BI233 Lab Exercise 43

  1. The only place where gametes are produced
    • Testis
    • Ovary
  2. Haploid Complement
    • "n"
    • Half the number of chromosomes seen in all other body cells
    • = 23 in humans
  3. Gametogenesis
    • The process of gamete formation
    • Reduces chromosome number by half
  4. Purpose for halving chromosome number during gametogenesis
    The alternative would be that each subsequent generation would have double the chromosomes of the previous generation
  5. Homologous Chromosomes
    Egg/Sperm chromosomes that carry genes for the same traits
  6. Diploid
    • "2n"
    • 23 pairs of homologous chromosomes
    • 46 chromosomes
  7. Mitosis
    • Nuclear division process which reproduces cells
    • Creates a chromosome content exactly identical to all other cells in the body
  8. Meiosis
    • Specialized form of nuclear division producing the haploid number of chromosomes
    • Occurs in teh ovaeries and testes during gametogenesis
  9. Mother Cell
    • Initial cell of gametogenesis
    • Stem cell which undergoes chromosomal replication (as in mitosis) immediately prior to untergoing meiosis I and II
    • Produces 4 haploid daughter cells (rather than 2 diploid) from cytokinesis
  10. Synapsis
    • Event which occurs only in meiosis (not mitosis)
    • Pairing in which each homologous chromosome pair lines up closely along the length of the chromosome
    • Happens in prophase
  11. Tetrad
    • Image Upload 1
    • A grouping of four chromatids
    • 23 formed during synapsis
  12. Crossover
    • Image Upload 2
    • aka Chiasmata
    • During synapsis these are the points at which "arms" of adjacent chromosomes coil around each other
    • Point at which exchange may occur as homologues separate during Anaphase I
    • Event which provides innumberable genetic combinations
  13. Sister Chromatids
  14. Dyads
    Threads of chromatin held together by centromeresImage Upload 3
  15. Meiosis II
    Second maturation division of the cell in which chromosomes are NOT replicated
  16. Anaphase I separates the...
    Holologous chromosomes
  17. Anaphase II separates the...
    sister chromatids by breaking the centromeres
  18. List the sequence of events in Meiosis
    • Interphase
    • Prophase I
    • Metaphase I
    • Anaphase I
    • Telophase I
    • Cytokinesis
    • Prophase II
    • Metaphase II
    • Anaphase II
    • Telophase II
    • Cytokinesis
  19. Spermatogenesis
    Begins at puberty and proceeds continually throughout life
  20. Number of sperm in the average male ejaculation
    1/4 billion
  21. Site of spermatogenesis
    Seminiferous tubules (of the testes)
  22. Spermatogonia
    • Found at perifery of seminiferous tubules
    • Primitive stem cell from which sperm develop
    • Mitotic division before puberty produces 2 spermatogonium
    • Mitotic division after puberty produces 1 spermatogonium and on primary spermatocyte
  23. Hormone which induces spermatogonia to begin producing primary spermatocytes
    Follicle-stimulating hormone (FSH)
  24. Gland which secretes FSH
    Anterior Pituitary
  25. Primary Spermatocyte
    Cell which is created due to mitosis of spermatogonia (under influence of FSH) and proceeds to meiosis (as opposed to mitosis)
  26. Spermatids
    • Haploid cells that are the actual product of meiosis
    • Pre-gametes
    • Nonmotile cells which have too much excess baggage to function well in a reproductive capacity
  27. Spermiogenesis
    • Step which follows meiosis
    • Point at which excess cytoplasm is removed from teh spermatid and a streamlined sperm is created
    • Occurs in epididymus
  28. Image Upload 4
    • Seminiferous Tubules: from periphery --> lumen
    • Spermatogonia (pale-staining nuclei w/centrally located nucleoli)
    • Primary spermatocytes--undergoing nuclear division (contain coarse clumps of chromatin having coiled spring appearance)
    • Secondary spermatocytes (b/w Meiosis I and Meiosis II
    • (Sustentacular/Sertoli cells)
    • Spermatids (small w/round nucleus which may look lopsided due to loss of cytoplasm)
    • Immature sperm in lumen (have tails)
  29. Sertoli Cell
    • aka Sustentacular
    • Elongated cell in which spermatids are embedded
