Embryogenesis (from the ancient Greek ‘émbryon’ meaning ‘unborn womb’ and ‘genesis’ meaning ‘development’) is the early process in the development of an embryo in biology. It is the first stage of germinal development of the fertilized egg (zygote) and occurs in different sequences in all living things.
What is embryogenesis
In humans, embryogenesis begins after fertilization of the egg (fertilization) and occurs over a period of eight weeks. In humans, embryogenesis begins after fertilization of the egg (fertilization) and occurs over a period of eight weeks. During embryogenesis, the predispositions of all the later organs of the fetus develop. However, many organs do not become functional until later. Embryogenesis is a phase in which there is a strong growth of the maturing organism. It is highly sensitive to disturbances and external influences during this time, which explains why the first eight weeks of pregnancy are considered particularly risky. Embryogenesis ends with the onset of fetogenesis, during which, among other things, the further development and functioning of the organs, as well as a steady increase in size and weight, take place. Embryogenesis is also called the embryonic period and is accompanied by a striking transformation of the embryo‘s external shape. Within embryogenesis, a distinction is made between the pre-embryonic phase (1st to 3rd week of gestation), in which three germ layers develop, and the actual embryonic phase, which extends from the 4th to the 8th week and is accompanied by the development of the organ systems. This highly sensitive process takes place with the help of genetic programming and in interaction with environmental factors, which must be in a precisely coordinated balance.
Function and task
Early embryogenesis is the stage in embryonic development in which the young organism develops most rapidly. After the egg and sperm fuse and a zygote is formed, it migrates to the female uterus over a period of three days. During this migration, cell division (furrowing) occurs. Through continuous constriction, a sphere fully filled with blastomeres, called a morula, is formed from the original cell. This particular cell division occurs in very rapid succession. About every eight minutes, a division of the cell nucleus can take place. The formation of the morula is completed on the 4th day of pregnancy. Differentiation of the blastomeres then occurs, with the outer layer of cells henceforth developing into the membranes and placenta, while the inner layer will eventually unfold into the embryoblast, the origin of the eventual embryo. After the cell collection, now called blastocyst, has nested in the uterine mucosa, three germ layers form in the subsequent gastrulation, from which the entire tissue and organ structures of the human being will later develop. In addition, the so-called neural tube, which is the basis of the central nervous system, is formed. A turning point in embryogenesis is the formation of the so-called primitive streak. This can be seen as a thickening on one side of the organism and for the first time reveals a spatial orientation: a longitudinal axis of the fetus has been established. At one end of the primitive streak is the primitive node, from which the head of the embryo will henceforth develop. After this early embryonic development is completed, the second part of embryogenesis follows, the main task of which is organogenesis – the formation of the later organs. During the first two weeks of this developmental phase, the brain, heart, and eyes emerge first. The entire embryogenesis forms the basis for the further development of the fetus. Everything that is established and arranged during its period has multiple effects on the development of the embryo and the entire life of the human being.
Diseases and disorders
During the period of embryogenesis, the risk of possible malformations and diseases is the greatest, since the formation of organs is not yet complete and can be extremely influenced. A variety of different triggers can affect the optimal development of the fetus and are not infrequently the cause of miscarriages.In some cases, these are not even noticed by the woman, so it can happen that a fetus aborts before the woman has even noticed her pregnancy. If the miscarriage does not occur and the harmful influences continue, serious malformations can develop in the fetus. Underdevelopments in the brain region, facial deformities and maldevelopments of the internal organs are the most common malformations. The greatest risk factors for miscarriage or deformity at the stage of embryogenesis are infectious diseases, toxins (such as nicotine) entering the maternal organism, medicines, or harmful radiation. Mothers who consume alcohol during the early stages of pregnancy, for example, risk that their child will suffer from fetal alcohol syndrome. This manifests itself later in the form of growth disorders, characteristically conspicuous facial features or various psychological abnormalities. After the embryogenesis phase, the risk of malformations of the fetus steadily decreases. In addition to the risks that this phase represents for the unborn creature, the first weeks of pregnancy also represent a difficult time for the expectant mother. Since the initial period of pregnancy is associated with strong hormonal changes, about 50 to 90% of women suffer from increased nausea, vomiting and dizziness during this phase. In the course of pregnancy, however, the female hormonal balance settles down again and the complaints decrease in the majority of cases.