A layer of tissue on the outside of a mammalian blastula, supplying the embryo with nourishment and later forming the major part of the placenta.
- ‘The trophoblast eventually forms the placenta, through which the embryo proper receives dissolved nutrients and is cleansed of waste.’
- ‘The placenta derives from embryonic cells called trophoblasts, which form a ball around the cells that ultimately develop into the fetus.’
- ‘A villus has a fibromuscular core with fetal blood vessels and is covered by an epithelium termed the trophoblast.’
- ‘The surface of the sphere is made up of a layer of specialized cells called the trophoblast.’
- ‘When the developing, fertilized egg at the ‘blastocyst’ stage becomes implanted in the lining of the uterus, it develops ‘villi’ - fine, frond-like cellular projections from its outermost layer, the trophoblast.’