PREGNANCY AND EMBRYONIC DEVELOPMENT

Cards (14)

  • Pregnancy - time from fertilization until infant is born
  • Conceptus - developing offspring
  • Embryo - period of time from fertilization until week 8
  • Fetus - week 9 until birth
  • Gestation period - from date of last period until birth (approx. 280 days)
  • For fertilization to occur, sexual intercourse must occur no more than 2 days before ovulation and no later than 24 hours after.
  • Zygote - first cell of a new individual
  • Cleavage - rapid series of mitotic divisions that begin with the zygote
  • Embryonic Development:
    • Zygote - first cell of a new individual; begins cleavage 24 hours after fertilization
    • Morula - a ball of 16 cells that forms 3 days after ovulation
    • Blastocyst - a ball of 100 cells; secretes human chorionic gonadotropin (hCG) to induce the corpus luteum to continue producing hormones; attaches to the endometrium 7 days after ovulation
  • Functional areas of the blastocyst:
    • Trophoblast - large fluid-filled sphere
    • Inner cell mass - cluster of cells to one side
  • Primary germ layers of the blastocyst:
    • Ectoderm - outside layer, gives rise to nervous system and epidermis
    • Mesoderm - middle layer, gives rise to everything else
    • Endoderm - inside layer, forms mucosae and associated glands
  • Amnion - fluid-filled sac that surrounds the embryo
  • Umbilical cord - blood vessel-containing stalk of tissue that attaches the fetus to the placenta
  • Placenta - forms a barrier between mother and embryo; delivers nutrients and oxygen