Fallopian tube: From Egg to Blastocyst

Animated sequence showing the passage of the egg from fertilization at the top of the fallopian tube to implantation as a blastocyst in the uterus. This sequence will run repeat itself until the ESC key is pressed.

In IVF the embryos have until recently been transferred to the uterus at the early cleavage stage - i.e. from 4 to 8 cells (day 2 or 3). Current arguments suggest that it might be more physiological to transfer the embryos after they have grown to the blastocyst stage (days 5,6 onwards) when they would normally start to embed. Current culture condition allow the embryos to grow to that stage and randomized trials are in progress to see whether this shows advantage over transfer on day 2 or 3

The blastocyst orientates itself and then embeds in the endometrial ligning of the utersus where the trophoblast cells (those around the periphery) make contact with the maternal blood vessels to form the placenta which will support the embryo/fetus during pregnancy.