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                                                Embryo (labels) - histology illustration
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                                                Section through ovum imbedded in the uterine decidua. Semidiagrammatic. (After Peters.) am. Amniotic cavity. b.c. Blood-clot. b.s. Body-stalk. ect. Embryonic ectoderm. ent. Entoderm. mes. Mesoderm. m.v. Maternal vessels. tr. Trophoblast. u.e. Uterine epithelium. u.g. Uterine glands. y.s. Yolk-sac. 
 
Histology illustration courtesy of Gray's Anatomy.
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