Collaborative Resources for
Learning Developmental Biology
Collaborative Resources for Learning Developmental Biology
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Day 19 Trophoblast Development in Sheep
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Rajesh Sharma

Additional Author(s): T.J. Parkinson, P. R. Kenyon, H. T. Blair

Published on SDB CoRe: Nov 14 2012

Organisms: Vertebrates
Tools & Techniques: Microscopy
Early Embryogenesis: Maternal Determinants
Morphogenesis: Cell Shape Changes
Signaling: Morphogens and Gradients
Extraembryonic: Extraembryonic Tissues
Evolutionary Developmental Biology: Developmental Modifications
Organism: Sheep
Stage of Development: Embryo

Object Description

The gestation period of sheep is 150 days. The interaction between the embryo and uterine environment starts very early in pregnancy when the embryo is undergoing rapid cell divisions, implantation, and organogenesis. This section of trophoblast tissue was obtained at Day 19 of conceptus development. Trophoblast binucleate cells (shown by green arrow) are stained by Periodic Acid Schiff’s stain and appear larger than mononucleate cells (shown by red arrow). They first appear at Day 16 of pregnancy in trophoblast tissue and their number increases as gestation advances. They synthesize ovine placental lactogen which modulates transfer of nutrients from dam to fetus. Recent study1 has shown that by Day 19 gestation, trophoblasts of large genotype sheep embryos reared in small genotype uterus have fewer binucleate cells than those reared in large genotype uterus, but there is no difference in their size. In contrast, trophoblasts of small genotype embryos reared in large genotype uterus have more and larger binucleate cells than those reared in small genotype uterus. This indicates a possible mechanism by which the uterine environment regulates the development of conceptus.


1Sharma, R.K., 2010. The effects of uterine environment upon embryonic, fetal, neonatal and post-natal development and glucose metabolism in sheep. Institute of Veterinary Animal and Biomedical Sciences. Massey University, Palmerston North, p.235 (PhD Thesis).

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