Sex Determination and Genital Development

What is the role of the SRY gene?

Located on the Y chromosome; its expression triggers testis development and androgen production, initiating male phenotypic development

What do mesonephric and paramesonephric ducts become?

Mesonephric ducts form most male ducts (e.g., epididymis, vas deferens); paramesonephric ducts form female structures (uterine tubes, uterus, superior vagina)

How do internal genitalia develop in males?

SRY expression (around week 7) leads to testis formation; sustentacular cells secrete anti-Müllerian hormone causing paramesonephric duct degeneration; mesonephric ducts develop into male ducts (weeks 8–12)

How do internal genitalia develop in females?

Absence of SRY allows paramesonephric ducts to persist and form uterine tubes, uterus, and superior vagina; mesonephric ducts degenerate

How do external genitalia differentiate?

Same primordial structures until ~week 12; in presence of testosterone male structures form (penis, fused scrotum); absence of testosterone yields female structures (clitoris, labia minora and majora)

What is the gubernaculum?

Connective tissue band that guides testis descent from abdomen to scrotum, completed by the ninth month