The mesonephric duct is a paired organ found in mammals including humans during embryogenesis. Wolffian structures are male urogenital structures that include the epididymis, vas deferens, the mesonephric duct connects the primitive kidney, the mesonephros, to the cloaca and serves as the anlage for certain male reproductive organs. The mesonephric duct connects the primitive kidney, the mesonephros, to the cloaca, in both the male and the female the mesonephric duct develops into the trigone of urinary bladder, a part of the bladder wall. However, further development differentiates between the sexes in the development of the urinary and reproductive organs. In a male, it develops into a system of connected organs between the efferent ducts of the testis and the prostate, namely the epididymis, the vas deferens, the prostate forms from the urogenital sinus and the efferent ducts form from the mesonephric tubules. For this it is critical that the ducts are exposed to testosterone during embryogenesis, testosterone binds to and activates androgen receptor, affecting intracellular signals and modifying the expression of numerous genes. In the mature male, the function of system is to store and mature sperm. In the female, with the absence of anti-Müllerian hormone secretion by the Sertoli cells and subsequent Müllerian apoptosis, the Wolffian duct regresses, the epoophoron and Skenes glands may be present. Also, lateral to the wall of the vagina a Gartners duct or cyst could develop as a remnant and it is named after Caspar Friedrich Wolff who described the mesonephros and its ducts in his dissertation in 1759
Diagrams to illustrate the changes in the cloaca in mammals during development. A, early embryonic stage, showing the cloaca receiving the urinary bladder, the rectum, and the Wolffian duct, as in the lower vertebrates. B, later stage, showing the beginning of the fold which divides the cloaca into a ventral urogenital sinus which receives the urinary bladder, Wolffian ducts, and ureters, and into a dorsal part which receives the rectum. C, further progress of the fold, dividing the cloaca into urogenital sinus and rectum; the ureter has separated from the Wolffian duct and is shifting anteriorly. D, completion of the fold, showing complete separation of the cloaca into ventral urogenital sinus and dorsal rectum.
Transverse section of a chick embryo of forty-five hours' incubation.
Wolffian duct (red) degenerates in females (middle image) and develops in males (bottom).