Histogenesis and Organogenesis

Abstract

The development of the male accessory sex glands is intimately connected with the formation of the mesonephros, especially its excretory duct, the wolffian duct (Felix, 1911; Horstmann and Stegner, 1966; Oberndorfer, 1931; for review see Tiedemann, 1976). While in the human embryo the pronephros is only a transitory rudiment, the remnants of its canaliculi fuse in a craniocaudal direction and form a common duct, the primary ureter or wolffian duct, which joins the excretory canaliculi and terminates blind at the caudal ectoderm (Chwalla, 1927). The mesonephros, a functioning organ in various species (Tiedemann, 1976; Tiedemann and Schlüns, 1975), forms together with the developing gonad a fold of the dorsal abdominal cavity, the urogenital fold (Plica urogenitalis). This fold consists of (1) the genital fold (plica genitalis) containing the gonad and (2) the mesonephric ridge (plica mesonephridica) containing the müllerian and wolffian ducts. In the caudal parts of the embryo the mesonephric ridges of both sides fuse at their lateral aspects, after being rotated around a vertical axis by 180°. Thereby a frontal membrane is formed which terminates on the pelvic floor.