Biology Chapter on Gametogenesis
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Questions and Answers

What is the correct sequence of development in spermatogenesis?

  • Spermatogonia ➔ primary spermatocyte ➔ secondary spermatocyte ➔ spermatids (correct)
  • Spermatogonia ➔ secondary spermatocyte ➔ spermatids ➔ mature sperm
  • Primary oocyte ➔ oogonia ➔ secondary oocyte ➔ mature egg
  • Oogonia ➔ primary oocyte ➔ secondary oocyte ➔ mature oocyte
  • Which structure provides the motility for sperm?

  • Acrosome
  • Head
  • Neck
  • Tail (correct)
  • What happens during spermiogenesis?

  • Formation of primary oocytes from oogonia
  • Maturation of spermatids into mature sperm (correct)
  • Transformation from spermatogonia to spermatids
  • Division of primary spermatocytes
  • What initiates the process of oogenesis?

    <p>Proliferation of oogonia during early fetal life</p> Signup and view all the answers

    What surrounds the primary oocyte and forms a primordial follicle?

    <p>Follicular epithelial cells</p> Signup and view all the answers

    Which of the following is NOT a part of the structure of a sperm?

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

    During which phase does the transformation of primary oocytes to mature oocytes finish?

    <p>At menopause</p> Signup and view all the answers

    What is the role of Sertoli cells in the seminiferous tubules?

    <p>Support and nourish germ cells</p> Signup and view all the answers

    What distinguishes a diploid cell from a haploid cell?

    <p>A diploid cell has 46 chromosomes arranged in 23 pairs.</p> Signup and view all the answers

    Which of the following statements about gametogenesis is true?

    <p>Both spermatogenesis and oogenesis involve differentiation of primordial germ cells.</p> Signup and view all the answers

    What is the primary purpose of meiosis in gametogenesis?

    <p>To reduce the chromosome number in gametes to ensure genetic diversity.</p> Signup and view all the answers

    What is the earliest stage of gamete development in humans?

    <p>Germ cell</p> Signup and view all the answers

    Which of the following correctly describes oogenesis?

    <p>It produces secondary oocytes that can undergo meiosis only upon fertilization.</p> Signup and view all the answers

    What defines the sex chromosomes in humans?

    <p>They determine whether an individual is female (XX) or male (XY).</p> Signup and view all the answers

    Which phase of gametogenesis does not involve a reduction in chromosome number?

    <p>Mitosis of germ cells</p> Signup and view all the answers

    During which stage do primordial germ cells begin their migration to the gonadal ridge?

    <p>During early embryonic development.</p> Signup and view all the answers

    What is the primary function of the testes in the male reproductive system?

    <p>To produce sperm and testosterone</p> Signup and view all the answers

    Which structure is responsible for the maturation and storage of sperm?

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

    What percentage of seminal fluid is secreted by the seminal vesicles?

    <p>60%</p> Signup and view all the answers

    Which of the following statements about Sertoli cells is true?

    <p>They provide physical support and nutrition to spermatocytes.</p> Signup and view all the answers

    Which ducts carry sperm from the seminiferous tubules to the duct of the epididymis?

    <p>Efferent ductules</p> Signup and view all the answers

    What is the role of the prostate gland in the male reproductive system?

    <p>Production of seminal fluid containing citrate and fibrinolysin</p> Signup and view all the answers

    Which anatomical term refers to the body position where the upper limbs are by the sides and the palms face forward?

    <p>Anatomical position</p> Signup and view all the answers

    The interstitial cells found in the testes are primarily responsible for producing which hormone?

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

    What do seminiferous tubules primarily produce?

    <p>Sperm cells</p> Signup and view all the answers

    What is the main contribution of Cowper's glands in the male reproductive system?

