Growth and Development of Tongue and Salivary Glands

GROWTH AND
DEVELOPMENT OF TONGUE
AND SALIVARY GLANDS

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

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CONTENTS
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INTRODUCTION
DEFINITION OF GROWTH AND DEVELOPMENT
ANOMALIES OF TONGUE
DEVELOPMENT OF SALIVARY GLANDS
ANOMALIES OF SALIVARY GLANDS
PROSTHODONTIC CONSIDERATATIONS
SUMMARY
REFERENCES

Introduction
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Tongue is a muscular organ in the floor of the
mouth associated with a function of taste,
speech, mastication and deglutition.
The tongue also influence the path of eruption of
teeth.
The salivary glands are important organs of oral
cavity which produces saliva, essential fluid
required for normal mastication, swallowing and
digestion.
Hence it is essential to study the growth and
development of tongue and salivary gland.

Definition of growth:
 Krogman : Increase in size, change in proportion
and progressive complexity.
 Todd: An increase in size.
 Moyers: Quantitative aspect of biological
development per unit time.
Definitions of development:
 Todd: Development is progress towards maturity.
 Moyers: Development refers to all the naturally
occurring unidirectional changes in the life of an
individual from its existence as a single cell to its
eloboration as a multifactorial unit terminating in
death. Thus, it encompasses the normal sequential
events between fertilization and death.


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During the early 4th week of I.U.L. the lateral part
of mesoderm of ventral foregut region becomes
segmented to form a series of 5 distinct bilateral
mesenchymal swellings called as pharyngeal
arches.
Pharyngeal clefts: Arches are seperated by
deep grooves called pharyngeal clefts.
Pharyngeal pouch: are outpocketings appearing
along the most cranial part of foregut.


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

Tongue arises from the ventromedial wall of the
primitive oropharynx from the inner lining of the
first four branchial arches.
Development of tongue can be studied under
the following headings
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Anterior 2/3rd (or the body of tongue)
Posterior 1/3rd(base of the tongue)
Musculature and connective tissue
Papillae and taste buds.
The nerve supply

Anterior 2/3 of the tongue
rd



During the 4th week of IUL, paired lateral swellings
appear on the internal aspect of the 1st brachial arches
Tuberculum impar is a median
eminence whose caudal end has a pit called the
foremen caecum



These lateral swellings rapidly enlarge, merge with each
other and overgrow the tuberculum impar to form the
body of the tongue



A U shaped sulcus, the linguogingival groove develops in
front of the oral part, which allows it to be free and highly
mobile except at the region of the lingual frenum where


Posterior 1/3 of the tongue
rd

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The base of the tongue is initially indicated by two
midline elevations that develop caudal to the foremen
caecum
The copula
The hypobrachial eminence
As the tongue develops, the hypobranchial
eminence,overgrows the second branchial arch to
become continous with the body of the tongue. The
site of union b/w the the body and base of the tongue is
delineated by a V shaped groove, called the sulcus
terminalis.

Musculature and connective tissue


Branchial arch mesenchyme forms the
connective tissue and the lymphatic and
the blood vessels of the tongue


Tongue musculature`


During the 5th to 7th
week of the IUL, 3-4
occipital myotomes,
migrate anteriorly to
form the musculature
of the tongue.


Papillae of the tongue


Papillae are projections of mucous membrane
on the dorsum of the tongue
Circumvalate papillae
Fungiform papillae
Filliform papillae
Foliate papillae


Taste buds


Taste buds are located on the dorsum of
the tongue and are associated with the
papillae
Taste buds appear around 8th week of IUL
Taste buds arise by inductive interaction
b/w the epithelial cells and the invading
gustatory nerve cells


Nerve supply of the tongue


Development of tongue from the branchial arch explains
its nerve supply
Sensory supply
Ant 2/3rd-Lingual nerve for general sensation.chorda
tympani for the special sensation
Post 1/3r Glossopharyngeal nerve
Posterior most part -vagus nerve
Motor supply
All the intrinsic and extrinsic muscles except the
palatoglossus are supplied by the hypoglossal nerve.
Palatoglossus –pharyngeal plexus


Arterial supply:
It is chiefly derived from the lingual artery a branch of
external carotid artery. The root of the tongue is also
supplied by tonsillar and ascending pharyngeal artery.
Venous drainage:
The deep lingual vein is the principal vein of the tongue.
Lymphatic drainage:
The tip of the tongue drains into submental nodes. The
remaining part of the anterior 2/3rd drains into the
submandibular nodes. The posterior 1/3rd of the tongue
drains into jugulo-omohyoid nodes

Structure of the tongue
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
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The bulk of the
tongue is made of
muscles
Intrinsic muscles
Extrinsic muscles






The oral part of the
dorsum of the tongue has
numerous papillae
associated with the taste
buds.
The pharyngeal part of
the dorsum of the tongue
is rich in lymphoid
follicles that is collectively
called the lingual tonsil.
Mucous glands are also
present.



