General Embryology 1 - Lecture 3
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Questions and Answers

What is the duration of the zygote period in humans?

  • 1 week
  • 4 weeks
  • 3 weeks
  • 2 weeks (correct)

    • Which stage follows the zygote period in human development?

  • Gastrulation
  • Embryo period (correct)
  • Cleavage
  • Fetus period

    • What does cleavage refer to in the context of embryonic development?

  • Formation of the zygote
  • Fusion of gametes
  • Division of the zygote into blastula (correct)
  • Development of germinal layers

    • What is the main function of organogenesis during the embryonic period?

    <p>Formation of different organs</p> Signup and view all the answers

    Which of the following refers to the differentiation of the embryonic cells into three germ layers?

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

    What are the male and female gametes specifically called during gametogenesis?

    <p>Sperms and ova</p> Signup and view all the answers

    What is the main characteristic of primordial germ cells (P.G.Cs.)?

    <p>They are responsible for gametogenesis.</p> Signup and view all the answers

    During which period does the increase in length and weight of the developing organs occur?

    <p>Fetus period</p> Signup and view all the answers

    What characterizes polyestrous animals in terms of their estrous cycle?

    <p>Their estrous cycle occurs repeatedly throughout the year at regular intervals.</p> Signup and view all the answers

    During which phase of the estrous cycle does ovulation occur?

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

    Which group of animals experiences estrous cycles only during certain seasons of the year?

    <p>Seasonal polyestrous animals</p> Signup and view all the answers

    What is the purpose of the diestrus phase in poly-estrous animals?

    <p>A rest period before the next proestrus cycle.</p> Signup and view all the answers

    What distinguishes monoestrous animals from other classifications?

    <p>They undergo one estrous cycle each breeding season.</p> Signup and view all the answers

    What is the initial stage of the process of spermatocytogenesis?

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

    What type of cells does spermatogonia differentiate into?

    <p>Primary spermatocytes</p> Signup and view all the answers

    Which process reduces the diploid number of chromosomes from 2N to 1N?

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

    At what stage do spermatids mature into mature sperm?

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

    What happens during the growth stage of spermatocytogenesis?

    <p>Spermatogonia type A increases in size</p> Signup and view all the answers

    During which period of spermatocytogenesis do mitotic divisions occur?

    <p>Multiplication phase</p> Signup and view all the answers

    Which cells are formed at the end of the first meiotic division?

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

    What is the term used for the formation of sperm cells?

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

    What is the term for the transformation of non-motile spermatids into motile spermatozoa?

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

    During spermiogenesis, what does the Golgi apparatus form?

    <p>Acrosomal cap</p> Signup and view all the answers

    Which stage of oogenesis occurs only during prenatal life?

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

    What is the end result of the second maturation division in oogenesis?

    <p>One ootid and three polar bodies</p> Signup and view all the answers

    What structure forms the middle piece of sperm during spermiogenesis?

    <p>Mitochondrial sheath</p> Signup and view all the answers

    Which of the following best describes a characteristic of the primary oocyte during the growth stage of oogenesis?

    <p>It remains dormant until puberty</p> Signup and view all the answers

    What occurs during the first meiotic division of a primary oocyte?

    <p>It produces one secondary oocyte and one polar body</p> Signup and view all the answers

    During spermatogenesis, where does the process primarily occur?

    <p>In the seminiferous tubules of the testis</p> Signup and view all the answers

    What causes the rupture of the stigma during ovulation?

    <p>Increased pressure in the follicular cavity</p> Signup and view all the answers

    What forms the corpus luteum after ovulation?

    <p>Granular layer and theca interna cells</p> Signup and view all the answers

    What is the fate of the corpus luteum if pregnancy does not occur?

    <p>It degenerates into corpus albicans</p> Signup and view all the answers

    Which hormone is crucial for the rupture of the follicle during ovulation?

    <p>Luteinizing Hormone (LH)</p> Signup and view all the answers

    What is described as the mass of cells surrounding the oocyte?

    <p>Cumulus Oophorus</p> Signup and view all the answers

    What type of ovulation occurs without being linked to coitus in most animals?

    <p>Spontaneous ovulation</p> Signup and view all the answers

    What is the initial structure formed immediately after the follicle ruptures?

    <p>Corpus haemorrhagicum</p> Signup and view all the answers

    Which part of the ovary does the mature follicle approach prior to ovulation?

    <p>Surface of the ovary</p> Signup and view all the answers

    What is the end result of spermiogenesis?

    <p>1 Ootid and 3 Polar Bodies</p> Signup and view all the answers

    What is the starting time for spermiogenesis?

    <p>From the time of puberty</p> Signup and view all the answers

    During which follicular stage do the follicular cells begin to secrete the Zona Pellucida?

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

    What characterizes the Graffian follicle?

    <p>The oocyte is eccentrically located and surrounded by the Cumulus Oophorus</p> Signup and view all the answers

    Which structure secretes estrogen during follicle development?

    <p>Theca interna</p> Signup and view all the answers

    Which statement is true about primordial follicles?

    <p>Each germ cell is surrounded by a single layer of flattened follicular cells</p> Signup and view all the answers

    When does the second meiotic division in spermatogenesis finish?

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

    What distinguishes the theca externa from the theca interna?

