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Implantation bleeding occurs between 7 and 14 days after fertilization, [57] and is a small amount of light vaginal bleeding or spotting that can occur in early pregnancy due to the blastocyst penetrating the lining of the uterus during implantation.
Human embryology is the study of this development during the first eight weeks after fertilization. The normal period of gestation (pregnancy) is about nine months or 36 weeks. The germinal stage refers to the time from fertilization through the development of the early embryo until implantation is completed in the uterus.
Prior to implantation, the embryo remains in a protein shell, the zona pellucida, and undergoes a series of rapid mitotic cell divisions called cleavage. [3] A week after fertilization the embryo still has not grown in size, but hatches from the zona pellucida and adheres to the lining of the mother's uterus.
3. Morula. The ball of cells formed after the multiple divisions is called a morula. It consists of about 16-32 cells in a ball within a translucent, elastic layer called the zona pellucida. It will then undergo compaction which is a process where the cells bind firmly together and continue to develop into a blastocyst. [8] 4. Blastocyst
Thus, to develop such a complex and advanced brain in the end, the mammalian embryo needed to start this process earlier and to perform it faster. [ 3 ] Another difference is that during the development of embryonic genitourinary tract, in case of female embryo of placental and marsupial mammals, the uterus is formed, a structure that neither ...
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During these cellular divisions, the zygote remains the same size, but the number of cells increase. The morula enters the uterus after three or four days—during which a cavity, called the blastocoel, is formed to produce the blastocyst. [4] Once the blastocyst is formed, it undergoes implantation into the endometrium. [4]
How long you rest a steak depends on its size. “Smaller cuts like filet mignon should rest for 5 to 10 minutes , while larger cuts, like a tri tip, should rest for 10 to 20 minutes ," says Edwards.