When an embryo acts as a rebel

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Embryonic development is an extremely fascinating process.  Reflecting on it calmly, it is incredible that from the union of two nuclei of the (ovum and sperm), a complex living being arises with the potential to become a totally autonomous creature.  All the mechanisms that orchestrate this process, from the  in the endometrium to the development of tissues and organs, seem to be calculated to the millimeter.  However, biology is not perfect and can sometimes make blunders.

Under normal conditions, the oocyte and the sperm meet in a region of the fallopian tubes relatively close to the ovary, known as the  .  Once fertilization has occurred, the resulting embryo in the morula Country Email List phase moves slowly towards the uterine cavity while its cells differentiate into a  (the embryo itself) and a  (precursor of the placenta). Normally in the endometrium occurs around six or seven days after fertilization. When implantation occurs outside the uterine cavity, what is known as an ectopic pregnancy has .