Embryology Lecture 2: Implantation
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Questions and Answers

What type of implantation occurs in humans and apes?

  • Intramural implantation
  • Central implantation
  • Interstitial implantation (correct)
  • Superficial implantation

    • What is the 'implantation window' in mice?

  • The time when the mother is receptive
  • The entire gestation period
  • The time when the embryo is developed
  • A specific period of time when implantation is possible (correct)

    • What happens to specific proteins during blastocyst activation?

  • They remain unchanged
  • Some are upregulated and others are downregulated (correct)
  • They are all downregulated
  • They are all upregulated

    • Why is the degradation of ERα necessary?

    <p>For the implantation of the blastocyst</p> Signup and view all the answers

    What is the 'refractory' phase in mice?

    <p>The phase when the uterus is not receptive</p> Signup and view all the answers

    What is the 'pre-receptive' phase in mice?

    <p>The phase before the uterus is receptive</p> Signup and view all the answers

    What is the correct sequence of stages in embryonic implantation?

    <p>Embryo spacing, Apposition, Orientation, Attachment, Invasion</p> Signup and view all the answers

    How do mouse blastocysts implant during embryonic implantation?

    <p>With the mural side of the embryo</p> Signup and view all the answers

    What type of implantation is characteristic of monkeys?

    <p>Superficial implantation</p> Signup and view all the answers

    What is the function of the primary syncytiotrophoblast in primate embryos during implantation?

    <p>To facilitate histotrophic nutrition of the embryo</p> Signup and view all the answers

    What type of cells are generated during implantation in mouse embryos?

    <p>Invasive multinucleated trophoblast giant cells</p> Signup and view all the answers

    What is the difference between primate and rodent implantation regarding embryo orientation?

    <p>Primates attach with the polar side, while rodents attach with the mural side</p> Signup and view all the answers

    What is the function of the trophectoderm adjacent to the inner cell mass in mouse embryos during implantation?

    <p>To form extraembryonic ectoderm</p> Signup and view all the answers

    What is the term for the process of embryonic implantation?

    <p>Implantation</p> Signup and view all the answers

    Study Notes

    Implantation

    • Implantation is a complex process that involves at least five stages: embryo spacing, apposition, orientation, attachment, and invasion.
    • Primate implantation differs from rodents in terms of embryo orientation, cell types mediating implantation, and lineage potential of early trophoblast cells.

    Implantation in Mouse

    • Mouse blastocysts implant with the mural side of the embryo (trophectoderm compartment away from the inner cell mass) and generate invasive multinucleated trophoblast giant cells.
    • The polar side of the embryo remains proliferative and forms extraembryonic ectoderm that expands and differentiates into the labyrinthine structure of the mouse placenta.

    Implantation in Primates

    • Primate embryos first attach with the polar side, wherein polar trophectoderm differentiates into multinucleated primary syncytiotrophoblast and proliferative cytotrophoblast.
    • The invasive primary syncytiotrophoblast penetrates the basal lamina of the luminal epithelium and is essential for the formation of fluid-filled lacunae to facilitate histotrophic nutrition of the embryo.

    Types of Implantation

    • Eccentric implantation (mouse, rat): The embryo partially embeds into the uterine tissues, leaving portions of the conceptus exposed to the uterine cavity.
    • Superficial implantation (monkeys): The embryo remains within the uterine cavity and is often associated with shallow trophoblast invasion.
    • Interstitial implantation (apes, human): The embryo penetrates deep into the uterus and becomes fully engulfed in the endometrial tissue.

    Implantation Window Concept

    • In mice, there are three phases of uterine sensitivity for receiving the embryo: pre-receptive phase (days 1-3), receptive phase (days 4-5), and refractory phase (beyond the afternoon of day 5).
    • The receptive phase is the only time when embryos can implant into the uterine epithelium, and this specific period is called the "implantation window".

    Blastocyst Implantation Competency

    • The downregulation of specific proteins (such as ERα) in the activated blastocyst is critical for successful implantation.
    • Expressed proteins in activated blastocysts are categorized into three groups: essential, expressed but unnecessary, and obligatorily downregulated to complete blastocyst implantation.

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    Description

    Learn about the process of embryonic implantation, its stages, and the differences between primate and rodent implantation.

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