B Production of müllerian-inhibitory substance by the embryonic testes
The uterine tubes develop from the cranial portions of the müllerian (paramesonephric) system. In the males these ducts regress under the influence of müllerian-inhibitory substance (MIS). MIS is secreted by the Sertoli cells of the embryonic testes. If the MIS is not secreted in adequate quantities by the embryonic testes, the müllerian ducts will develop into the female genitals. This does not disturb the development of the male genitalia. So, failure to secrete MIS (or an abnormality in the receptor for MIS) can result in a genetic male with testes and normal male phenotypic development, but additionally, uterine tubes, a uterus, and an upper vagina.
Production of testosterone by the embryonic testes is necessary for the development of the wolffian duct system derivatives (e.g., vas deferens) in the male. Testosterone however, does not cause regression of the müllerian system.