Fertilization and Cleavage Overview
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Questions and Answers

What is the primary consequence of insufficient mesoderm formation in the caudal region during gastrulation?

  • Development of congenital heart defects
  • Underdevelopment of the central nervous system
  • Growth of additional limbs
  • Formation of vertebral and urogenital abnormalities (correct)

    • What major developmental phase occurs from the third to the eighth week of embryogenesis?

  • Postnatal period
  • Fetal development
  • Pre-embryonic stage
  • Organogenesis (correct)

    • Which type of folding occurs due to the rapid longitudinal growth of the central nervous system during the embryonic period?

  • Transverse folding
  • Mediolateral folding
  • Lateral folding
  • Cephalocaudal folding (correct)

    • What is a potential consequence of teratogen exposure during the embryonic period?

    <p>Significant increase in birth defects</p> Signup and view all the answers

    What type of tumor can form from the pluripotent cells that persist in the sacrococcygeal region?

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

    What is the primary function of the acrosome in the spermatozoon?

    <p>Releasing enzymes necessary for fertilization</p> Signup and view all the answers

    Which part of the spermatozoon contains the mitochondria?

    <p>Middle piece</p> Signup and view all the answers

    Where does fertilization primarily occur within the female reproductive system?

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

    What is the purpose of capacitation in the fertilization process?

    <p>To prepare sperm for fertilization</p> Signup and view all the answers

    Which of the following statements is true regarding mitochondrial inheritance?

    <p>Mitochondria are inherited from the mother only</p> Signup and view all the answers

    During which stage does the spermatozoon undergo physiological changes to achieve fertilization capability?

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

    Which enzyme is NOT typically found in the acrosome of a spermatozoon?

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

    Which decidua is responsible for forming the maternal origin of the placenta?

    <p>Decidua basalis</p> Signup and view all the answers

    Which of the following correctly describes the decidua capsularis?

    <p>Covers the surface of the implanted blastocyst</p> Signup and view all the answers

    What happens to the decidua parietalis during the progression of pregnancy?

    <p>It fuses and degenerates</p> Signup and view all the answers

    What is primarily produced by the syncytiotrophoblast?

    <p>Human chorionic gonadotropin (hCG)</p> Signup and view all the answers

    Which type of ectopic pregnancy is most commonly found in the fallopian tube?

    <p>Extra uterine ectopic pregnancy</p> Signup and view all the answers

    What structure lies between the blastocyst and the uterine cavity?

    <p>Decidua capsularis</p> Signup and view all the answers

    What is the significance of detecting hCG levels by the end of the second week of pregnancy?

    <p>Confirms successful implantation</p> Signup and view all the answers

    What does the term 'placenta previa' refer to?

    <p>Placement of the placenta over the cervix</p> Signup and view all the answers

    What is the primary consequence of ectopic pregnancy?

    <p>Increased risk of maternal hemorrhage</p> Signup and view all the answers

    Which decidua lies at the junction between the capsularis and parietalis?

    <p>Decidua marginalis</p> Signup and view all the answers

    What is the extraembryonic mesoderm lining the cytotrophoblast and amnion called?

    <p>Extraembryonic somatopleuric mesoderm</p> Signup and view all the answers

    Which layers does the trophoblast differentiate into during the second week of development?

    <p>Syncytiotrophoblast and Cytotrophoblast</p> Signup and view all the answers

    What occurs during the second week of development that is considered a significant event?

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

    What are the two types of primary mesoderm that split during the second week?

    <p>Somatopleuric and Splanchnopleuric</p> Signup and view all the answers

    Which type of stem cells can differentiate into any other type of cells?

    <p>Totipotent stem cells</p> Signup and view all the answers

    Which of the following properties describes the ability of a stem cell to maintain its undifferentiated state through numerous cycles of division?

    <p>Self-renewal</p> Signup and view all the answers

    Which of the following is NOT a source of stem cells mentioned?

    <p>Induced pluripotent stem cells</p> Signup and view all the answers

    What is the significance of stem cells in medical treatments?

    <p>They can differentiate into damaged cells.</p> Signup and view all the answers

    What forms the bilaminar disc during the second week of development?

    <p>Layer of columnar epiblast and cuboidal hypoblast</p> Signup and view all the answers

    What is a characteristic of embryonic stem cells?

    <p>They are undifferentiated and can become any cell type.</p> Signup and view all the answers

    What is the role of the syncytiotrophoblast during the process of implantation?

    <p>To form finger-like processes that erode maternal tissues</p> Signup and view all the answers

    At what stage of development does the blastocyst typically implant into the endometrium?

