Fertilization and implantation of the embryo are the key moments for Human Prenatal Development and these events occur during the First Week of Gestation Hello! Welcome or welcome to my YouTube channel, this time we are going to talk about the phenomena and changes that occur during the First Week of Gestation in an easy, fast and simple way. If this is the first time that you are studying these topics, I invite you to see my Introduction to Human Embryology video so that you take into account the basic concepts that must be taken when studying this science.
For the first week to occur, the first thing that must be there is Fertilization and What is Fertilization? It is the process by which the male and female gametes fuse. The male gamete will be the sperm and the female gamete will be a secondary oocyte.
When these two unite, fertilization occurs and this occurs on the first day . How long does it last? Approximately 24 hours and where is the place?
Usually in the ampulla of the uterine tube or fallopian tube The result of fertilization will give rise to a Zygote and thanks to this zygote life arises This zygote has 46 chromosomes resulting from the 23 chromosomes that the sperm provides and another 23 due to the secondary oocyte , therefore, it is a diploid cell and it will be surrounded by the Zona Pellucida On the second day Segmentation occurs, the zygote undergoes a series of mitotic divisions that increases its number of cells The first division of the zygote takes place approximately 30 hours after fertilization and the cells that result from this division are called Blastomeres The next division results in four blastomeres and takes place 40 hours after fertilization The third cleavage comprises the eight-cell stage and in At this stage, the blastomeres reach maximum contact with each other, forming a compact cellular sphere that is held together by est Right this process is Compaction Around the third day after fertilization, the cells of the compacted embryo divide again to form the 16-cell Morula. The cells inside the Morula constitute the internal cell mass and the cells that surround it constitute The outer cell mass The inner cell mass gives rise to the embryo and is therefore called the Embryoblast and the outer cell mass gives rise to the Trophoblast which in the future gives rise to the placenta On day 4, the morula enters the uterus and begins to penetrate fluid through the zona pellucida to the intercellular spaces of the inner cell mass this results in a space filled with fluid called Blastocele at this time the embryo is called Blastocyst and the embryoblast is positioned at a pole called Embryonic Pole and the cells of the trophoblast flatten and form the wall of the blastocyst.
