A genital tubercle is a body of tissue which forms in the ventral, caudal region of mammalian embryos of both sexes, and eventually develops into a phallus. In the human fetus the genital tubercle develops around week 4 of gestation, and by week 9 becomes recognizably either a clitoris or penis.
The genital tubercle is sensitive to dihydrotestosterone and rich in 5-alpha-reductase , so that the amount of fetal testosterone present after the second month is a major determinant of phallus size at birth.
See also