    <p>Approximately 6 days after fertilization</p> Signup and view all the answers

    What transforms the endometrium into decidua post-implantation?

    <p>The interaction between trophoblast cells and endometrial tissues</p> Signup and view all the answers

    Which of the following processes occurs immediately after the disappearance of the zona pellucida?

    <p>The implantation of the blastocyst into the uterine lining</p> Signup and view all the answers

    What nourishes the blastocyst while it is floating freely in the uterus?

    <p>Secretions from the uterine glands</p> Signup and view all the answers

    What defines the normal site of implantation for the blastocyst?

    <p>The anterior or posterior wall of the uterine body</p> Signup and view all the answers

    What is the purpose of the enzymes produced by syncytiotrophoblast?

    <p>To erode maternal uterine tissues for implantation</p> Signup and view all the answers

    What indicates that the blastocyst is considered implanted?

    <p>It has penetrated the superficial layer of the endometrium</p> Signup and view all the answers

    What happens to the embryo during the two-cell stage of development?

    <p>It undergoes the first mitotic division</p> Signup and view all the answers

    What is the primary role of the middle piece in spermatozoa?

    <p>Provides energy for sperm motility</p> Signup and view all the answers

    What is the process called that sperm undergoes to gain the capability to fertilize an oocyte?

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

    Which statement correctly describes the composition of the spermatozoon nucleus?

    <p>It houses 22 autosomes and either the X or Y chromosome.</p> Signup and view all the answers

    What does the acrosome of the spermatozoon primarily contain?

    <p>Enzymes necessary for penetration of the oocyte</p> Signup and view all the answers

    Where does fertilization typically occur within the female reproductive system?

    <p>At the ampullary part of the uterine tube</p> Signup and view all the answers

    Which statement accurately reflects the characteristics of multipotent stem cells compared to embryonic stem cells?

    <p>Multipotent stem cells can only differentiate into a limited number of cell types.</p> Signup and view all the answers

    What is the primary function of the notochord during embryonic development?

    <p>It forms the central axis around which the axial skeleton develops.</p> Signup and view all the answers

    During gastrulation, what occurs at the primitive streak?

    <p>Cells migrate to form the definitive endoderm and intraembryonic mesoderm.</p> Signup and view all the answers

    What significant role does the notochord play in relation to the ectoderm?

    <p>It stimulates the overlying ectoderm to develop the central nervous system.</p> Signup and view all the answers

    What occurs to mesodermal cells during the invagination process during gastrulation?

    <p>They give rise to the definitive endoderm and contribute to mesoderm formation.</p> Signup and view all the answers

    What sequence correctly describes the phases of fertilization?

    <p>Penetration of the corona radiata, penetration of the zona pellucida, fusion of the oocyte and sperm head</p> Signup and view all the answers

    What is the primary result of fertilization occurring?

    <p>Restoration of the diploid number of chromosomes</p> Signup and view all the answers

    What process follows the morula stage during embryonic development?

    <p>Blastocyst formation</p> Signup and view all the answers

    During fertilization, which substances are primarily released during the acrosome reaction to facilitate penetration?

    <p>Acrosin and trypsin-like substances</p> Signup and view all the answers

    What nutrition source sustains the morula during its initial stages before reaching the uterus?

    <p>Cytoplasm of blastomeres</p> Signup and view all the answers

    What structure forms between the surface ectoderm and the neural tube as the neural folds fuse?

    <p>Neural crest</p> Signup and view all the answers

    During which critical period does the formation of most major organs and organ systems occur?

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

    Which type of villus develops as mesodermal cells penetrate the core of primary villi?

    <p>Secondary villus</p> Signup and view all the answers

    How does the fate of villi change as pregnancy progresses?

    <p>Villi on the embryonic pole grow and expand</p> Signup and view all the answers

    What is the primary feature of the chorion by the beginning of the third week?

    <p>Formation of primary villi</p> Signup and view all the answers

    Study Notes

    Fertilization, Cleavage, and Implantation

    • Fertilization is the fusion of mature sperm and ovum to form a zygote.
    • Fertilization typically occurs in the ampullary part of the uterine tube.
    • Spermatozoa require capacitation and acrosome reaction to fertilize the oocyte.
    • Spermatozoa consist of a head, neck, middle piece, principal piece, and end piece.
      • The head contains the nucleus and acrosome.
      • The middle piece contains mitochondria for motility.
    • The acrosome contains enzymes (e.g., acrosin) to penetrate the zona pellucida.
    • Fertilization steps:
      • Penetration of the corona radiata.
      • Penetration of the zona pellucida.
      • Fusion of oocyte and sperm head cell membranes.
    • Results of fertilization include:
      • Restoration of the diploid chromosome number.
      • Determination of the sex of the individual.
      • Initiation of cleavage.
    • After fertilization and cleavage, the embryo develops into a blastocyst.

