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Introduction to Human Development definitions

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  • Conception
    The moment an oocyte is fertilized by a sperm cell, marking the start of development.
  • Conceptus
    A term for the developing offspring, applicable to both embryos and fetuses.
  • Gestational period
    The time from the mother's last menstrual period to birth, typically 40 weeks.
  • Preembryonic stage
    The first two weeks post-conception, where the conceptus is called a blastocyst.
  • Embryonic period
    Weeks 3-8 post-conception, characterized by rapid development and organ formation.
  • Fetal stage
    Weeks 9-38 post-conception, where the conceptus is referred to as a fetus.
  • Blastocyst
    A structure formed in the early development stage, consisting of a cell mass.
  • Trilaminar disc
    A three-layered structure formed during the embryonic period.
  • Fertilization
    The process where a sperm cell merges with an oocyte, initiating development.
  • Cleavage
    A series of rapid cell divisions following fertilization, leading to blastocyst formation.
  • Implantation
    The process of the blastocyst embedding into the uterine wall.
  • Gastrulation
    The formation of the trilaminar disc from the blastocyst.
  • Organogenesis
    The formation and development of organs during the embryonic period.
  • Placentation
    The development and growth of the placenta, beginning early in embryonic development.
  • Extraembryonic membranes
    Membranes that develop outside the embryo, starting in the preembryonic stage.