. Chordate anatomy. Chordata; Anatomy, Comparative. THE UROGENITAL SYSTEM 319 Minor calyces arise by the continued subdivision and branching of the major calyces. Further branching to the twelfth generation produces the collecting tubules and the medullary portion of the kidney. Those of the fifth generation to the number of twenty to eighty for each renal calyx become the papillary ducts which convey urine from the collecting tubules and which open directly into each of the renal calyces. (Fig. 283). Fig. 284.—Schematic diagrams to show the relations of pronephros, mesonephros, and metanephro
. Chordate anatomy. Chordata; Anatomy, Comparative. THE UROGENITAL SYSTEM 319 Minor calyces arise by the continued subdivision and branching of the major calyces. Further branching to the twelfth generation produces the collecting tubules and the medullary portion of the kidney. Those of the fifth generation to the number of twenty to eighty for each renal calyx become the papillary ducts which convey urine from the collecting tubules and which open directly into each of the renal calyces. (Fig. 283). Fig. 284.—Schematic diagrams to show the relations of pronephros, mesonephros, and metanephros at various stages of development. In the adult male the mesonephric (Wolffian) duct is retained as the ductus deferens. (From Patten's " Embryology of the ;) Each of the collecting tubules terminates in a slight swelling or vesicu- lated enlargement, upon which a mass of nephrogenic tissue rests as a cap. From this mass arise excretory tubules, which subsequently acquire connexion with the collecting tubule. (Fig. 283) Differentiation of the excretory tubules begins with the formation of vesicular cell-clusters which separate from the remaining nephrogenic tissue. These vesicles elongate into excretory tubules and their ends enlarge to form Bowman's Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Neal, Herbert V. (Herbert Vincent), 1869-1940; Rand, Herbert W. (Herbert Wilbur), 1872-1960. Philadelphia : P. Blakiston's Son & Co.
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