Saturday, June 17, 2023

Embryo become fetus in.. 3rd month

Embryo become fetus in:

  • a- 1st week
  • b- 1st month.
  • c- 2nd month.
  • d- 3rd month. ***
The embryo and the fetus are the field of action of embryology, a discipline that studies the organism in formation, from fertilization to birth.


An embryo is an organism under development, from the first division of the zygote (the fertilized egg) to the formation of the main organs. In the human species, this period lasts eight weeks (which corresponds to ten weeks of amenorrhea). After this date, and until delivery, the embryo becomes a fetus. The implantation of the embryo in the uterus is done after one week.
It should be noted that the period during which an abortion is authorized in France, namely 14 weeks of amenorrhea, which corresponds to 12 weeks of pregnancy, does not only concern the embryo, but also the fetus. And it is easy to understand that opponents of abortion do not admit that a fetus of 11 weeks of life is not considered a person, and therefore likely to be the subject of an abortion, then that a fetus of 13 weeks would already be a human being, to be absolutely respected.
In the context of in vitro fertilization (IVF), embryos are artificially produced outside the body of women. The hormonal stimulation of the ovaries of the infertile woman makes it possible to obtain several oocytes which will be collected by echo-guided puncture in an operating room, under local or general anesthesia. They are then put in contact with the sperm of the donor (the spouse if he is fertile).
Two techniques are possible: classical IVF, in which the oocyte is in direct contact with spermatozoa, and IVF ICSI (intracytoplasmic microinjection of a spermatozoon), a technique in which a single sperm is introduced to the spermatozoa. inside each oocyte. The oocytes thus fertilized by one or the other of these two techniques are then cultured, and the embryos thus obtained are selected for their transfer into the uterus via its cervix: it is the transfer of embryos. This transfer generally concerns 1 to 3 embryos; the supernumerary embryos can be frozen for later use by the infertile couple, for new attempts during the legal five-year period: this is the freezing of embryos.
If the couple who had the embryos frozen does not need them anymore, there are several possible options: ask for the stopping of conservation; to give the embryos to research, or to give them to an infertile couple in the framework of the PMA (medically assisted procreation), officially called AMP (Medically assisted procreation): it is the donation of embryos, which is practiced under the aegis of the Biomedicine Agency. For the couple that receives the embryos of a donor couple, this technique is called the reception of embryos.


The fetus is the stage of intrauterine development that succeeds the embryo and results in the birth of a newborn. The transition from embryo to fetus occurs when organogenesis (formation of tissues and organs) is completed, ie at the end of the 8th week. However, at this stage the genitals are not yet differentiated, which does not allow to know the sex of an 8 weeks fetus.
The adjective corresponding to fetus is fetal: we speak for example of fetal malformations.
These fetal malformations can be due to three types of causes: intrinsic (or constitutional), extrinsic (or environmental), and multifactorial. The first concerns malformations of genic or chromosomal origin (such as trisomies). The second includes infectious (toxoplasmosis) and toxic (thalidomide) causes.
We speak of fetal malformations, and not of embryonic malformations, because these generally lead to a spontaneous abortion ("miscarriage"), and are therefore not observed.
We will pay attention to the pronunciation: the ligature (the grapheme) "œ" is pronounced here as an "é" and not as an "eu".

Embryogenesis and organogenesis:

The medical discipline which studies embryogenesis, in other words the organism in formation, embryo then fetus, from fertilization to the birth of an autonomous living being, is called embryology. There is no "fetology".
Organogenesis is the period of formation of tissues and organs in the embryo, that is, in the initial phase of embryogenesis. The end of organogenesis defines the transition from the embryonic stage to the fetal stage, ie at the end of the 8th week of pregnancy.
Organogenesis is the process of organ formation from the three basic embryonic layers of ectoderm, mesoderm and endoderm.
Schematically, the ectoderm (outer leaflet) gives rise to the epidermis (the skin) and the neuroderm (the nervous system); the mesoderm (middle layer) with skeleton, muscles and vessels; the endoderm (internal leaflet) to the digestive tract and the respiratory system.