Chapter 5: Sex Determination & Fetal Sexual Differentiation

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  1. Humans have _____ chromosomes, or _____ pairs?
    46 chromosomes; 23 pairs
  2. Pairs 1-22 are called _____.
  3. The 23rd pair is the _____ _____.
    Sex Chromosomes
  4. The _____ determines the genetic sex of the child.
  5. The _____ _____ is contained in the Y Chromosome, and is the strongest determinant of sexual differentiation.
    SRY Gene
  6. The first 7 weeks are the _____ _____ period, in which the SRY gene has not made the determination between ovaries and testes.
    Indifferent Gonad
  7. The presence of 2 X Chromosomes (XX) or 1X and 1Y Determined at fertilization.
    Stage 1 (Chromosomal Sex)
  8. All eggs contain __________.
    22 autosomes & 1X
  9. All sperm contain _____.
    22 autosomes & either 1X or 1Y Chromosome.
  10. The presence of either ovaries or testes; determined by chromosomal sex.
    Stage 2: Gonadal Sex
  11. XX individuals form _____.
  12. XY individuals form _____.
  13. The conversion of the indifferent gonad into a testis or ovary.
    Sex Determination
  14. Begins development in late 3 wee old embryo and develops from two tissues.
    The Indifferent Gonad (3-6 week)
  15. 2 masses of somatic cells (supporting & steroidogenic) that form medial to the embryonic kidneys (mesonephros).
    Genital Ridges
  16. Contained in the yolk sac of the embryo. Will migrate around the 6th week into the genital ridge. Develop into germ cells (oogonia or spermatogonia).
    Primordial Germ Cells (PGC's)
  17. Begins during the 7th week in XY embryo and is initiated by SRY gene on the Y Chromosome.
    Formation of the Testis
  18. Steroidogenic cells form the ______ cells.
  19. Leydig cells secrete ______.
  20. Supporting cells form the ______ cells.
  21. Sertoli cells secrete ______.
  22. Why are they called supporting cells?
    Because they typically do not secrete hormones.
  23. ______ is very important for determining male internal genitalia.
  24. ______ form the spermatogonia 2n.
  25. ______ are arrested until puberty.
    Spermatogonia 2n
  26. Begins during the 10th-12th week in XX embryo.
    Formation of the ovary
  27. Formation of the ovary is initiated by ______.
    Absence of the SRY gene.
  28. In the formation of the ovary, the ______ gene is required to act on X.
  29. Suppresses DMRT1, DMRT2 & SOX9 genes during formation of the ovary.
    DAX1 gene on X.
  30. During formation of the ovary, steroidogenic cells will form ______ cells.
  31. Theca cells synthesize ______.
  32. In formation of the ovary, supporting cells form ______, or ______ cells.
    Follicle, or Granulosa
  33. Follicle (Granulosa) cells convert ______ to ______.
    Androgens to Estrogen
  34. PGC's form ______.
  35. Development of the internal & external genitalia.
    Sexual Differentiation (Phenotypic)
  36. ______ ______ develop from paramesonephric ducts, mesonephric ducts & urogenital sinus.
    Internal Genitalia
  37. Mullerian ducts are ______.
  38. Wolffian ducts are _____.
  39. Paramesonephric ducts are also known as ______ ducts.
  40. Mesonephric ducts are also known as ______ ducts.
  41. The XY (male) embryo develops ______ ______ during the 8th-11th weeks.
    Internal Genitalia
  42. In the paramesonephric (Mullerian) ducts, ______ is needed to degenerate the female hormone in order for the embryo to become a male.
  43. The mesonephric (Wolffian) duct is stimulated by ______ to form the ______, ______ & ______.
    testosterone; epididymis, vas deferens & seminal vesicles.
  44. ______ ______ is gained in the epididymis and remain there until ready to be utilized.
    Sperm motility
  45. The ______ ______ is the transport for the sperm to the glands to form semen.
    Vas deferens
  46. The ______ ______ are the first pair of glands in the male system and contribute the most fluid to add to the sperm in the testes.
    seminal vesicles
  47. The absence of ______ in the paramesonephric (Mullerian) ducts allow the ______, ______ ______, and the ______ to begin to form.
    APH; uterus, uterine tubes, and the upper 1/3 of the vagina to form.
