Sex Determination and Testis Development

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Questions and Answers

What is the primary role of the SRY gene during sexual differentiation?

  • To control the migration of primordial germ cells
  • To initiate the cascade resulting in male sexual differentiation (correct)
  • To promote ovary development in XX embryos
  • To regulate hormone secretion from the adrenal glands

What is the fate of the medulla in XX embryos?

  • It regresses while the cortex develops into the ovary (correct)
  • It forms a structure identical to the vas deferens
  • It converts to mesonephric ducts
  • It develops into the testes

Which cells produce testosterone and play a critical role in male differentiation?

  • Follicular cells
  • Primordial germ cells
  • Sertoli cells
  • Leydig cells (correct)

Which of the following structures forms as a result of the retention of Wolffian ducts in males?

<p>Vas deferens (D)</p> Signup and view all the answers

What occurs when mutations in the SOX 9 gene are present?

<p>Sex reversal (A)</p> Signup and view all the answers

The primordial germ cells migrate to which location during development?

<p>Yolk sac endoderm (C)</p> Signup and view all the answers

What is the role of the WT-1 gene in gonadal development?

<p>It functions in urogenital ridge determination (A)</p> Signup and view all the answers

DAX-1 is involved in which aspect of sex determination?

<p>Promoting the development of ovary structures (C)</p> Signup and view all the answers

What influences the formation of efferent ductules from the mesonephros tubules?

<p>Testosterone (D)</p> Signup and view all the answers

What structure do the mesonephric ducts develop into in males?

<p>Vas deferens (A)</p> Signup and view all the answers

In the absence of testosterone, which ducts degenerate in females?

<p>Mesonephric ducts (A)</p> Signup and view all the answers

Which structure is formed by the caudal fusion of the Müllerian ducts?

<p>Uterovaginal canal (C)</p> Signup and view all the answers

What does the unfused cranial portion of the paramesonephric ducts develop into?

<p>Fallopian tubes (A)</p> Signup and view all the answers

What forms a slight thickening on the posterior wall of the pelvic urethra?

<p>Sinusal tubercle (A)</p> Signup and view all the answers

Which part of the uterus is contributed by the superior aspect of the uterovaginal canal?

<p>Endometrium (C)</p> Signup and view all the answers

What separates the vagina and urinary system during development?

<p>Sinusal bulbs (C)</p> Signup and view all the answers

What hormone is secreted by Sertoli cells that maintains germ cells in meiotic arrest?

<p>Anti-müllerian hormone (D)</p> Signup and view all the answers

Which cells give rise to sperm after puberty?

<p>Primordial germ cells (D)</p> Signup and view all the answers

What structure serves as the precursor to the seminiferous tubules in the male gonad?

<p>Gonadal cords (A)</p> Signup and view all the answers

What happens to primordial germ cells during their association with the developing seminiferous tubules?

<p>They remain inactive as spermatogonia. (A)</p> Signup and view all the answers

Which hormone is responsible for the differentiation of mesenchymal cells into Leydig cells?

<p>Anti-müllerian hormone (A)</p> Signup and view all the answers

What is the primary function of Sertoli cells in the seminiferous tubules?

<p>Support and nourish developing sperm cells (D)</p> Signup and view all the answers

During embryonic development, what event occurs when the primary sex cords enter the medulla?

<p>Differentiation into seminiferous cords (B)</p> Signup and view all the answers

At what stage do the seminiferous tubules begin to form?

<p>After the 6-week embryonic stage (D)</p> Signup and view all the answers

What must happen to the released egg at maturity since there is no contact with the ovarian follicles during development?

<p>It must be caught by the fimbria of the fallopian tube. (A)</p> Signup and view all the answers

During which week of development does the elongation of the genital tubercle begin in males?

<p>Tenth week (D)</p> Signup and view all the answers

What are the components from which the external genitalia form during development?

<p>Labioscrotal folds and genital tubercle (A)</p> Signup and view all the answers

How are the external genitalia structured in males and females until about the eighth week of development?

<p>Similar in structure (C)</p> Signup and view all the answers

Which hormone is crucial for the morphological changes during the formation of male external genitalia?

<p>Dihydrotestosterone (DHT) (B)</p> Signup and view all the answers

What structure is formed from the fusion of the urogenital folds in males?

