Reproductive System: Session 1 - Origin of the Sexes
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Questions and Answers

What is the term used to describe an embryo that is not yet differentiated into male or female?

Indifferent embryo

The gonads develop in a ridge of intermediate mesoderm called the urogenital ridge.

True

Where do primordial germ cells arise from in the early embryo?

The lining cells in the wall of the yolk sac

Which of these weeks marks the complete phenotypic differentiation in the embryo?

<p>Week 20</p> Signup and view all the answers

What gene determines the phenotypic differentiation of the embryo?

<p>Sry gene</p> Signup and view all the answers

What are the two types of cells that differentiate in the testes to produce testosterone and Mullerian-inhibiting factor (MIF)?

<p>Leydig cells and Sertoli cells</p> Signup and view all the answers

The presence of TDF, testosterone, and MIF leads to the development of a female phenotype.

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

Which of these structures are remodeled during development to form the adult female and male reproductive systems?

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

What process involves the gubernaculum and the processus vaginalis?

<p>Descent of the ovaries and testes</p> Signup and view all the answers

What condition results when the testes fail to descend into the scrotum?

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

What two structures are crucial for the formation of the uterus and vagina in females?

<p>Paramesonephric ducts and sinovaginal bulbs</p> Signup and view all the answers

What is the condition where the urethral opening is located on the underside of the penis?

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

What is the condition causing the male urethra to open on the dorsal surface of the penis?

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

The prostate gland develops from multiple outgrowths of the prostatic urethra.

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

Which hormone plays a primary role in the growth of the prostate gland in males?

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

Study Notes

Reproductive System: Session 1 - Origin of the Sexes

  • Embryos, during weeks 1-6, are phenotypically indistinguishable, despite having established XX or XY genotypes at fertilization.
  • By week 12, external genitalia characteristics become discernible.
  • Phenotypic differentiation is complete by week 20.

Indifferent Embryo

  • Gonads develop within a longitudinal elevation, called the urogenital ridge, from intermediate mesoderm.
  • Primordial germ cells originate from yolk sac lining cells (weeks 3-4).
  • At weeks 4-6, primordial germ cells migrate to the indifferent gonad.

Male Development

  • Male germ cells colonize the medullary region of the gonad.
  • The cortex region of the gonad atrophies.
  • Presence of the Y chromosome triggers SRY gene activity, leading to testis-determining factor (TDF).

Female Development

  • Female germ cells colonize the cortex region of the gonad, preventing medullary cord development.

Phenotypic Differentiation

  • Sry gene, located on the short arm of the Y chromosome, dictates phenotypic sex.
  • The Sry gene encodes for TDF (testis-determining factor).
  • In the presence of TDF, testosterone and Mullerian-inhibiting factor (MIF) guide development toward a male phenotype.
  • In the absence of TDF, testosterone, and MIF, the embryo develops into a female phenotype.

Components of Indifferent Embryo

  • Gonads
  • Paramesonephric (Mullerian) duct
  • Mesonephric (Wolffian) duct
  • Phallus
  • Urethral folds
  • Genital swellings

Development of Prostate Gland

  • The prostate gland arises from multiple outgrowths of the prostatic urethra.
  • Dihydrotestosterone (DHT) is the primary mediator of prostatic growth in males.

External Genitalia (Indifferent Stage)

  • The external genitalia exhibit an undifferentiated structure, characterized by:
    • Genital tubercle
    • Genital swelling
    • Cloacal fold
    • Cloacal membrane

External Genitalia in the Male:

  • Development stages involving the Phallus, Urethral groove and folds, scrotal swellings, and perineum.
  • Precise details of the structures and their formation are outlined in the diagrams.

External Genitalia in the Female

  • The external structure of the genitalia is detailed in the embryo in both stages of development, 5 months and newborn, including the Urogenital groove,Urethral folds, Genital swelling and the labia.

Descent of Ovary and Testes

  • Although the ovaries and testes initially develop in the abdominal cavity, they eventually descend to the pelvis (ovaries) and scrotum (testes).
  • The gubernaculum, a fibrous band , guides the descent; The processus vaginalis also plays a role in the process .

Hypospadias and Epispadias

  • Hypospadias and epispadias represent abnormalities in the development of the urethra, resulting in abnormal urethral openings.
  • Epispadias often involves associated exstrophy of the bladder.

Other Key Information

  • Slides also give diagrams depicting the development stages.
  • The development of the uterus and vagina is also addressed, along with potential abnormalities in development.

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Related Documents

Reproductive System Embryology PDF

Description

Explore the early stages of human sexual differentiation in this quiz, focusing on embryonic development from conception to week 20. Learn about the roles of the Y chromosome, SRY gene, and the migration of primordial germ cells in male and female development.

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