. The development of the human body : a manual of human embryology. Embryology; Embryo, Non-Mammalian. THE MESONEPHROS 341 glomeruli, such as occur in connection with the mesonephric tubules do not occur in the pronephros of the human embryo, and this fact, together with the presence of external glomeruli and the participa- tion of the tubules in the formation of the Wolffian duct, serve to distinguish the pronephros from the mesonephros. The pronephric tubules, are, as has been stated, transitory structures and by the time the embryo has reached a length of about 5 mm. they have all disappear
. The development of the human body : a manual of human embryology. Embryology; Embryo, Non-Mammalian. THE MESONEPHROS 341 glomeruli, such as occur in connection with the mesonephric tubules do not occur in the pronephros of the human embryo, and this fact, together with the presence of external glomeruli and the participa- tion of the tubules in the formation of the Wolffian duct, serve to distinguish the pronephros from the mesonephros. The pronephric tubules, are, as has been stated, transitory structures and by the time the embryo has reached a length of about 5 mm. they have all disappeared. Before their disappearance is complete, however, a second series of tubules has commenced to develop, forming what is termed the mesonephros or Wolffian body. The Development of the Mesonephros.—The pronephric duct does not disappear with the degeneration of the pronephric tubules, but persists to serve as the duct for the mesonephros and to play an important part in the development of the metanephros also. In the Wolffian ridge there appear in embryos of between 3 and 4 mm. a number of coiled tubules, which arise by some of the cells of the ridge aggregating to form solid cords, at first en- tirely unconnected with either the coelomic epithelium or the Wolffian duct. Later the cords become connected with the cce- lomic epithelium and acquire a lumen, and near the coelomic end of the tubule, at a region corresponding to the chamber of a pro- nephric tubule, a condensation of the mesenchyme of the Wolffian ridge occurs to form a glomerulus into which a branch extends from the neighboring aorta. The tubules finally acquire connection with the Wolffian duct and at the same time lose their connections with the coelomic epithelium, their nephrostomes being accordingly but transitory structures. The tubules rapidly increase in length and. Fig. 210.—Transverse Section of the Wolffian Ridge of a Chick Em- bryo of Three Days. ao, Aorta; gl, glomerulus; gr, genital ridge; mes, me
Size: 1623px × 1540px
Photo credit: © Central Historic Books / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookautho, bookcentury1900, bookdecade1910, booksubjectembryology
