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A kidney formed of nephric tubules arising in the middle region of the nephric ridge; a transient embryonic stage that replaces the pronephros, but is itself replaced by the adult metanephros [in mammals; in fishes and amphibians it is the adult kidney]. [Evolution, Fourth_Edition_(2006)_McGraw-Hill, Function, Kardong_KV, Vertebrates:_Comparative_Anatomy, p.745][VHOG], Organ that is the definitive adult kidney. It replaces the earlier pronephros, which degenerates as the mesonephros becomes functional in feeding stage tadpoles.[AAO]

By contrast to the pronephros, the histological features of the mammalian mesonephros, with its primitive glomeruli, suggest that it probably functions as a primitive kidney, and is involved in the production of much of the amniotic fluid. Within the two mesonephroi, one located on either side of the dorsal mesentery of the hindgut, a substantial number (in the region of about 40 or more) of cranio-caudally segmented mesonephric tubules are formed. It has, however, been suggested that only the most rostrally located 4-6 pairs of mesonephric tubules drain into the mesonephric portion of the nephric duct. This is now seen to extend along the length of the mesonephroi, being located towards their lateral sides. The mesonephros is also retained over a considerably longer period than the pronephros, but gradually undergoes regression in a cranio-caudal direction. While the rostral part displays clear evidence of regression its more caudal part appears to display evidence of functional activity. Within the medial part of the mesonephros, vesicles are formed, although no glomeruli are formed there in this species. It is, however, difficult to believe that the relatively enormous mesonephroi do not have an excretory role in the mouse, only serving as a base for gonadal differentiation. In the human embryo, the medial part of the mesonephric tubules enlarges, become invaginated by capillaries, and form glomeruli. These then take on an excretory role. In the mouse, the mesonephric ducts appear to be patent throughout their length[GUDMAP, modified]

uberon

middle kidney, corpus Wolffi, opisthonephros, opistonephros, opisto nephros, amphibian adult kidney

mesonephric

As the pronephros regresses, the archinephric duct induces the sequential differentiation of tubules in the more caudal parts of the nephric ridge. (...) Tubules that differentiate in the middle part of the nephric ridge form a kidney called the mesonephros. This kidney functions in the embryos and larvae of all vertebrates. (...) In all vertebrate embryos, the kidney begins with the differentiation of a few renal tubules from the anterior end of the nephric ridge overlying the pericardial cavity. (...) This early-developing embryonic kidney is called the pronephros.[well established][VHOG]

UBERON:0000080

In mammals, the mesonephros is the second of the three embryonic kidneys to be established and exists only transiently. In fish and amphibians, the mesonephros will form the mature kidney

• metanephros

• seminal vesicle

• mesonephric epithelium
• mesonephric S-shaped body
• mesonephric mesenchyme
• mesonephric nephron
• mesonephric glomerulus
• mesonephric comma-shaped body
• mesonephric smooth muscle tissue
• mesonephric capsule
• mesonephric nephron progenitor