1
These were produced from a single fertilized ovum, in laboratory conditions.
2
Ectopic pregnancy involves the fertilized ovum implanting on any tissue other than the endometrial lining of the uterus.
3
The uterus becomes gorged with blood periodically, to provide an enriched soil for the perhaps to be fertilized ovum to plant itself.
4
From the fertilized ovum at the top there is a continuous cell development, with differentiation represented in the cell groups of the bottom row.