 Parental development in human the first trimester first the contents embryo, fetus and newborn trimesters the first trimester implantation of embryo gestulation and organogenesis and growth during first trimester so first the what is embryo? embryo, fetus and newborn as soon as the fertilization begins and the cell division starts it is called the embryo so right from fertilization till 8th week till 8th week the process in which the gestulation and embryonic layers are formed during this process we call it embryo after that once 9th week starts when 9th week starts development then it is said that young one is formed and young one begins to become the organ of it so when young one means the developing embryo starts to convert into a young one at this stage we call it fetus and after that after 9th week i.e. after becoming fetus till birth it is called fetus and after birth then we call it newborn baby young one three important phases of human development embryonic phase embryo phase fetus stage newborn young one stage if we discuss the total length of the human development then the total time span of human development i.e. 280 days 280 days is equal to 40 weeks so 40 weeks or 280 days is the total gestation period of the human till this much time the human stays in the uterus when there is development and growth now the total period is approximately 9 months so for 9 months scientists have divided this in 3 parts 1st 3 months middle 3 months and last 3 months when there are 3 months first trimester 2nd 3 months and last 3 months to study this So the first trimester, first trimester starts from the fertilization effect. As soon as the fertilization is done and the zygote is formed, the first trimester will start. And it will continue to be here until 3 months when it is completed. What is happening in the first trimester? After fertilization, as soon as the embryo or zygote is moving downward, it is moving downward in the flapping tube or in the oviduct towards the uterus. So the cell division is happening here. Until when it reaches the uterus, it is a blastoderm stage. When it reaches the blastoderm stage, it is called a blastoderm. As soon as it reaches the uterus, it is called a trophoblast. What will the trophoblast do? It will implant it along with the uterus wall. And this trophoblast is the cell that has to make a placenta in it. So it will be implanted. The trophoblast cell will impregnate. They will invade the uterus wall. They will invade the uterus wall and attach it to it. Now this is the unique stage. After this stage, along with it, the development process is completed. It is a blastoderm stage. It is a gastrulation stage. It is going on. So the work of implantation will be done during the blastoderm stage. In which the cell reaches approximately 120. Gastrulation stage. Now when the implantation is done, along with the gastrulation stage, it continues. During gastrulation, we all know that during gastrulation, there are embryonic layers. There are germ layers. During gastrulation, there will be an actoderm, endoderm, and the mesoderm formation. When the gastrulation process is done, the embryo will already be implanted. When it is attached to the uterus, the gastrulation stage is done. Gastrulation is the same as in birds or reptiles. In this stage, the epiblast cells migrate and come down. The primitive streak is formed. The cells migrate and come down. The endoderm and mesoderm will be formed. The ones above will be actoderms. Once the gastrulation is completed, when the gastrulation is formed, the endoderm and mesoderm will be formed. Now these germ layers will begin to form further organs. The actoderm will develop the nervous system and the skin. That is, the epiderm will develop. The development of the epiderm and the nervous system will be done by the actoderm. Usually, the cells we have from the endoderm are the gut cells. They are the cells of the digestive tract. Or a small portion of the respiratory tract. All the other body organs, bones, visceral organs, muscles, all these things are formed from the mesoderm. All these things are formed from the mesoderm. The process of organogenesis usually begins in the first trimester. Until the middle of the first trimester, the first trimester is 3 months, after a month and a half, all the embryos start to form the organs. After this stage, when all the organs start to form, we say it is the fittest now. From this stage, as soon as the first trimester is completed, all the body organs and organs have developed.