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Biology Essay Give an account of implantation and the functions of the placenta The zygote created from fertilization travels down and through the oviduct, dividing by nuclear and cell divisions by a process called cleavage, to form a tiny ball. The cells formed here are called blastomeres, which create a hollow ball of cells (the central cavity is called the blastocoel, which is filled with liquid from the oviduct). The outer layer of the blastomeres (trophoblast) thickens to form the 'inner cell mass'. When the body arrives at this stage (blastocyst), in the uterus, the zona pellucida starts to disappear allowing the trophoplast cells and the cells of the endometrium to make contact. In this process the trophoblast practically invades the walls, obtaining nutrients from the endometrium which allow the trophoblast cells to multiply. After a period of approximately six to nine days after fertilisation, the blastocyst becomes embedded inside the...

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