angle of
mandible 140° 110° 140°
Relationship
between
condylar and
coronoid
processes
Coronoid
process above
the level of
condylar
process
Condylar
process
projects above
the level of
coronoid
process
Coronoid
process
projects above
the level of
condylar
process
Mandibular
canal
Runs near the
lower border
Runs parallel
with the
mylohyoid line
Runs close to
the upper
border

75. POTENTIAL DISTURBANCES OF NORMAL JAW
DEVELOPMENT
 Develops predominantly during embryonic period from
4th – 8th week(critical time)
1. Failure of the neural crest cells to form from the
margins of the neural tube.
2. Slowed migration of crest cells away from the neural
tube
3. Defective mitotic division of neural crest cells
4. Increased neural crest cell adhesion
5. An unsually high rate of neural cell death
6. A failed epithelial mesenchymal interaction in either
the maxilla(or) mandible prominences , this prevemts
bone cell differentiation.
7. Defect of the influence of related nerve , muscles /

76. ABNORMALITIES
 AGNATHIA
 MICROGNATHIA
 MACROGNATHIA
 FACIAL HEMIHYPERTROPHY
 PAGETS DISEASE
 CHERUBISM
 MANDIBULAR DYSOSTOSIS
 TORUS MANDIBULARIS
 STAFNE’S DEFECT

79. AGNATHIA:- ( Hypoplasia / absence of
mandible)
 Partial absence of mandible is ore common
 Entire mandible on one side may be missing or
more frequently only the condyle or the entire
ramus.
 This is believed to be due to failure of migration
of neural crest mesenchyme into maxillary
prominence at the 4th – 5th week of gestation.

80. MICROGNATHIA :- this condition
results may be from congenitial or aquired .
 Congenital –associated with congenital
heart disease & pierre robin syndrome
 Aquired –syphilis(IU CONDITIONS) ,
Chromosomal abnormalities -49 ,
xxxxxsyndrome , chromosome 8
recombinant syndrome, turner’s
syndrome , trisomy18.

81. MACROGNATHIA :- Both jaws are get affected.
Associated with paget’s disease of bone , acromegaly ,
leonitiasis ossea.
FACIAL HEMIHYPERTROPHY :- it is an rare
developmental disorder often affects right side mostly.
Types:- simple, complex , hemifacial.
 Enlargement is more accentuated at the age of 6 &
continued till the overall growth ceases
 Premature shedding of primary teeth
 Microglossia
 Roots of teeth are predominantly enlarged but may be
short.

82. PAGET’S DISEASE :- chrecterised by excessive
growth & abnormal remodelling of bone.
 results in bone which are weak , enlarged & extensively
vascularized.
ETILOGY:- unknown , may be evidence of genetic link.
 Perticularly in the skull large circumscribed areas of
radiolucency may be present which is termed as
“osteoorosis circumscripta”
MANDIBULAR DYSOSTOSIS:- charecterised by
defects of structures arising from 1st & 2nd branchial
arches .
 Atosomal dominant

83.  CHERUBISM:- AUTOSOMAL DOMINANT
 Facial appearance similar to plump cheeked (cheubism
like face).
 Lesions which are firm & non tender to palpate.
 There may be a displacement (or) rotation of teeth.
 Premature exfoliation and delayed eruption is noticed.
 TOROUS MANDIBULARIS :- more common
defect , seen in premolar areas.(just above the
mylohyoid line)
 STAFNE’S DEFECT:- focal concavity of the
cortical bone on the lingual surface of the mandible.

85. STEM CELLS IN TONGUE & MANDIBULAR
REGENERATION

87. What is the Link between Tongue
Tie, TMJ Disorder and Sleep
Apnea?
How Does Tongue Tie Effect
Jaw and Airway
Development?

88. CONCLUSION
 The tongue and mandible are developed
together from the 1st banchial arch which
undergo different stages of development to
attain the normal size and shape to perform the
normal physiological functions.
 Bmp signaling pathway , Wnt and Notch
pathways play crucial role in normal
development of tongue and mandible
discrepancies and alterations in these genetic
pathways will results in abnormal development
of tongue and mandible.

89. REFERENCES
 Ten cate’s oral histology , development , and function
– 7th edition
 Orban’s oral histology and embryology -12th edition
 Baggiolini A, Varum S, Mateos JM, Bettosini D, John
N, Bonalli M, et al. Premiratory and migratory neural
crest cells are multipotent in vivo. Cell Stem Cell.
2015; 16:314–322. [PubMed: 25748934]
 Human embryology – I.B. singh-11th edition
 S.I.balajhi – orthodontics the art and sciences -6th
edition
 Grabar TM :orthodontics : principles and prectice.
 Soo Jeong Hong · Bong Geun Cha, Yeon Sook Kim ·
Suk Keun Lee Je Geun Chi

90. THANK YOU