In order to understand how the process of fertilization and the birth of a new life takes place, you need to familiarize yourself with the basic concepts. It is necessary to understand what zygote is. And also to answer other questions about how it is formed, what special features it has, what are the stages of its further development, what can prevent it.
So, let's start from the beginning, with the answer to the first question. What is a zygote? This is a cell that is formed by the fusion of two parent germ cells in a process called fertilization. It is characteristic of heterogeneous organisms, serves to multiply them. Living creatures that form zygotes include not only humans and animals, but also many plants and fungi. The term was introduced by the German botanist E. Strasburger at the end of the 19th century.
Having understood what a zygote is, we recall what characterizes the cells that form it. Sex cells, or gametes, are produced by special organs (genital), they are characterized by the presence of a single (haploid) set of chromosomes. As we already understood, the formation of a zygote occurs as a result of combining two gametes, which means that it contains a double (diploid) set of DNA carriers. A unique cell that gives rise to a new organism, according to scientists, is totipotent.
That is, it is able to give rise to absolutely any cell in the body. What else is interesting about this cell structure? At first, the zygote does not divide like a normal cell. There is no growth stage before the divisions, and as a result, each subsequent daughter cells will be smaller than the previous ones. As a result of successive crushing, the
fetal egg becomes like a mulberry.
If we consider the entire process of development of the embryo as a whole, then we can answer the question of what a zygote is, as follows. It is one of the stages of its development. In this case, gametes are considered the first stage, and subsequent stages are already characterized by successive changes in the zygote. This is what successive levels of germinal differentiation look like. The next stage after the zygote is morula (does not have a cavity in the composition), followed by a blastula (single-layer embryo), gastrula (three-layer embryo), and finally, neurula, which gradually passes into organogenesis.
By the way, we note an interesting point: the zygote stage for a living organism may well drag on. This happens with fungi and algae. After fertilization and the formation of a diploid cell, it becomes dormant and persists for a long time. In this case, this cell is called a zygospore. In humans, the rest period is only thirty hours. At this time, the future embryo moves along the fallopian tube into the uterus, where over time,
implantation of the fetal egg into the mucosa will occur. Negative factors such as mutations at the level of individual genes or entire chromosomes, a woman's use of alcohol, drugs, certain medications, smoking, and viral diseases can disrupt the normal course of this process and the further development of the zygote.