Mesonephros


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Related to Mesonephros: metanephros, mesonephric duct

mesonephros

[¦mez·ə′ne‚frōs]
(embryology)
One of the middle of three pairs of embryonic renal structures in vertebrates; persists in adult fish and is replaced by the metanephros in higher forms.

Mesonephros

 

wolffian body, a paired excretory organ in vertebrates.

The mesonephros consists of numerous twisting tubules that open at one end into the body cavity and at the other into the mesonephric (wolffian) duct. Each tubule has a lateral outgrowth —the malpighian corpuscle. In fish and amphibians, the mesonephros functions throughout life; in reptiles, birds, and mammals, including man, it functions only during the early stages of embryonic development, being subsequently replaced by the metanephros. At first the metanephros is metameric in structure, but this is lost as the organism grows. In the males of higher vertebrates, most of the mesonephros becomes an appendage of the testis and, with the wolffian duct, forms the vas deferens; in the females, the mesonephros is reduced.

References in periodicals archive ?
Am, amniotic cavity; db, decidua basalis; L, Labyrinth; Mt, metanephros; Ms, mesonephros. Haematoxylin and Eosin stain, B&D (scale bar=100[micro]m).
The first one matches with the present study giving that stages HH14 to HH18 occur during day 3 of development and is related to changes that include the amnion, heart and circulatory system formation; the second peak matches the days 4 and 5 of incubation and is related to possible alterations in the formation of the visceral arches (10), the corion and allantois fusion and the beginning of the functioning of the mesonephros (3).
of the proximal tubules of mesonephros decreased among the groups with significant difference between control group I and all the experimental groups.
longitudinal division of the urogenital ridge, incomplete degeneration of a part of the mesonephros and development of peritoneal bands have been suggested, but none can explain all types of polyorchidism.[2] Polyorchidism classification also shows considerable variation between reports.
In similar times, the migration of the primordial germinal cells from the yolk sac leads to the formation of ovaries which arise from mesenchyme and from the epithelium of genital crest of the intermediate mesoderm, with female reproductive tract organogenetic processes different from those of mesonephros; therefore, the anomalies of Mullerian ducts are not associated, generally, with anomalies of ovary development [169].
(22-25) Deletion of both PAX8 and PAX2 genes prevents generation of the mesonephric (wolffian) duct and subsequent formation of all three embryonic kidneys (pronephros, mesonephros, and metanephros).
Left and right gonads were visualized using a Nikon SMZ-U dissecting microscope (Nikon Instruments, Melville, NY), separated from adjacent mesonephros, and transferred to individual labeled wells of ice-cold transport media until xenografting.
The renal corpuscle and efferent epididymal ducts represent the remnant mesonephros that is modified for sperm transport.
In dorsal mesonephros, primary metanephros kidneys were located (Figure 1) so this structure in fetus that CRL was 30 mm also was observed adhered in their vicinity under vertebral column (Figure 2,3).
Pour sa part, l' endocrinon (systeme endocrinien) regroupe toutes les glandes a secretion interne plus les organes dits recapitulatifs de l'ontogenese: la chorde, les reins embryonnaires, le protonephros et le mesonephros. "Ces organes ne sont donc pas des vestiges illustrant la loi biogenetique fondamentale; ils participent activement au developpement de la forme de l'individu pendant un laps de temps bien delimite, comme c'est le cas par exemple pour le thymus." (10)