ANDY WALKER, MIDLAND FERTILITY SERVICES / SCIENCE PHOTO LIBRARY ANDY WALKER, MIDLAND FERTILITY SERVICES / SCIENCE PHOTO LIBRARY
Light micrograph showing a human blastocyst, the pre-embryo six days post-fertilisation. The blastocyst is a hollow ball of cells with a fluid centre. Most of these cells will form the placenta & membranes, & only a small group (the inner cell mass) form the embryo proper. At this stage the whole is contained within the zona pellucida of the original oocyte. The blastocyst then absorbs water, swelling to stretch the zona pellucida. After a few hours, the zona ruptures & the blastocyst emerges through the hole produced. This image was produced in the course of In Vitro fertilisation research.
Model release not required. Property release not required.