PROFESSORS P.M. MOTTA & S. MAKABE / SCIENCE PHOTO LIBRARY PROFESSORS P.M. MOTTA & S. MAKABE / SCIENCE PHOTO LIBRARY
Embryo. Coloured scanning electron micrograph of a sectioned human ovary of an embryo 9-10 weeks after fertilisation. The central part (blue) is called the medulla; it is surrounded by a cortical area (pale red) and by a surface epithelium (orange). Previously to this stage the medulla is occupied by clusters of primitive germ cells, known as sex cords, which have here disappeared and are replaced by a vascular stroma. The surface epithelium of the ovary gives rise in the 7th week to a second generation of sex cords, the cortical cords, which contain the final set of germ cells. Magnification: x170 at 6x7cm size.
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