{"id":103,"date":"2022-08-29T13:01:26","date_gmt":"2022-08-29T13:01:26","guid":{"rendered":"https:\/\/www.pregmed.org\/?page_id=103"},"modified":"2022-08-29T13:01:34","modified_gmt":"2022-08-29T13:01:34","slug":"4-weeks-pregnant","status":"publish","type":"page","link":"https:\/\/www.pregmed.org\/pregnancy-week-by-week\/4-weeks-pregnant","title":{"rendered":"4 Weeks Pregnant"},"content":{"rendered":"\n
After implantation, the blastocyst divides into different cell layers that form the placenta and the embryo (later to turn into the fetus). The embryo consists of two layers called the epiblast and hypoblast [1]<\/sup>. The epiblast layer divides into three essential cell layers \u2013 the ectoderm (it develops into the baby\u2019s nervous system, skin and hair), the endoderm (it develops into the gastrointestinal tract, pancreas, liver and thyroid) and the mesoderm (it develops into the connective tissue, skeleton, blood system, muscles and urogenital system) [2]<\/sup>. The hypoblast contributes to the formation of the yolk sac and extraembryonic mesoderm [3]<\/sup>.<\/p>\n\n\n