Fertilization and Early Embryo Development
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Questions and Answers

What is superfecundation?

  • Fertilization of a single ovum during different menstrual cycles
  • Fertilization of multiple ova by sperms from separate acts of coitus (correct)
  • Fertilization that occurs outside the uterine cavity
  • Fertilization of multiple ova by the same sperm during one act
  • What characterizes the morula stage?

  • Consists of 8 cells and enters the uterine cavity
  • Consists of 16 to 32 cells and is formed 3 days after fertilization (correct)
  • Is the last stage before implantation occurs
  • Contains a blastocoele filled with fluid
  • During which stage does the blastocyst begin to form?

  • 4 days after fertilization (correct)
  • At the morula stage
  • Immediately after fertilization
  • 2 days after fertilization
  • What is the function of the trophoblast in the blastocyst?

    <p>To create the placenta that nurtures the embryo</p> Signup and view all the answers

    What occurs during the cleavage or segmentation process?

    <p>The zygote experiences repeated mitosis, increasing the number of cells</p> Signup and view all the answers

    What is the site of fertilization in human reproduction?

    <p>Ampulla of uterine tube</p> Signup and view all the answers

    What is the purpose of capacitation in sperm?

    <p>To remove seminal plasma proteins from the sperm</p> Signup and view all the answers

    Which enzyme helps sperm penetrate the corona radiata during fertilization?

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

    What reaction occurs to prevent polyspermy after fertilization?

    <p>Zona cortical reaction</p> Signup and view all the answers

    What event follows the fusion of oocyte and sperm plasma membranes?

    <p>Second meiosis resumes in the oocyte</p> Signup and view all the answers

    What type of anomaly involves being pregnant without fertilization?

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

    What determines the sex of the embryo?

    <p>The chromosome carried by the sperm</p> Signup and view all the answers

    What is the chromosomal configuration of a zygote?

    <p>46S chromosomes</p> Signup and view all the answers

    Study Notes

    Fertilization

    • Definition: The union of male and female gametes
    • Location: Ampulla of the uterine tube
    • Steps:
      • Sperm deposited in the posterior fornix of the vagina (200-600 million)
      • Capacitation: Removal of proteins from sperm's head, making it more active. Happens in the female reproductive tract (5-7 hrs)
      • Acrosomal reaction: Enzymes released from the acrosome of the sperm to penetrate the corona radiata and zona pellucida.
      • Fusion of sperm and egg membranes
      • Zona cortical reaction: Prevents polyspermy (multiple sperm fertilizing an egg)
      • Second oocyte resumes meiosis, forming a female pronucleus
      • Male pronucleus formation (tail lost, nucleus enlarges)
      • Union of pronuclei: Formation of zygote (46 chromosomes)

    First Week Results

    • Sex determination: Y chromosome → male; X chromosome → female
    • Health assessment of the embryo
    • Resumption of meiosis II
    • Restoration of normal diploid chromosomes (46)
    • Initiation of zygote cell division

    Anomalies

    • Parthenogenesis: Embryo development without fertilization (all offspring female)
    • Dispermy (triploidy): Two sperm fertilize one ovum (zygote with 3 sets of chromosomes)
    • Superfecundation: Two ova are released and fertilized by sperm in the same menstrual cycle

    Cleavage (Segmentation)

    • Definition: Repeated mitosis of blastomeres (cells) to increase cell number within the fallopian tube
    • Steps:
      • 2-cell stage, 4-cell stage, 8-cell stage...etc.
      • Morula stage: (16-32) cells; formed 3 days after fertilization; enters uterine cavity
      • Blastocyst/Blastula stage: (4th day)
        • Blastocele: Fluid-filled cavity
        • Trophoblast: Outer layer of cells, forms part of placenta
        • Inner cell mass (embryoblast): Mass of cells that form the embryo

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    Description

    This quiz covers the complex process of fertilization, including the steps from gamete union to the formation of a zygote. It also addresses key developments during the first week after fertilization, such as sex determination and chromosome restoration. Test your understanding of these fundamental concepts in human reproduction.

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