  48. Develop from progenitor tissues that appear during the sexually indifferent stage.
    External Genitalia
  49. In the XY embryo between 9-12 weeks, the penis is formed here.
    Genital Tubercle
  50. In the XY embryo, the urethra, prostate & bulbourethral glands are formed here.
    Urogenital Sinus
  51. In the XY embryo, the scrotum is formed here.
    Urogenital Folds
  52. ______ and ______ act to form the external genitalia in the XY (male) embryo.
    Testosterone and DHT
  53. In the XX (female) embryo between 9-12 weeks, development of the external genitalia is ______.
  54. In the XX (female) embryo, the clitoris is formed here.
    Genital tubercle
  55. In the XX (female) embryo, the lower 2/3 of the vagina is formed here.
    Urogenital sinus
  56. In the XX (female) embryo, the Labia minora and Labia majora are formed here.
    Urogenital folds
  57. BOTH descend from their original positions high up in the abdomen.
    Testes and Ovaries
  58. Descent of the testes and ovaries depend on the _______.
    gubernaculum (ligamentous cord)
  59. Descent of the testes begins in the ______ month.
  60. In the XY (male) embryo, _______ and ______ cause shortening of gubernaculum (ligamentous cord).
    Testosterone and APH
  61. The ______ are completely descended by birth (95%).
  62. ______ is the failure of the testes to descend.
  63. An error of sex determination, in this individual the autosomal testis determining genes (DMRT1, DMRT2 & SOX9) is defective and not suppressed by DAX1.
    XX (SRY-) Male
  64. An error of sex determination, in this individual the SRY gene is absent (translocation error during meiosis).
    XY (SRY-) Female
  65. An error of sex determination, in this individual the SRY gene is defective.
    XY (SRY+) Female
  66. An error of sex determination, in this individual the SRY gene acts on the X chromosome (translocation error during meiosis)
    XX (SRY+) Male
  67. In ______ ______, both ovarian & testicular tissue is present in the same individual (XX or XY).
    True Hermaphroditism
  68. In true hermaphroditism, the individual is most always ______.
  69. Formed by the yolk sac, then migrate from yolk sac to genital ridges and develop into germ cells (oogonia or spermatogonia)
    Primordial Germ Cells (PGC's)
  70. Arrival of ______ in genital ridges stimulates conversion of the indifferent gonad into a testis or ovary.
  71. Steroidogenic cells that secrete testosterone.
    Leydig Cells
  72. Supporting cells that secrete APH
    Sertoli Cells
  73. Steroidogenic cells that synthesize androgens
    Theca cells
  74. Supporting cells that convert androgens to estrogen
    Follicle (Granulosa) cells
  75. Chromosome pairs 1-22 are referred to as:
  76. Formation of the ovaries requires which
    of the following?
    The absence of the SRY Gene

    The DAX1 gene on each of the X chromosomes to suppress DMRT1, DMRT2, and SOX9 genes
  77. The migration of ____________from the ____________ into the genital ridge of the embryo around the 4-5th  week, begins
    gonadal differentiation.
    Primordial Germ Cells (PGC’s); yolk sac
  78. Around the 7th week in the XY embryo, the 2 cell types of the genital ridge will form the
    testes.  What cells of the testes will the supporting cells become?
    Sertoli cells
  79. What hormone will the Leydig cells secrete?
  80. Around the 10th week in the XX embryo, the 2 cell types of the genital ridge will form the
    ovaries.  What cells of the testes will the steroidogenic cells become?
    Theca cells
  81. Internal genitalia will form the
    mesonephric and paramesonephric ducts
  82. The Paramesonephric duct is also referred to as the _________ duct.
  83. What internal genitalia will form in the female from the paramesonephric duct?
    uterine tube
  84. What hormones are required for the internal genitalia of the female to form?
    No hormones
  85. External genitalia will form the
    genital tubercle, urogenital sinus, and urogenital folds
  86. What is necessary in order for the urogenital sinus to form the urethra in the XY embryo?
    DHT (dihydrotestosterone)
  87. The urogenital folds form the ______________ in males and the ______________ in females.
    scrotum; labia
  88. What progenitor tissue later becomes the penis in males and the clitoris in the female?
    genital tubercle
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Chapter 5: Sex Determination & Fetal Sexual Differentiation
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