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Questions and Answers
What type of implantation occurs in humans and apes?
What is the 'implantation window' in mice?
What happens to specific proteins during blastocyst activation?
Why is the degradation of ERα necessary?
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What is the 'refractory' phase in mice?
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What is the 'pre-receptive' phase in mice?
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What is the correct sequence of stages in embryonic implantation?
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How do mouse blastocysts implant during embryonic implantation?
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What type of implantation is characteristic of monkeys?
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What is the function of the primary syncytiotrophoblast in primate embryos during implantation?
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What type of cells are generated during implantation in mouse embryos?
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What is the difference between primate and rodent implantation regarding embryo orientation?
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What is the function of the trophectoderm adjacent to the inner cell mass in mouse embryos during implantation?
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What is the term for the process of embryonic implantation?
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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.