    <p>Secretion of lubricating fluid</p> Signup and view all the answers

    Study Notes

    General Human Embryology

    • This study covers general human embryology.
    • It is the field of embryology concerning changes in cells, tissues, and organs, and the overall body, from parent germ cells to the resulting adult.
    • Embryology studies embryos, focusing on prenatal development.
    • Teratology is a division of embryology and pathology, dealing with abnormal development (birth defects).

    Embryologic Terminology

    • Oocyte (ovum, egg): female germ cells produced in the ovaries.
    • Sperm (sperma, seed): male germ cells produced in the testes.
    • Zygote: the result of uniting an oocyte and sperm during fertilization; the beginning of a new human life.
    • Cleavage: a series of mitotic divisions of the zygote, leading to early embryonic cells (blastomeres).
    • Morula: a solid mass of 12-32 blastomeres around 3-4 days post-fertilization, entering the uterus.
    • Blastocyst: the structure formed when the morula develops a fluid-filled cavity.
    • Implantation: the process where the blastocyst attaches to the endometrium (around 6 days post-fertilization).
    • Gastrula: the stage of development during the third week where the three germ layers emerge.
    • Neurula: the stage of development (3rd-4th week) characterized by a developing neural tube from the neural plate.
    • Embryo: early stages of human development, ending at the eighth week (56 days).
    • Fetus: the unborn offspring after the embryonic stage until birth.
    • Conceptus: the embryo and its associated membranes, such as the placenta.

    Descriptive Terms in Embryology

    • Anatomical position is assumed for descriptions: erect body, upper limbs at the sides, palms forward.
    • Several terms describe relationships and planes:
      • Anterior/posterior
      • Dorsal/ventral
      • Superior/inferior
      • Cranial/rostral/caudal
      • Proximal/distal
      • Median plane
      • Sagittal plane
      • Coronal plane

    Male Reproductive System

    • Components:
      • Primary sex organs (testes)
      • System of ducts (e.g., epididymis, ductus deferens, urethra)
      • Accessory sex glands (e.g., seminal vesicles, prostate, bulbourethral glands)

    Male Reproductive Structures

    • Testis: the male sex gland, lying in the scrotum, enclosed by the tunica vaginalis; divided into 250 lobules, containing seminiferous tubules responsible for sperm production, and interstitial cells that create testosterone.

    Intratesticular Genital Ducts

    • Straight tubules (tubuli recti)
    • Rete testis
    • Efferent ductules

    Epididymis

    • A much-coiled tube where sperm mature and are stored.
    • It adds glycoprotein coat and seminal proteins around the sperm.

    Ductus/Vas Deferens

    • A thick muscular tube carrying mature sperm from the epididymis to the ejaculatory duct.

    Ejaculatory Duct

    • The union of the ampulla of the ductus deferens with the ducts of the seminal vesicle.
    • Sperm enters the prostate gland and prostatic urethra from here.

    Male Accessory Sex Glands

    • Seminal vesicles, Prostate, and Cowper's glands secrete fluids that comprise the bulk of semen.

    The Accessory Glands (Male)

    • Seminal vesicle: Secretes 60% of seminal fluid, containing fructose for nutrition, prostaglandins, and enzymes.
    • Prostate gland: Secretes 30% of seminal fluid containing citrate, fibrinolysin.
    • Cowper's gland: Secretes an alkaline fluid that neutralizes acidity of the urethra.

    Female Reproductive Structures

    • Primary sex organs (ovaries)
    • Fallopian tubes
    • Uterus
    • Vagina
    • External genitalia

    Uterus

    • A hollow muscular organ, where a fertilized ovum grows and is nourished until birth.
    • Its components include the fundus (top part), body, isthmus, and cervix.
    • The cavity of the uterus and vagina forms the birth canal.
    • The uterus has an inverted pear shape
    • The wall of the body of the uterus consists of three layers: perimetrium, myometrium, and endometrium.

