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The germinal stage refers to the time from fertilization through the development of the early embryo until implantation is completed in the uterus. The germinal stage takes around 10 days. [1] During this stage, the zygote divides in a process called cleavage. A blastocyst is then formed and implants in the uterus.
Prenatal development starts with fertilization, in the germinal stage of embryonic development, and continues in fetal development until birth. In human pregnancy, prenatal development is also called antenatal development. The development of the human embryo follows fertilization, and continues as fetal development.
The germinal stage refers to the time from fertilization through the development of the early embryo until implantation is completed in the uterus. The germinal stage takes around 10 days. [2] During this stage, the zygote begins to divide, in a process called cleavage. A blastocyst is then formed and implanted in the uterus.
This phase is characterized by the activity of the corpus luteum, which produces progesterone. The signs of estrogen stimulation subside and the corpus luteum starts to form. The uterine lining begins to appear. In the absence of pregnancy, the diestrus phase (also termed pseudopregnancy) terminates with the regression of the corpus luteum. The ...
Organogenesis is the phase of embryonic development that starts at the end of gastrulation and continues until birth. During organogenesis, the three germ layers formed from gastrulation (the ectoderm, endoderm, and mesoderm) form the internal organs of the organism. [1] The endoderm of vertebrates produces tissue within the lungs, thyroid, and ...
Gastrulation is the next phase of embryonic development, and involves the development of two or more layers of cells (germinal layers). Animals that form two layers (such as Cnidaria) are called diploblastic, and those that form three (most other animals, from flatworms to humans) are called triploblastic.
Carnegie stage 2 (CS2) begins when the zygote undergoes its first cell division, and ends when the blastocyst forms a cavity and comprises more than 16 cells. At this point, it is called a morula . The cleavage divisions of CS2 embryos do not occur synchronously.
It ends at the end of week 27 (26 weeks + 6 days of GA) [37] or end of week 28 (27 weeks + 6 days of GA). [4] The third trimester is defined as starting, between the beginning of week 28 (27 weeks + 0 days of GA) [37] or beginning of week 29 (28 weeks + 0 days of GA). [4] It lasts until childbirth.