Formation of Germ Layers and Fertilization
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Questions and Answers

What is a result of fertilization in terms of chromosome number?

  • The zygote has a triploid chromosome number.
  • The diploid chromosome number is reduced to 23.
  • The germ layers are formed without any change in chromosome number.
  • The diploid chromosome number is restored to 46. (correct)

    • What determines the sex of the offspring at fertilization?

  • The type of spermatozoon that fertilizes the ovum. (correct)
  • The number of chromosomes in the spermatozoon.
  • The history of the parents' genetic traits.
  • The age of the parents at the time of fertilization.

    • How many chromosomes are present in a zygote if it is fertilized by a Y-bearing spermatozoon?

  • 46 + X + Y
  • 44 + Y
  • 44 + X + Y (correct)
  • 22 + Y chromosomes

    • During DNA replication, what structure is formed?

    <p>Two identical chromatids for each chromosome.</p> Signup and view all the answers

    Which statement about chromosome behavior during cell division is correct?

    <p>One chromosome from each pair moves to opposite ends of the spindle.</p> Signup and view all the answers

    What is the chromosomal composition of a girl offspring?

    <p>44 + X + X chromosomes.</p> Signup and view all the answers

    What is the origin of the chromosomes in each pair?

    <p>One chromosome derives from the mother and the other from the father.</p> Signup and view all the answers

    What process begins after fertilization in the ovum?

    <p>Cleavage.</p> Signup and view all the answers

    What is the term for the fertilized ovum when it consists of 16 cells?

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

    Which two germ layers are formed first in the embryonic disc?

    <p>Ectoderm and endoderm</p> Signup and view all the answers

    What structure forms the membrane called the chorion?

    <p>Somatopleuric mesoderm and trophoblast</p> Signup and view all the answers

    What separates the inner cell mass from the trophoblast in the morula stage?

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

    Which cavity appears first on the ectodermal side of the embryonic disc?

    <p>Amniotic cavity</p> Signup and view all the answers

    What is the name of the area in the embryonic disc that is not separated by mesoderm?

    <p>Prochordal plate</p> Signup and view all the answers

    What occurs to the morula as fluid increases from the uterine cavity?

    <p>It takes the shape of a cyst.</p> Signup and view all the answers

    What do the cells of the primitive streak contribute to in the embryonic development?

    <p>Development of the mesoderm</p> Signup and view all the answers

    At what stage is the embryo typically placed inside the uterus?

    <p>8-cell stage</p> Signup and view all the answers

    At what stage does the morula develop into a blastocyst?

    <p>After cleavage</p> Signup and view all the answers

    What are the two types of spermatozoa in terms of their chromosome composition?

    <p>22 + X and 22 + Y</p> Signup and view all the answers

    Which pole of the blastocyst is defined by the attachment of the inner cell mass?

    <p>Embryonic pole</p> Signup and view all the answers

    What is the cavity inside the blastocyst called?

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

    Which layer of cells becomes flattened as the morula develops into a blastocyst?

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

    What prevents the embryo from adhering to the uterine epithelium during its travel?

    <p>Zona pellucida</p> Signup and view all the answers

    What percentage of trials result in successful implantation of the embryo?

    <p>20%</p> Signup and view all the answers

    What is the term used to describe the process of the ovum dividing into smaller cells?

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

    What stage follows the '3-cell' stage in the cleavage process?

    <p>4-cell stage</p> Signup and view all the answers

    What is the structure that the morula resembles due to its appearance?

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

    What is the outer layer of cells surrounding the inner cell mass in the morula called?

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

    What is one of the primary hormones administered to women to stimulate follicle growth before ovulation?

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

    What is the name of the cluster of cells formed after 16 divisions of the ovum?

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

    In vitro fertilization involves which of the following processes?

    <p>Extraction of the ovum and fertilization outside the body</p> Signup and view all the answers

    What does the inner cell mass of the morula develop into?

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

    What is the role of growth factors in the context of stem cell culture?

    <p>They help maintain stem cells in an undifferentiated state.</p> Signup and view all the answers

    Which type of mesoderm is formed as a result of cells from the epiblast migrating during development?

