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{{short description|Paired organ of the urogenital system in mammals}}
{{Infobox embryology
| Name = Mesonephric duct
| Latin = ductus mesonephricus; ductus Wolffi
| Image = Gray1109.png
| Caption = [[Urogenital sinus]] of female human [[embryo]] of eight and a half to nine weeks old
| Image2 =
| Caption2 =
| System =
| Days = 28
| CarnegieStage = 11
| Precursor = [[Intermediate mesoderm]]
| GivesRiseTo = [[vas deferens|Vasa deferentia]], [[seminal vesicles]], [[epididymis|epididymides]], [[Gartner's duct]]
}}
The '''mesonephric duct''', also known as the '''Wolffian duct''', '''archinephric duct''', '''Leydig's duct''' or '''nephric duct''', is a paired [[Organ (anatomy)|organ]] that develops in the early stages of [[embryonic development]] in humans and other mammals. It is an important structure that plays a critical role in the formation of [[male reproductive organs]]. The duct is named after [[Caspar Friedrich Wolff]], a German [[physiologist]] and [[embryologist]] who first described it in 1759.<ref name="auto">{{WhoNamedIt|synd|2845}}</ref>

During embryonic development, the mesonephric ducts form as a part of the [[urogenital system]].<ref>{{cite book |doi=10.1016/b978-0-12-405945-0.00027-2 |chapter=Development of the Genital System |title=Principles of Developmental Genetics |date=2015 |last1=Du |first1=Hongling |last2=Taylor |first2=Hugh S. |pages=487–504 |isbn=978-0-12-405945-0 }}</ref>

== Structure ==
The mesonephric duct connects the primitive kidney, the ''[[mesonephros]]'', to the [[Cloaca (embryology)|cloaca]]. It also serves as the [[primordium]] for male [[urogenital]] structures including the [[epididymis|epididymides]], [[vas deferens|vasa deferentia]], and [[seminal vesicle]]s.

== Development ==
In both males and females, the mesonephric ducts develop into the [[trigone of urinary bladder]], a part of the bladder wall, but the sexes differentiate in other ways during development of the [[Development of the urinary system|urinary]] and [[Development of the reproductive system|reproductive]] organs.

=== Male ===

In a [[male]], they develop into a system of connected organs between the [[efferent ducts]] of the [[testis]] and the prostate, namely the [[epididymis]], the [[vas deferens]], and the [[seminal vesicle]]. The [[prostate]] forms from the [[urogenital sinus]] and the efferent ducts form from the [[mesonephric tubules]].

For this, it is critical that the ducts are exposed to [[testosterone]] during [[embryogenesis]]. Testosterone binds to and activates [[androgen receptor]], affecting intracellular signals and modifying the expression of numerous genes.<ref name="pmid16567946">{{cite journal |last1=Hannema |first1=Sabine E. |last2=Print |first2=Cristin G. |last3=Charnock-Jones |first3=D. Stephen |last4=Coleman |first4=Nick |last5=Hughes |first5=Ieuan A. |title=Changes in gene expression during Wolffian duct development |journal=Hormone Research |date=2006 |volume=65 |issue=4 |pages=200–209 |id={{ProQuest|1233606874}} |doi=10.1159/000092408 |pmid=16567946 }}</ref>

In the mature male, the function of this system is to store and mature [[spermatozoon|sperm]], and provide accessory [[semen]] fluid.The mesonephric duct (precursor of the male reproductive system) forms around the 3-4th week of pregnancy, present before the paramesonephric duct (precursor of the female reproductive system).

