Bacteriology USMLE Step 1 Practice Question

A 15-year-old girl presents to your clinic with primary amenorrhea. She reports normal pubertal development with breast development beginning at age 12 and pubic hair development at age 13. She denies vaginal bleeding, abdominal pain, or cyclic symptoms. Her vital signs are normal. On physical examination, she has normal external genitalia, Tanner stage 5 breast development, and Tanner stage 5 pubic hair. Laboratory studies reveal normal FSH, LH, and estrogen levels. Pelvic ultrasound demonstrates bilateral normal-appearing ovaries, a normal cervix, and a normal upper vagina, but an absent uterus. Which of the following embryologic structures is responsible for the absent uterus in this patient?