    <p>Extra-embryonic mesoderm</p> Signup and view all the answers

    What is the advantage of using stem cells that are genetically identical to the patient?

    <p>Elimination of immune response against transplanted tissues.</p> Signup and view all the answers

    Which of the following cells can stem cells differentiate into?

    <p>Various types of adult cells, e.g., neurons and blood cells.</p> Signup and view all the answers

    Where can stem cells besides embryonic sources be isolated from?

    <p>Adult tissues such as bone marrow and brain.</p> Signup and view all the answers

    What is the main purpose of therapeutic stem cell cloning?

    <p>To produce genetically matched tissues for patients.</p> Signup and view all the answers

    What is the consequence of introducing a patient's cell nucleus into an embryonic stem cell?

    <p>It allows the stem cell to produce tissues compatible with the patient.</p> Signup and view all the answers

    How do embryonic stem cells maintain their undifferentiated state during in vitro culture?

    <p>Through exposure to specific growth factors.</p> Signup and view all the answers

    What is a significant drawback of using adult stem cells in research?

    <p>They are difficult to culture in laboratories.</p> Signup and view all the answers

    What ethical concern is raised regarding stem cell research involving human embryos?

    <p>It is seen as a violation of natural laws.</p> Signup and view all the answers

    What event marks the beginning of gastrulation in embryonic development?

    <p>Establishment of the primitive streak.</p> Signup and view all the answers

    At which stage of pregnancy is the embryo referred to as a morula?

    <p>At day 4.</p> Signup and view all the answers

    Which teratogenic influence during the pre-organogenesis period is likely to lead to the embryo's death?

    <p>Environmental toxins.</p> Signup and view all the answers

    During which week of pregnancy does the bilaminar disc form?

    <p>2nd week.</p> Signup and view all the answers

    What is the significance of the prochordal plate and primitive streak being seen at day 14?

    <p>Marks the onset of gastrulation.</p> Signup and view all the answers

    What are congenital anomalies most often attributed to during the embryonic period?

    <p>Teratogens.</p> Signup and view all the answers

    Study Notes

    Formation of Germ Layers

    • Fertilization occurs in the ampulla of the uterine tube
    • Fertilized ovum divides (cleavage)
    • 16 cells form morula
    • Morula develops into blastocyst with inner cell mass and trophoblast
    • Inner cell mass multiplies and forms an embryonic disc
    • Embryonic disc has ectoderm and endoderm
    • Mesoderm forms between ectoderm and endoderm
    • Amniotic cavity forms on ectodermal side
    • Yolk sac develops on endodermal side
    • Extra-embryonic mesoderm separates cavities from trophoblast
    • Extra-embryonic coelom splits extra-embryonic mesoderm into somatopleuric and splanchnopleuric layers
    • Chorion develops from trophoblast and somatopleuric mesoderm
    • Amnion forms from cells of amniotic cavity
    • Prochordal plate appears near one edge of embryonic disc
    • Primitive streak forms on embryonic disc
    • Primitive streak cells form mesoderm
    • Cloacal membrane forms caudal to primitive disc
    • This is made of ectoderm and endoderm

    Fertilization

    • Primary oocyte matures within ovarian follicle
    • Becomes secondary oocyte during ovulation
    • Secondary oocyte enters fallopian tube
    • Sperm fertilizes oocyte in ampulla
    • Sperm penetrates zona pellucida
    • Nuclei of ovum and sperm fuse (pronuclei)
    • 46 chromosomes restored
    • Sex determined by sperm type (X or Y)
    • Ovum divides into cells (cleavage)

    Cleavage

    • Two-celled stage forms
    • 3-celled stage, 4-celled stage, etc
    • Morula Forms
    • Blastocyst forms with blastocoele and inner cell mass
    • Blastocyst implants in uterine wall
    • Zona pellucida disappears
    • Trophoblast (outer cell layer) sticks to uterine wall
    • Additional nutrition available from uterine secretions and yolk

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    Formation of Germ Layers PDF

    Description

    This quiz covers the critical processes involved in the formation of germ layers during early embryonic development, including fertilization, cleavage, and the development of various structures such as the blastocyst and embryonic disc. Test your knowledge on the stages of embryogenesis and the interactions between different cellular layers.

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