    <p>It does not contribute to hormone production</p> Signup and view all the answers

    Study Notes

    General Embryology 1 - Lecture 3

    • Developmental anatomy: The science of growth and differentiation of newly formed organisms, from single fertilized egg stage (zygote) to adulthood.
    • Embryology: Specific to the prenatal period in mammals (before birth) and pre-hatching period in birds.
    • Prenatal period: Stages in mammals
      • Zygote or fertilized ovum period: Begins at fertilization, lasting 2 weeks in humans, all cells are identical.
      • Embryo period: From end of the 2nd week to end of 8th week (or 6th week in some animals like horses and cattle) organs differentiate.
      • Fetus period: Fetus grows in size and weight, continuing until birth.

    Stages of Development

    • Gametogenesis: Formation of male and female gametes (sperm and ovum).
      • Haploid number of chromosomes (1N).
    • Fertilization: Fusion of male and female gametes to form a zygote that has a diploid number of chromosomes (2N).
    • Cleavage: Division of zygote into a mass of cells called a blastula.
    • Gastrulation: Arrangement of blastula cells into 3 germinal layers (ectoderm, mesoderm, and endoderm) to form a gastrula.
    • Organogenesis: Formation of organs. Occurs during the embryonic period.
    • Growth and histological differentiation: Increase in length and weight of developing organs, differentiation of tissues occurs during the fetal period.

    Spermatogenesis

    • Formation of sperms: Taking place within seminiferous tubules of the testes. Process occurs simultaneously from puberty to old age.
    • Spermatocytogenesis
      • Multiplication: Spermatogonia divide by mitosis into spermatogonia type A and type B. Spermatogonia type A grows, while type B divides into type A & type B after short rest period.
      • Growth: Spermatogonia type A increases in size to form primary spermatocyte (2n).
      • Maturation: Primary spermatocyte (2n) divides into 2 secondary spermatocytes (1n) through meiosis I. Each secondary spermatocyte divides into 2 spermatids (1n) through meiosis II.
    • Spermiogenesis: Non-motile spermatids transform into motile spermatozoa
      • Nucleus shrinks, forms head
      • Golgi forms acrosomal cap at anterior head end
      • Mitochondria form a sheath in the middle piece (energy source)
      • Centriole forms the axial filament (tail)
      • Cytoplasm removed
    • Stages: Spermatogonia, primary spermatocyte, secondary spermatocyte, spermatids, spermatozoa. All are haploid after meiosis II.

    Oogenesis

    • Formation of ova: Occurs in the cortex of the ovary.
    • Three stages :
      • Multiplication: Occurs only in prenatal life. Primary germ cells (oogonia) multiply by mitosis and form egg nests.
      • Growth: Oogonia develop into larger primary oocytes which rest until puberty.
      • Maturation: Primary oocyte divides by meiosis I into a secondary oocyte and a first polar body. The secondary oocyte divides by meiosis II to become an ootid (ovum), while the first polar body divides to give 2 polar bodies. Usually completed after fertilization.
      • Stages: Oogonium, primary oocyte, secondary oocyte, ootid/ovum.

    Ovarian Follicles

    • Developing ovum: Surrounded by a fibrocellular capsule (follicle)
      • Types of follicles: Primordial, primary, secondary, tertiary/Graffian
      • Features:
        • Primordial: Single layer of flattened follicular cells surrounding the germ cell (oocyte)
        • Primary: Oocyte enlarging in size, follicular cells becoming cuboidal
        • Secondary: Follicular cells divide, forming several layers and secreting a homogeneous material (Zona Pellucida).
        • Tertiary/Graffian: A large follicular cavity (antrum) appears, oocyte in eccentric position, surrounded by cumulus oophorus (granulosa cells). Theca interna and externa surrounding the follicle.

    Ovulation

    • Release of mature ovum from its follicle. Steps:
      • Mature follicle approaches ovary surface, becomes tense/blister-like. Clear avascular spot (stigma) is created.
      • Pressure of follicular fluid ruptures stigma, releases ovum with zona pellucida and corona radiata.
      • Infundibulum of uterine tube catches escaped ovum.
    • Types of ovulation: Spontaneous (not linked to coitus), Induced (occurs after coitus).

    Corpus Luteum

    • Formation: After ovulation, ruptured follicle cavity fills with blood clot (corpus haemorrhagicum). Cells from granulosa and theca interna multiply to create yellowish body (corpus luteum).
    • Function: Secretes progesterone (for pregnancy).
      • Degeneration: If no pregnancy, corpus luteum degenerates into corpus albicans. After parturition, corpus luteum degenerates into corpus albicans.

    Estrous Cycle

    • Definition: Cyclical reproductive process in animals (menstruation in humans).
    • Ovarian cycle: Growth, maturation of ovarian follicles, ovulation, corpus luteum formation.
    • Uterine cycle: Morphological changes in uterus to prepare for fertilized ovum.

    Classification of Animals by Estrous Cycle

    • Polyestrous: Repeated estrous cycle throughout the year (sow, cow).
    • Seasonal polyestrous: Repeated estrous cycle during specific seasons (cat, sheep, mare).
    • Seasonal monoestrous: One estrous cycle per season (bitch).
    • Monoestrous: One estrous cycle per year (deer, wild pig).

    Phases of Estrous Cycle

    • Proestrus: Follicles mature
    • Estrus: Ovulation, heat period
    • Metestrus: Corpus luteum forms
    • Diestrus: Period of rest preceding proestrus

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    General Embryology 1 Lecture 3 PDF

    Description

    Explore the intricate stages of developmental anatomy in mammal embryology, from fertilization to fetal growth. This quiz covers the processes including gametogenesis, cleavage, and the various developmental periods leading to adulthood. Test your knowledge of embryonic development and its stages.

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