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From Fertilization to Blastocyst

This time-lapse video shows a human embryo from the time of fertilization, when it is a single cell, until it reaches the blastocyst stage (around five days after fertilization).

At the early stages, the nuclei of individual cells are clearly visible, and viewers can observe the frantic activity of the genetic material in each nucleus as the cells prepare for further divisions. Over the five-day time period, the large cells of the early stages become more and more compact, subdividing their cytoplasm with each successive division. Toward the end of the five-day period, the mass of cells begins to cavitate in the center, producing the blastocyst.

The blastocyst is a sphere of about 150 cells, with an outer layer (the trophoblast), a fluid-filled cavity (the blastocoel), and a cluster of cells on the interior (the inner cell mass).


Used with permission of Ronny Janssens, Quality Manager for the Centre for Reproductive Medicine, Universitair Ziekenhuis Brussel. The movie was filmed with a Nikon BioStation IM, from Nikon Instruments, Inc.

Movie requires the free QuickTime player.