Development of reproductive tracts Flashcards
How is the development of the GI tract and urogenital tract linked?
- At the beginning, GI tract and urinary tract share a common caudal opening
- Hindgut ends in a dilated structure called the cloaca
- Cloaca becomes urogenital sinus - the common opening for the reproductive and urinary systems
What determines the chromosomal sex of an embryo?
- Whether the sperm that fertilises the oocyte is X or Y
What is the indifferent stage of development?
- Initial step that is the same in males and females
- Primordial germ cells migrate along retroperitoneum to the gonad at the urogenital ridge
What are primordial germ cells?
- Precursors of gametes
- Originate in the endoderm of the yolk sac and migrate to the genital ridge to form the indifferent gonad
What are the primitive sex cords?
- Epithelium of the genital ridge proliferates and penetrates the intermediate mesoderm to form the primitive sex cords
What forms the indifferent gonad?
- Combination of germ cells and primitive sex cords forms the indifferent gonad
- Development of ovaries or testes can occur from here
What determines whether the indifferent gonad develops into ovaries or testes?
- Y chromosome
- Contains SRY gene - this is the testos determining factor
- Presence of SRY = male development occurs
- Absence of SRY = female development occurs
How does the SRY gene cause the testes to develop?
- Stimulates development of primitive sex cords to form testis cords
- Tunica albuginea forms around the cords
- Portion of testis cord breaks off to form future rete testis
- Remaining cord contains germ cells and Sertoli cells
- Leydig cells begin to produce testosterone at week 8
How does an absence of the SRY gene cause the ovaries to develop?
- Primitive sex cords degenerate
- Testis cords do not form
- Epithelium of gonad continues to proliferate, producing cortical cords
- Cord surrounds germ cells to form primordial follicle
What are the names given to the ducts of the male and female ducts of the reproductive tracts?
- Wolffian duct (mesonephric) - males
- Mullerian duct (paramesonephric) - females
What determines the fates of the Wolffian and Mullerian ducts in males?
- Testis produces Mullerian Inhibiting Hormone (MIH)
- Supresses mullerian duct development
- Testis also produces androgens
- Supports Wolffian duct
What determines the fates of the Wolffian and Mullerian ducts in females?
- No testis producing MIH
- No suppression of Mullerian duct development
- No androgens produced
- Wolffian duct degenerates
Why is the Wolffian duct initially needed in both male and female embryos?
- Acts as the duct for the embryonic kidney
- Drains into urogenital sinus
- No longer needed once true kidney develops
What is the fate of the Wolffian duct?
- Converted into vas deferens and epididymis
- Migrates with testis as it descends
How does the Mullerian Duct develop?
- Mullerian duct develops appears as invaginations of the epithelium of the urogenital ridge
- Caudally: makes contact with cloaca
- Cranially: opens into abdominal cavity
