The surface anatomy and histology of the adult tongue of domestic animals and
its papillae is described in numerous textbooks of Histology (Fawcett
and Raviola, 1994; Eurell et al., 2006). Numerous
research studies investigated morphogenesis of lingual papillae in various animal
species (Ahpin et al., 1989; Tichy,
1992; Fujimoto et al., 1993; Iwasaki
et al., 1996a; Kulawik, 2005a, b)
and human (Witt and Reutter, 1997). The available reports
were entirely concerned with adult structures of the tongue and papillae much
less has been written about the prenatal development of the lingualpapillae
This research described the light microscopic features of the development of the lingualpapillae at the foetal stage in the one-humped camel (Camellus dromedaries ), an important breed of camel in Iran. The study will also add to the existing information on the morphogenesis of the tongue in camels.
MATERIALS AND METHODS
Tongues used for this study were obtained from 25 foetuses (5 specimen from
each month). Camel uteruses were gathered from slaughter house in yazd province
after dissecting the uteruses, the age of foetuses were meagered by crl formula
(using crown-to-rump length), (age of foetus) = crl+23.9/336, according to McGeady
et al. (2006). The tongue tissues were fixed in Bouins fluid,
dehydrated in graded series of ethanol, cleared in xylene and embedded in paraffin
wax. The blocks of tissues of tongue from apex, middle and root of the tongue
were sectioned in transverse and longitudinal planes of the dorsum of the tongue.
The slides were stained with hematoxylin and eosin. Selected sections were photographed
with photomicroscope and the observations captured on a Laptop Computer. The
morphological features were noted.
RESULTS AND DISCUSSION
In the foetuses of about 60 days old, the sections taken from the dorsum of the apex and the body of tongue was covered by 4-6 layers of epithelial cells. The cells at the basal layer have large oval or round nuclei, while the apical cells consisted of lower cells, their nuclei being flattened. A well defined basement membrane was apparent.
Underlying it is the mesenchymal tissue with cells having oval nuclei and some
amount of cytoplasm (Fig. 1). Some of the tongues of the foetuses
of about 60 days old showed epithelial thickenings on the dorsum and in the
apex of the tongue, the highest concentration being at the apex of the tongue.
days epithelial thickning (Ep) mesenchyime (MM) , H and E x480
five days of papillae (Rd), muscle cells (Ms), H and E x100
These thickenings probably were early rudiments of some lingual papillae.
In the foetuses of about 75 days old, there was further maturation of the epithelium. The dorsum of the apex, the body and root of the tongue showed rudiments of filiform and fungiform papillae, which was quite apparent. The arrangement of the rudiments of filiform papillae is similar to the distribution of epithelial thickenings (Fig. 2). The epithelial thickenings showed that cells are in about 10-12 layers, with the basement membrane very apparent, which rested on well defined lamina propria. The lamina propria of the mucous membrane formed protrusions, constituting the connective tissue core of the developing lingual papillae. In the foetuses of about 90 days old, there was further maturation of the papillae; primordial of filiform, vallate and fungiform were very apparent. There were marked differences from the previous age group. Collagenous fibres and blood vessels were present in the lamina propria (Fig. 3-5). The vallate papillae showed maturation and folding of the epithelium.
days developing fungiform papillae, H and E x120
days developing fuliformpapillae, H and E x120
days developing vallatepapillae connective tissuecore (arrow), H and E
In the 105 days old foetuses, the lingual papilla looked continued to mature with some rudiments of taste buds apparent on the fungiform papillae The presence and maturation of the filiform papillae was also apparent (Fig. 6 and 7). Muscle fibres and connective tissues look well developed.
hundred and five days fungiform papillae and rudiment of taste buds (arrow),
H and E x120
hundred and five days maturing fuliform papillae, muscle fiber (arrow),
H and E x480
In 120 days old foetuses there was further maturation of the papillae and it showed filiform, fungiform and vallate papillae, with the lamina propria showing full differentiation (Fig. 8), taste buds were well developed and showes basal cell, supporting cell and neuroepithelial cell (Fig. 9). Muscle bundle, collagenous fibres, blood vessels, nerves bandle and gustatory glands were well developed (Fig. 10). The observations under light microcopy madeit possible to following the developmental changes in the mucous membrane of the tongue from day 60-120 of prenatal life in camel. The study focused on the development and morphology of primordial some of the lingual papillae.