    Cleavage

    • Cleavage is the mitotic division of the zygote.
    • Cleavage results in a rapid increase in the number of cells (blastomeres).
    • The embryo develops into a morula and then a blastocyst.
    • Blastocysts implant in the uterine lining (endometrium).

    Blastocyst

    • The blastocyst is formed from the morula.
    • The inner cell mass forms the embryo.
    • The trophoblast forms the fetal part of the placenta.
    • The blastocyst implants into the endometrial lining of the uterus.

    Implantation

    • Implantation is the embedding of the blastocyst into the uterine wall.
    • The trophoblast forms the cytotrophoblast and syncytiotrophoblast.
    • The syncytiotrophoblast erodes the uterine lining to allow the blastocyst to become implanted.
    • The endometrium is called the decidua after implantation.
      • Decidua basalis: part of the endometrium under the blastocyst (forms part of the placenta).
      • Decidua capsularis: the part of endometrium covering the implanted blastocyst
      • Decidua parietalis: the endometrium in the rest of the uterine cavity
    • Implantation occurs approximately 6-10 days after ovulation.

    The Second and Third Weeks of Development

    • The blastocyst is partially embedded in the endometrial stroma at the beginning of the second week.
    • The trophoblast differentiates into two layers: cytotrophoblast and syncytiotrophoblast.
    • Lacunae form in the syncytiotrophoblast, and maternal blood enters the lacunar network.
    • A primitive uteroplacental circulation begins by the end of the second week.
    • The inner cell mass forms the epiblast and hypoblast. These two form a bilaminar disk.
    • Extraembryonic mesoderm forms between the trophoblast and amnion.
    • The extraembryonic coelom or chorionic cavity forms.

    Gastrulation

    • Gastrulation is the process that transforms the bilaminar embryonic disk into a trilaminar embryonic disk.
    • The primitive streak forms on the epiblast.
    • Epiblast cells migrate through the primitive streak and differentiate into endoderm, mesoderm, and ectoderm.

    Neurulation

    • Neurulation is the process by which the neural tube forms.
    • The neural plate forms from the ectoderm.
    • The neural plate folds to form a neural tube.
    • The neural tube differentiates into the brain and spinal cord.

    Fetal Membranes

    • The fetal membranes include the chorion, amnion, yolk sac, and allantois.
    • The chorion, which is composed of the cytotrophoblast, syncytiotrophoblast, and extraembryonic mesoderm, forms the villi.
    • The villi penetrate the uterine lining, establishing a placental connection.
    • The amnion secretes amniotic fluid to surround and protect the developing embryo.
    • The yolk sac is involved in early nutrition and blood cell formation.
    • The allantois is important for the formation of the umbilical cord.

    The Placenta

    • The placenta develops from the chorion and decidua.
    • Its fetal side is called chorion frondosum and its maternal side decidua basalis.
    • The placenta connects the developing fetus to the mother.
    • Chorionic villi from the fetal side project into the intervillous space from the maternal side.
    • Through the placenta, nutrients and oxygen diffuse into the fetus, and fetal waste products diffuse out.

    Umbilical Cord

    • The umbilical cord consists of two umbilical arteries and one umbilical vein enclosed in Wharton's jelly.
    • It connects the fetus to the placenta.
    • It carries oxygen and nutrients from the placenta to the fetus and removes waste products from the fetus to the placenta.

    The Second and Third Trimester

    • The second and third trimesters are characterized by continued fetal growth, maturation of organs, and preparation for birth.
    • The fetus's head typically grows slower than the rest of the body.
    • The 3rd trimester is characterized by rapid fetal growth that includes deposition of subcutaneous fat.
    • Other developments include movement, skin development, and refinement of reflexes.

    Clinical Correlations

    • Low birth weight is associated with a range of complications, including neurological and developmental issues.
    • IUGR (Intrauterine Growth Restriction) is associated with various conditions, including genetic issues, maternal problems, and placental dysfunction.

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    Description

    This quiz explores the stages of fertilization, including the fusion of sperm and ovum to form a zygote. It also covers the process of cleavage, detailing the early stages of embryonic development and the significance of each phase. Test your knowledge on key terms and processes involved in human reproduction.

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