and embryonic development

and embryonic development The inner cell mass in the blastula is differentiated into epiblast and hypoblast immediately after implantation. The hypoblast is the embryonic endoderm and the epiblast This process is called implantation and it results in pregnancy. If the fertilized ovum is implanted outside the uterus it results in ectopic pregnancy . About percent of ectopic pregnancies occur in the fallopian tube. The growth of the embryo may cause internal bleeding, infection and in some cases even death due to rupture of the fallopian tube. D =\JRWH IHUWLOL]HGHJJ E FHOOVWDJH F 0RUXOD  G (DUO\EODVWRF\VW H LPSODQWHG EODVWRF\VW 2RF\WH  HJJ )HUWLOL]DWLRQ Fig. . From zygote to blastocyst : passage of growing embryo through the fallopian tube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ig. . Events of Fertilization XII Std Biology-Zoology Chapter- XII Std Biology-Zoology Chapter- Human Reproduction 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 uterine wall through the umbilical cord. It is the organ by which the nutritive, respiratory and excretory functions are fulfilled. The embryo’s heart develops during the fourth week of pregnancy and circulates blood through the umbilical cord and placenta as well as through its own tissues. The primary germ layers serve as the primitive tissues from which all body organs develop. The ectoderm gives rise to the central nervous system (brain and spinal cord), peripheral nervous system, epidermis and its derivatives and mammary glands. The connective tissue, cartilage and bone, muscles, organs of urinogenital system (kidney, ureter and gonads) arise from the mesoderm. The endodermal derivatives are e pithelium of gastrointestinal and respiratory tract, liver,