Download Development of tongue

Development of tongue
the tongue's embryonic origin is derived from all
pharyngeal arches contributing different
components. as the tongue develops "inside" the
floor of the oral cavity, it is not readily visible in the
external views of the embryonic stages of
development.
myogenesis (the development of muscular tissues)
of the masticatory muscles are delayed in
comparison with other muscles and are not
complete even at birth, whereas the development
of tongue muscles proceeds faster and ends at
around birth
Development of tongue begins at about 4th week of (IUL)
due to local proliferation of mesenchyme in the floor of the
mouth one elevation (swelling)appear in the Medline which
is called median tongue or tuberculum
median tongue it arise from endodermal floor of the
pharynx
this followed by two elevations called lingual projections or
(bulges, swelling) distal tongue one on either side of the
median elevation appear on the endodermal aspect of the
mandibular processes
Lateral lingual elevation quickly enlarge merge and fuse with
each other and form large masse
mucous membrane of anterior two third of tongue formed
from this mass.
Along the ventral and lateral margins of this elevation
asulcus forms and deepened to form the linguogingival
grooves.
Floor of the mouth the tongue is separated by down growth
of ectoderm around its periphery ,later on. this down growth
of the ectoderm around the periphery of tongue separates
the tongue from the floor of the mouth.(in this way lingual
sulcus is formed and tongue becomes mobile)
Foramen cecum
Foramen cecum is found just behind the tuberculum
impare.is related to the development of the thyroid
gland .posterior to it ,the hypo brachial eminence is
found ,which has two part
a. Cranial part which give rise to posterior of the
tongue
b. caudal part .give rise to the epiglottis
Tongue muscles originate from the mesoderm. The tongue
muscle develops before masticatory muscles and is
completed by birth.
Masticatory muscles :originate from loose masses of the
mesoderm. These muscles develop late and are not
complete even at birth. Masticatory muscles develop muscle
fibers within the tongue. And these muscles go through the
same developmental changes as other skeletal muscle.
The epithelium of the tongue is at first made up
of single layer of cells, later it becomes
stratified and papillae become evident. The line
of the sulcus terminalis is marked by eight to
twelve circumvallate papillae that develop at 25 months of the intrauterine life.
The mucosa of the dorsal surface of the body of
the tongue develops papillae at eleven weeks of
the intrauterine life.
At birth, the root mucosa becomes pitted by
deep crypts that develop into lingual tonsils,
the completion of which is marked by
lymphocytic infiltration.
Taste buds arise by the inductive interaction
between epithelial cells and nerve cells in the
tongue.
Development of anomalies of tongue
Examples are:
Median rhomboid glossitis: it results from
persistence of tuberculum impair. It is
characterized by a red, smooth zone as seen in
the midline, slightly anterior to the foramen
caecum.
Bifid tongue
it is seen when the two lateral processes of the tongue
are not fused completely. It is very rare
Macroglossia (enlarged tongue):
it is due to an over-development of the tongue.
Microglossia (small tongue):
it is due to an under-development of the tongue.
Ankyloglossia:
due to fusion of the tongue with the floor of the mouth.
Mostly it is partial and very rarely complete
.
Fissured tongue:
in this there are numerous small fissures or grooves on
the dorsal surface of the tongue.