GROSS, HISTOLOGICAL AND HISTOCHEMICAL STUDIES ON THE UMBILICAL CORD AND FOETAL MEMBRANES OF GOAT (Capra hircus)
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Date
2023-03
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SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517 502. (A.P.) INDIA
Abstract
The study was conducted on umbilical cord and foetal membranes collected from
gravid uteri procured from 18 non-descript goat breeds with embryo or foetuses of age
groups between 29 to 130 days of gestation. Umbilical cord was a tube like structure that
connected embryo or foetus to the placenta. It was covered externally by amnion that
contained white, irregular projections called as amniotic papillae from 66 to 130 days of
gestation. It contained two umbilical arteries, two umbilical veins and allantoic duct
embedded in mucous connective tissue called as Wharton’s jelly. Mucous connective
tissue of umbilical cord was made of abundant collagen fibers, few elastic and reticular
fibers and various cells like fibroblasts, fibrocytes, mesenchymal cells, mast cells,
lymphocytes, macrophages and plasma cells dispersed in it. Chorion was the outermost
layer and was thinnest compared to allantois and amnion. It contained cotyledons with
intercotyledonary regions between them. In all the groups, the chorion was comprised of
trophoblast layer lined by single layer of uni and binucleated cells underlying
mesenchymal tissue. The chorionic villi were elongated structures that branch extensively
with advancement of age. Allantois was a transparent fluid filled sac that contained two
arms separated by band like structure called isthmus. Allantois was made up of simple
squamous or cuboidal epithelium internally and mesenchyme externally at all ages. Cell
density in mesenchyme of allantois was lesser than amnion. Amnion was the innermost
extraembryonic membrane which was a thin, tough and transparent membrane during all
stages of gestation that covers embryo and outer wall of umbilical cord. It extended from
navel, surrounded the umbilical cord and then completely reflected over the foetus.
Amnion was made up of simple squamous or simple cuboidal epithelium internally and
mesenchyme externally. Mesenchymal tissue of chorion, allantois and amnion contained
mainly collagen fibers with few elastic and reticular fibers with undifferentiated
mesenchymal cells, fibroblast cells, fibrocytes and Hofbauer cells. Placentome was
formed by intimate contact between caruncle from maternal endometrium and cotyledon
from the chorion of the foetus. The number of placentomes ranged from 68 to 166 with
more number of placentomes concentrated in pregnant horn compared to non pregnant
horn. Synepitheliochorial form of placentation was seen as the binucleate cells of
trophoblast epithelium of chorion migrate and fuse with maternal caruncular epithelial
cells and form symplasmic plaques. Amniotic epithelium, amniotic papillae, tunica intima
and smooth muscles in tunica media and tunica externa of umbilical vessels and
epithelium lining the allantoic duct in umbilical cord and also epithelium of chorion,
allantois and amnion showed PAS positive reaction for neutral mucopolysaccharides
whereas connective tissue fibers of tunica media and mucous connective tissue and
mesenchyme of chorion, allantois and amnion showed AB positive reaction for acid
mucopolysaccharides in all age groups. Amniotic epithelium, mucous connective tissue,
connective tissue surrounding allantoic duct and tunica externa of umbilical vessels in
umbilical cord, epithelial lining of chorion, allantois and amnion and cells in the
mesenchyme exhibited bromophenol blue positive reaction for basic proteins.