    Uterine/Fallopian Tubes

    • These tubes transport oocytes from the ovaries to the uterus, and spermatozoa in the opposite direction.
    • Fertilization occurs within the uterine tubes.
    • Length ~10-12cm
    • The tubes are lined with secretory epithelium for nourishment.
    • The infundibulum is the funnel-shaped part near the ovaries with fimbriae (finger-like projections).
    • The ampulla is the widest part, followed by the isthmus and intramural (uterine) part.

    Ovaries

    • The female sex gland, located in the ovarian fossa of the pelvis.
    • Function: production of ova.
    • Secretes estrogen and progesterone.

    Ovarian Cycle

    • The monthly series of events associated with the maturation of an ovum.
    • Consists of two phases:
      • Follicular Phase (days 1-14): follicle growth
      • Luteal Phase (days 14-28): corpus luteum activity.

    Ovulation

    • The release of a mature secondary oocyte.
    • Usually occurs mid-cycle.
    • Ovarian follicle swells into a cyst, then ruptures, releasing the oocyte.
    • This cyclical process involves hormones produced by the hypothalamus, pituitary gland, and ovary.

    The Corpus Luteum

    • A temporary endocrine gland formed from the ruptured follicle after ovulation.
    • Essential for pregnancy maintenance.
      • Degenerates if pregnancy does not occur (corpus luteum of menstruation).
      • Remains if pregnancy occurs (corpus luteum of pregnancy).

    The Uterine (Menstrual) Cycle

    • The monthly cyclical changes to the endometrium.
    • Corresponds to the phases of the ovarian cycle.
    • Stages:
      • Menstrual phase: sloughing of the endometrium
      • Proliferative/follicular phase: rebuilding of the endometrium
      • Secretory/luteal phase: preparation for implantation

    Anovulatory Menstruation & Artificial Induction of Ovulation

    • Some women do not ovulate due to low gonadotropin levels, and require artificial stimulation.
    • Although such treatments are effective, the chance of multiple births increase significantly.

    The Beginning of Human Development

    Gametogenesis

    • The production of gametes (ova and spermatozoa)
    • Consists of several phases, including extragonadal origin of primordial germ cells, proliferation of germ cells, meiosis, and maturation of gametes.

    Chromosomes

    • Human somatic cells (body cells) have 46 chromosomes (23 pairs).
    • 22 pairs of autosomes and 1 pair of sex chromosomes.
    • Diploid cells contain 23 pairs of chromosomes.
    • Homologous and pair chromosomes determine sex (XX for female, XY for male).

    Meiosis

    • A specialized cell division involving two meiotic divisions ( I & II).
    • Important for producing haploid gametes from diploid germ cells.
    • Meiosis I involves homologous chromosome pairing and separation. Meiosis II involves sister chromatid separation.

    Polar Bodies

    • Cells that result from unequal cytoplasmic division during oogenesis.

    Chromosomal Abnormalities

    • Numerical or structural
    • Numerical: Euploid (exact multiples of n) and Aneuploid (extra or missing chromosome)
    • Structural: Translocation, inversion, deletion(loss of part of a chromosome)
    • Examples: Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), Cri du chat syndrome.

    Spermatogenesis

    • A sequence where spermatogonia are transformed into mature sperm.
    • Occurs in the seminiferous tubules.
    • Includes mitosis, meiosis, and spermiogenesis.
    • Sertoli cells support and nourish the germ cells during spermatogenesis.

    Oogenesis (Ovogenesis)

    • Sequence of events by which oogonia form mature oocytes.
    • Begins before birth; maturation continues into puberty and is not done until menopause.

    Capacitation & Dispermy

    • Sperm conditioning period in the female reproductive tract
    • Essential for fertilization
    • Dispermy: fertilization of egg by two sperm - results in a zygote with an extra set of chromosomes.

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    Test your knowledge on the processes of spermatogenesis and oogenesis with this quiz. Explore key concepts such as the stages of gamete development, the roles of various cells, and the differences between diploid and haploid cells. Perfect for students studying developmental biology or reproductive systems.

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