<p>Urethra (C)</p> Signup and view all the answers

What is formed from the labioscrotal folds during male genital development?

<p>Scrotum (B)</p> Signup and view all the answers

Where do the paramesonephric ducts fuse during female reproductive development?

<p>Near their attachment to the posterior wall of the primitive urogenital sinus (B)</p> Signup and view all the answers

What condition is characterized by 46 XY individuals who are poorly virilized due to insufficient testosterone production?

<p>Androgen insufficiency syndrome (A)</p> Signup and view all the answers

What is the term for the condition where there is an inability to convert testosterone to dihydrotestosterone?

<p>5 alpha-reductase deficiency (A)</p> Signup and view all the answers

What is the genetic pattern associated with androgen insufficiency syndrome?

<p>Autosomal recessive (A)</p> Signup and view all the answers

Which hormone is primarily involved in the development of male secondary sex characteristics during puberty for those with 5 alpha-reductase deficiency?

<p>Testosterone (A)</p> Signup and view all the answers

What is the result of diminished response to dihydrotestosterone at the end organ in 46 XY individuals?

<p>Development of female secondary sex characteristics (C)</p> Signup and view all the answers

What do the genital folds and swellings of a person with end organ insensitivity syndrome appear like?

<p>Female (D)</p> Signup and view all the answers

In cases of 5 alpha-reductase deficiency, what happens when testosterone production begins at puberty?

<p>Individuals develop male secondary sex characteristics (B)</p> Signup and view all the answers

What is a critical intervention that can be performed for a child with androgen insufficiency syndrome?

<p>Hormone replacement therapy (D)</p> Signup and view all the answers

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Study Notes

Sex Determination

  • SRY gene on the Y chromosome initiates male sexual differentiation
  • SOX9 gene on the autosome is structurally related to SRY and important for testes differentiation
  • Mutations in SOX9 can result in sex reversal
  • WT-1 gene is a transcription factor involved in urogenital ridge determination
  • Wolffian ducts develop into male internal genitalia
  • Paramesonephric ducts develop into female internal genitalia
  • Primordial germ cells (PGCs) are the precursors for gametes (sperm and eggs)
  • PGCs migrate from the epiblast to the gonadal ridge

Testis Development

  • SRY gene activates the transcription factor SOX9
  • SOX9 promotes the development of the male gonad - testes
  • The primary sex cords in the medullary region of the developing testis differentiate into seminiferous tubules
  • Leydig cells are derived from mesenchyme and secrete testosterone
  • Sertoli cells develop from the primary sex cords and produce anti-Mullerian hormone (AMH)
  • Testosterone promotes Wollfian duct differentiation and AMH causes regression of the Mullerian ducts.
  • The testes produce testosterone leading to the development of the epididymis and vas deferens

Ovary Development

  • In the absence of SRY, the cortex of the gonadal ridge develops into the ovary
  • The medulla of the gonadal ridge regresses
  • The paramesonephric ducts differentiate into the fallopian tubes, uterus, and upper vagina
  • The sinusal tubercle forms a thickening in the posterior wall of the pelvic urethra.
  • The sinusal bulbs develop from it, separating the vagina from the urinary system

External Genitalia

  • Genital tubercle, labrioscrotal folds and genital fold develop the external genitalia
  • In males:
    • Genital tubercle elongates and forms the penis
    • Fusion of genital folds forms the penile urethra
    • Labrioscrotal folds develop into the scrotum.
  • In females:
    • Genital tubercle forms the clitoris
    • Genital folds develop into the labia minora
    • Labrioscrotal folds develop into the labia majora

Sex Reversal

  • Male pseudohermaphroditism: occurs when 46 XY individuals have poorly virilized genitalia
  • Causes of Pseudohermaphroditism:
    • Androgen insensitivity syndrome: Insensitivity to androgens (T and DHT) at the end organ; leads to female-like genitalia.
    • 5 alpha-reductase deficiency: The inability to convert testosterone to dihydrotestosterone (DHT); leads to female-like genitalia until puberty when testosterone levels increase.
    • Androgen insufficiency syndrome: Insufficient production of testosterone; leads to underdeveloped male genitalia.
  • Aromatase converts testosterone to estradiol.

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