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Implantation quiz #1

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  • What are the main steps and cellular changes that occur during implantation of the blastocyst into the endometrium between days 6 and 12 post-conception?
    Implantation begins around days 6 to 9 post-conception when the blastocyst's trophoblast cells adhere to the receptive endometrium, which is prepared by increased estrogen and progesterone. The trophoblast differentiates into two layers: the cytotrophoblast and the syncytiotrophoblast. The syncytiotrophoblast erodes the endometrium by secreting digestive enzymes and growth factors, allowing nutrient absorption. By days 10 to 12, the embryoblast separates from the trophoblast, forming the bilaminar embryonic disc and the amniotic cavity. Endometrial cells proliferate to cover the blastocyst, completing implantation. The syncytiotrophoblast also begins secreting human chorionic gonadotropin (HCG), which is detectable in pregnancy tests.
  • What is implantation and when does it typically begin post-conception?
    Implantation is the embedding of a blastocyst into the endometrium and usually begins around day 6 post-conception.
  • Which hormones make the endometrium receptive to implantation?
    Estrogen and progesterone increase to make the endometrium receptive to implantation.
  • What are the two layers formed by the trophoblast during implantation?
    The trophoblast differentiates into the cytotrophoblast and the syncytiotrophoblast.
  • What is the main function of the syncytiotrophoblast during implantation?
    The syncytiotrophoblast erodes the endometrium by secreting digestive enzymes and growth factors, allowing nutrient absorption.
  • By which days does the embryoblast separate from the trophoblast, and what structures does it form?
    By days 10 to 12, the embryoblast separates from the trophoblast to form the bilaminar embryonic disc and the amniotic cavity.
  • What is the bilaminar embryonic disc and what does it go on to form?
    The bilaminar embryonic disc is a two-layered structure formed from the embryoblast, and it will develop into the embryo.
  • How is the blastocyst fully covered during the final stage of implantation?
    Endometrial cells proliferate and cover the blastocyst, completing the implantation process.
  • Which hormone does the syncytiotrophoblast begin to secrete around days 10 to 12, and why is it important?
    The syncytiotrophoblast begins secreting human chorionic gonadotropin (HCG), which is detectable in pregnancy tests.
  • Why is HCG detectable in pregnancy tests around the time a woman might miss her period?
    By about 12 days post-conception, HCG levels are high enough to be detected, which coincides with the time a woman would typically expect her period.