Menstrual hygiene · Part 2

blastomeres . These produce cells, then and so on. After hours of Fertilization, a loose collection of cells forms a berry shaped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ig. . Events of Fertilization XII Std Zoology Chapter XII Std Zoology Chapter Human Reproduction to specific tissues, organs and organ systems during organogenesis. The extra embryonic membranes namely the amnion, yolk sac, allantois and chorion protect the embryo from dessication, mechanical shock and help in the absorption of nutrients and exchange of gases (Fig. . ) . The amnion is a double layered translucent membrane filled with the amniotic fluid. It provides a buoyant environment to protect the developing embryo from injury, regulates the temperature of the foetus and provides a medium in which the foetus can move. The yolk sac forms a part of the gut and is the source of the earliest blood cells and blood vessels. 3ODFHQWD 8PELOLFDO FRUG 8WHUXV &KRULRQ $PQLRQ $PQLRWLF IOXLG )RHWXV )DOORSLDQ WXEH $OODQWRLV 3ODFHQWDO YLOOL Fig. . Human foetus within the uterus The allantois forms a small out pocketing of embryonic tissue at the caudal end of the yolk sac. It is the structural base for the umbilical cord that links the embryo to the placenta and ultimately it becomes part of the urinary bladder. The chorion is the outermost membrane which encloses the embryo and all other membranes and also helps in the formation of the placenta. The trophoblast cells in the blastocyst send out several finger like projections called chorionic villi carrying foetal blood and are surrounded by sinuses that contain maternal blood. The chorionic villi and the uterine tissues form the disc-shaped placenta. Placenta is a temporary endocrine organ formed during pregnancy and it connects the foetus to the D =\JRWH IHUWLOL]HGHJJ