Definitions
from The American Heritage® Dictionary of the English Language, 5th Edition.
- noun The second of the three excretory organs that develop in a vertebrate embryo, becoming the functioning kidney in fish and amphibians but replaced by the metanephros in higher vertebrates.
from The Century Dictionary.
- noun Same as
mesonephron .
from the GNU version of the Collaborative International Dictionary of English.
- noun (Anat.) The middle one of the three pairs of embryonic renal organs developed in most vertebrates; the Wolffian body.
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- noun biology The second of the three
excretory organs of the developingembryo ; the Wolffian body
Etymologies
from The American Heritage® Dictionary of the English Language, 4th Edition
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Examples
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In fish and amphibia the kidney is derived directly from an embryonic organ known as the mesonephros, while in reptiles and mammals the mesonephros degenerates towards the end of embryonic life and plays no role in the formation of the adult kidney, which is formed instead from a discrete spherical mass of mesodermal tissue, the metanephros, which develops quite independently from the mesonephros.
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The tubules collectively constitute the mesonephros or Wolffian body (Figs. 986, 1107).
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These embryonic structures are on either side; the pronephros, the mesonephros, the metanephros, and the Wolffian and Müllerian ducts.
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At first the mesonephros and genital ridge are suspended by a common mesentery, but as the embryo grows the genital ridge gradually becomes pinched off from the mesonephros, with which it is at first continuous, though it still remains connected to the remnant of this body by a fold of peritoneum, the mesorchium or mesovarium (Fig. 1111).
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The metanephros arises in the intermediate cell mass, caudal to the mesonephros, which it resembles in structure.
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The testes, at an early period of fetal life, are placed at the back part of the abdominal cavity, behind the peritoneum, and each is attached by a peritoneal fold, the mesorchium, to the mesonephros.
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Later it becomes completely separated from the celomic epithelium and forms a suprarenal ridge projecting into the celom between the mesonephros and the root of the mesentery.
XI. Splanchnology. 1F. The Chromaphil and Cortical Systems 1918
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The tubules of the metanephros, unlike those of the pronephros and mesonephros, do not open into the Wolffian duct.
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The pronephros disappears very early; the structural elements of the mesonephros mostly degenerate, but in their place is developed the genital gland in association with which the Wolffian duct remains as the duct of the male genital gland, the Müllerian as that of the female; some of the tubules of the metanephros form part of the permanent kidney.
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From the front of the mesonephros a fold of peritoneum termed the inguinal fold grows forward to meet and fuse with a peritoneal fold, the inguinal crest, which grows backward from the antero-lateral abdominal wall.
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