The inferior surface of the
tongue shows the
frenulum linguae,deep
lingual veins and the plica
fimbriata




The entire tongue is in the mouth at birth .Its
post 1/3rd desends into the pharynx by the age of
4yrs. The tongue normally doubles in
length,breadth and thickness from birth to
adolesence reaching maximal size at about
8yrs.


ANOMILIES OF THE TONGUE
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Aglossia
Microglossia
Macroglossia
Bifid tongue
Ankyloglossia
Lingual thyroid
Fissured tongue
Median rhomboid glossitis

ANKYLOGLOSSIA


LINGUAL THYROID


FISSURED TONGUE


MEDIAN RHOMBOID GLOSSITIS


Development of
salivary glands

DEVELOPMENT OF SALIVARY GLAND


All salivary glands show a similar pattern of development
They originate from oral epithelial buds invading the
underlying mesenchyme.



The origin of epithelial bud is belived to be ectodermal in
parotid and minor saliavary gland and endodermal in
submandibular and sublingual glands.



The connective tissue stroma and blood vessels form
from the mesenchyme


GLAND

ORIGIN

I.U.LIFE

PAROTID GLAND

CORNERS OF THE
STOMODEUM

6TH WEEK

SUBMANDIBULAR
GLAND

FLOOR OF THE
MOUTH

END OF 6TH WEEK

SUB LINGUAL
GLAND

LATERAL TO
SUBMANDIBULAR
PRIMORDIUM

8TH WEEK

MINOR SALIVARY
GLAND

BUCCAL
EPITHELIUM

12TH WEEK




STAGES OF DEVELPOMENT



STAGE I:
Bud formation :Induction of
oral epithelium by underlying
mesenchyme




STAGE -II
Formation and
growth of epithelial
cord.




STAGE III: Initiation
of branching in
terminal parts of
epithelial cord and
continuation of
glandular
differentiation




STAGEIV:
Dichotomous
branching of
epithelial cord and
lobule formation


STAGE V:Canalization
of presumptive
ducts.


STAGE VI:
Cytodifferentiation


Serous acini

Mucous acini


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Terminal tubules – intercalated ducts
Striated ducts
Intracalated ducts
Myoepithelial cells
Full differentiation of functional secretory
components is apparent at birth but its not
complete until the onset of solid diet and the
presence of masticatory stimuli

Types:


MAJOR SALIVARY GLANDS
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Parotid gland
Submandibular gland
Sublingual gland

MINOR SALIVARY GLANDS
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Buccal
Labial
Lingual
Palatine
Glossopalatine


GLAND

LOCATION

DUCT

SECRETION

Parotid

Ant to the
Stensons duct
external acoustic
meatus

Purely serous

Submandibular

Submandibular
triangle

Whartons duct

Predominantly
serous

Sublingual

Floor of the
mouth

Bartholins duct

Predominantly
mucous

Minor salivary
glands

Beneath the
epithelium

Directly into the
mouth


Nerve supply


Developmental anomalies
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Aplasia
Hyperplasia
Atresia


Prosthodontic considerations


Tongue plays an important role in the stability of lower
denture.
Macroglossia – Stability of the denture is
reduced,hence
Surgical
trimming is indicated
Microglossia –
Inadequate lingual seal.
Bifid tongue
- Surgical reconstruction is required.
Ankyloglossia – Poor registration of the lingual
seal.
Frenectomy is indicated.
Aplasia Denture produces
soreness and irritation
Lack
of retention of the denture



Tongue position is important to the prognosis of
mandibular denture:



Wright classification of tongue position:



Class I : The tongue lies in the floor of the mouth with
the tip forward and slightly below the incisal edges of the
mandibular anterior teeth. Class I position is ideal for
construction of mandibular denture.



Class II: The tongue is flattened and broadened but the
tip is in a normal position.



Class III: The tongue is retracted and depressed into the
floor of the mouth with the tip curled upward, downward
or assimilated into the body of the tongue.

SUMMARY


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The tongue develops from the first 4
branchial arches.
Salivary gland originate from the oral
epithelial buds invading the underlying
mesenchyme.


REFERENCES


Chaurasia B.D. – Human Anatomy, 3rd Edition, 1996



James K.Avery, ‘Oral Development and Histology’, ed.1,Balteimor,
1990, B.C.Decker.
Keith L. Moore – Clinically oriented anatomy. 3rd edition.
Moore & Persaud – The Developing Human, Clinically Oriented
Embryology, 5th Edition, 1993.
Murray Brooker – Clinical embryology: A color atlas and text.
Shafer W.G. – Text Book of Oral Pathology, 4th
Edition, 1983

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Sperber G.H. – Craniofacial Embryology, 4th Edition, 1989.
Tencate A.R. – Oral Histology, 3rd Edition, 1989
Sheldon Winkler – Essentials of complete denture prosthodontics.
2nd edition.


Growth and Development of Tongue and Salivary Glands

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