    • Extend inward from the periperhy of the tubule
    • Nourish the spermatids
  30. Interstitial Cells
    • aka Leydig cells
    • Lie external to (between) seminiferous tubules
  31. Luteinizing Hormone (LH)
    • aka Interstitial cell-stimulateing hormone
    • Triggers interstitial/Leydig cells to produce testosterone which acts synergistically w/FSH to stimulate sperm production
  32. Three regions of a mature sperm
    • Head (w/acrosome)--activating/genetic region
    • Midpiece--metabolic region
    • Tail--locomotor region
  33. Acrosome
    • Anterior to the nucleus in the head of the sperm
    • Contains enzymes used to penetrate egg
  34. Midpiece of sperm
    Centriole which gives rise to filaments which structure the sperm tail and is wrapped tightly w/mitochondria whcih provide ATP needed for contractile activity of the tail
  35. Tail of Sperm
    • Typical flagellum produced by a centriole
    • Powered by ATP to propel sperm
  36. What is the (female) cell type which starts the meiotic process
    Primary Oocyte
  37. Fertilization Membrane
    Relatively thick (appearing) cell membrane produced by the primary oocyte after sperm penetration
  38. What female structure(s) is produced during meiosis I
    • Secondary Oocyte
    • First Polar Body
  39. Follicle
    Sac-like structure within an ovary which immature ovum develop in
  40. Follicle Cells
    Cells which encase the ovum and form a single-cell layer saclike follicle
  41. Granulosa Cells
    Cells which encase the ovum and form a multi-cell layer saclike follicle
  42. These hormones are produced by the anterior pituitary and influence the development of ova (in ovaries) and cyclic production of female sex hormones by ovaries
    Gonadotropic Hormones
  43. Oogenesis
    Female gamete formation
  44. Oogonium
    primitive stem cell which eventually develops into oocyte
  45. Location of oogonia
    ovarian cortices of the developing female fetus
  46. Oogonia Mitosis
    Occurs thousands of times during female fetal development reaching a population of 2 million +
  47. Primordial Follicles (of the ovary)
    Single layer of squamouslike follicle cells which encapsulate each fetal oogonium
  48. Primary Oocyte
    • Cell form which occurs due to growth of oogonium
    • State of most gametogenic ovarian cells by the time of birth
    • Represent Prophase I
    • Cell form which is maintained until after puberty
  49. This hormone stimulates the advancement of the primary oocyte out of Prophase I
    Follicle Stimulating Hormone (FSH)
  50. Primary Follicle
    • Follicle resulting from the growth of the primordial follicle and a shift from squamous to cuboidal epithelium
    • Begins production of estrogens when stimulated by FSH
    • Stimulates the completion of Meiosis I when stimulated by FSH
    • [pic]
  51. Secondary Follicle
    • Follicle containing the primary oocyte (arrested in Prophase I) surrounded by granulosa cells
    • Contains multiple layers of granulosa ("follicle") cells as opposed to the single layer found in the primary follicle
    • Begins to show evidence of fluid accumulation and antrum formation
    • May take more than one cycle to develop
    • [pic]
  52. Secondary Oocyte
    • Result of the completion of meiosis I (along with first polar body)
    • Contains nearly all the cytoplasm from the primary oocyte
  53. First Polar Body
    • Along with the Secondary Oocyte it is the result of completion of meiosis I
    • Contains a minimum of the cytoplasm from the primary oocyte and will eventually disintegrate d/t lack of cytoplasm
    • May undergo meiosis II to produce two polar bodies which then disintegrate
  54. The follicle containing the secondary oocyte produces rising levels of estrogen to what effect
    • Initially it produces a negative feedback influence on the release of gonadotropins by the anterior pituitary
    • At midcycle (~ day 14 as the follicle reaches the vesicular/Graafian stage) the estrogen becomes highly stimulatory to the anterior pituitary which releases a burst of LH (and some FSH) to trigger ovulation
  55. When does the estrogen released by the oocyte's follicle move from inhibiting the anterior pituitary to stimulating it?