The observations were made in sections of specimen in median, transverse and dorsal planes. It was observed that at 60 days old foetal life, the epithelium covering the dorsum of the examined apex, body and root the tongue have about 4-6 layers of the epithelium, showing thickening of the epithelium. Rudimentary evidence of future papillae formation was observed at this age. The mesenchymal tissue was located under the epithelium, which is found on a well-defined basement membrane.
hundred and twenty days well-developed vallatepapillae and tastebuds (arrow),
H and E x48
hundred and twenty days well-developed fungiform papillae and tastebud
cell with tastepore (arrow), H and E x480
hundred and twenty days well-developed nerve bundle and blood vessel (arrow),
H and E x120
The lamina propria of the mucosa was scant. The 75-105 days old foetuses showed
apparent primordial of different papillae, with additional thickening of the
epithelium. The observed thickenings represent the first forms of primordial
of fungiform and filiform papillae. Descriptions of the development of lingualpapillae
of mouse, rat and human has shown that early developmental stage of dome shaped
structures found in the surface of the tongue were primordial of fungiform papillae
(Iwasaki et al., 1996b, 1997;
Witt and Reutter, 1997).
Skeletal muscles fibers, blood vessels and some serious gustatory glands were
well developed for 105 days old foetuses. The observations of Cho
et al. (2005) in foetuses and neonatesof Korean native goat (Capra
hircus) shows that skeletal muscle and some serious gustatory glandswere
fully developed in 90 days old. In this study, the development of the filiform
and fungiform papillae apparently started about 105 days of foetal life.
The studies of Iwasaki and Kumakura (1994) showed that
the dorsal epithelium of the tongue in rats at the middle or late period of
gestation has no rudiments of filiform papillae. In contrasts, the rudiments
of filiform papillae are clearly recognizable in the dorsal epithelium of the
tongue of newborn rats just before birth; this morphogenesis of the filiform
papillae of rats seems to occur rapidly during only 2 or 3 days, just before
birth in parallel with keratinization of epithelium. It appears that different
factors affect the morphogenesis of rudiments of lingual papillae.
Thus agents such as growth factors and hormones (Iwasaki
et al., 1997) should be examined for the role in different stages
before and after birth to clarify the mechanism of morphogenesis of lingual
papillae and differentiation of cells with different degrees of keratinization.
The tongue is found in all vertebrates except fishes and some amphibians and
the undulation as of the dorsal lingual surface are recognizable as a common
feature of the tongues of most animals from amphibian to mammals (Iwasaki
and Kamakura, 1994; Iwasaki et al., 1996a,
b, 1997). Among reptiles (Iwasaki
and Kamakura, 1994), the keratinization of lingual epithelium is to adapt
to dry land from fresh-water environment. Igbokwe and Okolie
(2009) shows that the dorsum of the tongue of the prepubertal (Red Sokoto
goat) is lined by keratinized stratified squamous epithelium.
The superficial cells had polygonal shape with distinct bodies. Similar features
were reported in horse (Chamorro et al., 1986),
mouse (Watanabe and Ogawa, 2007).
According to Farbman and Mbiene (1991), there is an
intimate relationship between the feeding habits and the development of the
vallate papillae. The findings showed that the connective tissue of vallate
papillae present a cen-tral groove surrounded by connective tissue papillae
with different height.
There are significant complex changes during the development of the mucous membrane of the tongue and its papillae during the period from day 60-120 of prenatal period, which is continued in the postnatal life.