Biological Systems MCAT Practice Exam

What structures do all embryos initially possess that contribute to the development of genitalia?

1. Wolffian ducts and Müllerian ducts

2. Fallopian tubes and uterine horns

3. Amniotic sac and yolk sac

4. Placenta and umbilical cord

The correct answer is: Wolffian ducts and Müllerian ducts

All embryos initially possess both Wolffian ducts and Müllerian ducts, which play crucial roles in the development of genitalia. These structures are part of the early reproductive system in embryos, and their fate is determined by the presence or absence of specific hormones. In male embryos, the presence of testosterone leads to the development of the Wolffian ducts into structures such as the vas deferens and seminal vesicles, while the Müllerian ducts regress. Conversely, in female embryos, without significant levels of testosterone, the Müllerian ducts develop into the fallopian tubes, uterus, and upper two-thirds of the vagina, while the Wolffian ducts regress. This shared early development underscores the bipotential nature of the gonadal system before the influence of sex determination factors, highlighting the significance of these ducts in the formation of either male or female genitalia. The other options presented do not reflect structures that directly develop into genitalia; for instance, the fallopian tubes and uterine horns are derivatives of the Müllerian ducts but are not present in all embryos initially. The amniotic sac and yolk sac, as well as the placenta and umbilical cord, serve different functions related to protection and nourishment rather than directly contributing to the development