Embryogenesis is a process that entails cell division and differentiation to generate the embryo. Biologically, embryogenesis is initiated in zygotes following the fertilization process. This follows the union between the sperm cell and the egg (Symposium, 2009). There are a series of stages and processes that are involved in early embryo development. The primary stage is the fertilization process which occurs when the haploid egg successfully unites with the sperm cell to generate a diploid zygote. The process is influenced by enzymes and hormones which trigger the chemotactic movement of the sperm cells. The fertilization process is followed by the cleavage stage characterized with mitotic divisions.
The initial blastomeres form gap junctions that are essential for the cleavage that is essential to trigger differentiation. Blastulation progresses after the cleavage to create the blastocysts which form an inner cell mass enclosed in a trophoblast (Ioannou et al., 2014). By the end of the second week, implantation occurs, with the endometrial lining being converted into secretory lining in readiness for the implantation. Trophoplast differentiation follows and is influenced by the hormone levels, progesterone from the corpus luteum playing a key role. The embryonic disc then forms and is characterized with epiblast and hypoblast (Nic-Can et al., 2015). This is followed by the gastrulation process which occurs around the 17th day after fertilization. The other key process that occurs during the early stages is neurulation which initiates the development of neural tissues, and eventually organogenesis.
with any paper
- Ioannou, D., Millan, N., Jordan, E., & Tempest, H. (2014). Global telomere organisation in the 3D human sperm nucleus: a new arrangement and inferences for fertilization and embryogenesis. Fertility And Sterility, 102(3), e111.
- Nic-Can, G., Galaz-Ávalos, R., De-la-Peña, C., Alcazar-Magaña, A., Wrobel, K., & Loyola-Vargas, V. (2015). Somatic Embryogenesis: Identified Factors that Lead to Embryogenic Repression. A Case of Species of the Same Genus. PLOS ONE, 10(6), e0126414.
- Symposium, C. (2009). Embryogenesis in Mammals (1st ed.). Hoboken: John Wiley & Sons.