One of three excretory organs appearing in the evolution of vertebrates; in life forms with a metanephros, the m. is located between the regressing pronephros and the metanephros, cephalic to the latter. In young mammalian embryos, the m. is well developed and briefly functional until establishment of the metanephros, the definitive kidney; in older embryos, the m. undergoes regression as an excretory organ, but its duct system is retained in the male as the epididymis and ductus deferens. SYN: middle kidney, wolffian body. [meso- + G. nephros, kidney]
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me·so·neph·ros .mez-ə-'nef-rəs, .mēz-, .mēs-, .mes-, -.räs n, pl -neph·roi -.rȯi either member of the second and midmost of the three paired vertebrate renal organs that functions in adult fishes and amphibians but functions only in the embryo of reptiles, birds, and mammals in which it is replaced by a metanephros in the adult called also Wolffian body compare PRONEPHROS
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n.
the second area of kidney tissue to develop in the embryo. Its excretory function only lasts for a very brief period before it degenerates. However, parts of it become incorporated into the male reproductive structures. Its duct - the mesonephric (or Wolffian) duct - persists in males as the epididymis and vas deferens, which conduct sperm from the testis.
• mesonephric adj.
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meso·neph·ros (mez″o-) (me″zo-nefґros) pl. mesonephґroi [meso- + Gr. nephros kidney] the excretory organ of the embryo, arising caudad to the pronephros or pronephric rudiments and using its duct; it consists of a long tube in the lower part of the body cavity, running parallel with the vertebral axis and joined at right angles by a row of twisting tubes. See also metanephros. Called also mesonephron, middle kidney, and wolffian body. mesonephric adjMedical dictionary. 2011.