Hi, I am looking for someone to write an article on development of the human placenta Paper must be at least 1250 words. Please, no plagiarized work! Implantation is the first step in the development of the placenta. Approximately 6th day after fertilization the blastocyst attaches to the endometrium and the process of implantation begins. Now the trophoblast layer of the blastocyst at the embryonic pole gets differentiated into two layers, an inner layer called cytotrophoblast and an outer layer called syncytiotrophoblast. The syncytiotrophoblast is highly invasive and expands quickly adjacent to the embryoblast, it produces enzymes that erode the maternal tissue enabling the blastocyst to burrow into the endometrium. The endometrial cells undergo apoptosis that facilitates invasion. The process of implantation is completed by the end of the second week and the blastocyst is superficially implanted in the endometrium.
At about day 10 blood-filled lacunae appear in the syncytiotrophoblast which ultimately fuses at day 12 to form the lacunar network, the primordia of intervillous spaces of the placenta, syncytiotrophoblast erodes the endometrial capillaries and maternal blood flows into these capillaries(sinusoids) giving rise to the primordial uteroplacental circulation. The rapidly proliferating cells of cytotrophoblast produce cellular extension that grows into the syncytiotrophoblast giving rise to the primary chorionic villi, mesenchyme soon grows into these primary villi giving rise to secondary villi. The mesenchymal cells soon differentiate into capillaries and blood cells, the villi at this stage are termed as tertiary villi they soon become connected with embryonic heart through vessels that differentiate in the mesenchyme. Cytotrophoblastic cells of the chorionic villi form a cytotrophoblastic shell that surrounds and attaches the chorionic sac to the endometrium. Villi that attach to the maternal tissues through the cytotrophoblastic shell are termed as stem villi from which the branch villi project.