    About midcycle as the follicle moves from primary to vesicular/Graafian stage
  56. What is released by the anterior pituitary to stimulate ovulation of the secondary oocyte (metaphase II stage)?
    A burst of LH as well as FSH
  57. Vesicular/Graafian follicle
  58. What is required for the ovum to complete meiosis II
    It must be penetrated/fertilized by sperm in order to continue past metaphase II
  59. Where is the ovum fertilized
    In the first third of the uterine tube
  60. What happens in the ovum once the second maturation dividsion is complete?
    The chromosomes of the egg and sperm combine to form the diploid nucleus of the fertilized egg
  61. What is the end product of meiosis in the female?
    A single functional gamete and 3 polar bodies
  62. Corpus Luteum
    • Ruptured follicle which has been transformed by LH after expelling an oocyte
    • Solid glandular structure or scalloped lumen structure
    • Structure which produces progesterone and estrogen thus inhibiting FSH production in the anterior pituitary
    • [pic]
  63. Impact of progesterone/estrogen on the anterior pituitary
    Inhibits FSH release
  64. Effect of decreasing levels of FSH
    • Decreasing stimulatory effect on folliclular producion of estrogenImage Upload 5
    • Decreased stimulation of anterior pituitary to release LHImage Upload 6
    • Decreased stimulation of corpus luteumImage Upload 7
    • Declining progesterone production by corpus luteumImage Upload 8
    • Eventual degeneration of corpus luteum in to scar tissue--corpus albicans
  65. Corpus Albicans
    • [pic]
    • scar tissue which forms near the end of the 28-day cycle as a result of the degeneration of the corpus luteum
  66. Germinal Epithelium
    [pic] outermost layer of the ovary
  67. Antrum
    • Central cavity of an ovarian follicle which begins to form in the secondary follicle and becomes prominent in the vesicular/Graafian stage
    • [pic]
  68. Vesicular/Graafian Follicle
    • Follicle containing a developing secondary oocyte which is pushed to the side by a large antrum filled with fluid from the granulosa cells
    • [pic]
  69. Corona Radiata
    • Several layers of granulosa cells which surround the secondary oocyte within the antrum of the vesicular/Graafian follicle
    • Structure which is retained as oocyte is ovulated
  70. Theca Folliculi
    • Connective tissue stroma which forms a capsule enclosing the mature vesicular/Graafian follicle
    • [pic]
  71. Uterine/Menstrual Cycle
    • Cycle controlled by hormones (estrogen/progesterone) secreted by the ovary
    • Divided into 3 stages--menstrual, proliferative, secretory
  72. What are the three stages of the menstrual/uterine cycle?
    • Menstrual
    • Proliferative
    • Secretory
  73. What happens during the menstrual stage of the uterine cycle?
    Shedding of the functional layer of endometrium (days 1-5 )
  74. What happens during the proliferative stage of the uterine cycle?
    Estrogens influence the rebuilding of the (endometrial) functional layer (days 6-14)
  75. What happens during the secretory stage of the uterine cycle?
    Immediately after ovulation progesterone triggers the endometrium to receive an embryo by enriching the blood supply and increasing glandular secretion of nutrients (days 15-28)
  76. Impact of embryo on corpus luteum
    Production of a hormone similar to LH will maintain the function of the corpus luteum preventing deterioration and inhibiting the secretion of ovarian hormones.  As a result the endometrial blood vessels continue to proliferate
Card Set
BI233 Lab Exercise 43
Physiology of Reproduction: Gametogenesis and the Female Cycles