=== Female ===

In the [[female]], with the absence of [[anti-Müllerian hormone]] secretion by the [[Sertoli cells]] and subsequent Müllerian [[apoptosis]], the mesonephric ducts regress, although inclusions may persist. The vestigial [[epoophoron]] arises from these ducts. Also, lateral to the wall of the vagina, a [[Gartner's duct]] could develop as a remnant. Normal regression starts with the action of [[COUP-TFII]] in the Woffian mesenchyme.<ref>{{cite journal |last1=Zhao |first1=F |last2=Grimm |first2=SA |last3=Yao |first3=HH |title=Molecular Actions Underlying Wolffian Duct Regression in Sexual Differentiation of Murine Reproductive Tracts. |journal=Sexual Development |date=2020 |volume=14 |issue=1–6 |pages=51–59 |doi=10.1159/000513878 |pmid=33684916 |pmc=8328876}}</ref>

The mesonephric duct produces [[WNT9B]], which is required for the elongation of the Müllerian/paramesonephric ducts (this happens before sex specification).<ref>{{cite journal |last1=Roly |first1=Zahida Yesmin |last2=Backhouse |first2=Brendan |last3=Cutting |first3=Andrew |last4=Tan |first4=Tiong Yang |last5=Sinclair |first5=Andrew H. |last6=Ayers |first6=Katie L. |last7=Major |first7=Andrew T. |last8=Smith |first8=Craig A. |title=The cell biology and molecular genetics of Müllerian duct development |journal=WIREs Developmental Biology |date=May 2018 |volume=7 |issue=3 |article-number=e310 |doi=10.1002/wdev.310|pmid=29350886 }}</ref>

The [[mesenchyme]] of the mesonephric duct is retained in female reproductive tissue after sexual differentiation. As the Woffian regresses, they undergo significant chromatin remodeling and move to surround the Müllerian. Cells from the Woffian mesenchyme occur in a layer around the inner epithelium, where the Müllerian mesenchyme cells also reside. The two can be distinguished by their gene expression profile: cells derived from the Woffian mesenchyme expresses [[Androgen receptor|AR]], while those from the Müllerian mesenchyme expresses [[AMHR2]]. Both types of mesenchyme become smooth muscle and fibroblasts. They appear quite evenly mixed in the oviduct, but remain clearly separated the uterus, with the Woffian mesenchyme settling in the [[Mesometrium|mesometrial]] side.<ref>{{cite journal |last1=Zhao |first1=F |last2=Grimm |first2=SA |last3=Jia |first3=S |last4=Yao |first4=HH |title=Contribution of the Wolffian duct mesenchyme to the formation of the female reproductive tract |journal=PNAS Nexus |date=September 2022 |volume=1 |issue=4 |article-number=pgac182 |doi=10.1093/pnasnexus/pgac182 |doi-access=free|pmid=36204418|pmc=9523451 }}</ref>

== Function ==

=== Sexual differentiation ===
{{Main|Sexual differentiation}}

==History==
It is named after [[Caspar Friedrich Wolff]] who described the [[mesonephros]] and its ducts in his [[dissertation]] in 1759.<ref name="auto"/>

==Additional images==
[[File:A laboratory manual for comparative vertebrate anatomy (1922) (20754316592).jpg|thumb|center|upright=3|Diagrams to illustrate the changes in the [[Cloaca (embryology)|cloaca]] in [[mammal]]s during development. '''A''', early embryonic stage, showing the cloaca receiving the urinary bladder, the rectum, and the Wolffian duct, as in the lower vertebrates. '''B''', later stage, showing the beginning of the fold which divides the cloaca into a ventral [[urogenital sinus]] which receives the [[urinary bladder]], Wolffian ducts, and [[ureter]]s, and into a dorsal part which receives the [[rectum]]. '''C''', further progress of the fold, dividing the cloaca into urogenital sinus and rectum; the ureter has separated from the Wolffian duct and is shifting anteriorly. '''D''', completion of the fold, showing complete separation of the cloaca into ventral urogenital sinus and dorsal rectum.]]

{{clear}}

<gallery widths="180px" heights="120px">
File:Gray29.png|Diagram of a transverse section, showing the mode of formation of the amnion in the chick
File:Gray986.png|Reconstruction of a human embryo of 17 mm
File:Gray992.png|Cloaca of human embryo from twenty-five to twenty-seven days old
File:Gray1116.png|Tail end of human embryo thirty-two to thirty-three days old
File:Gray1117.png|Tail end of human embryo; from eight and a half to nine weeks old
</gallery>

== See also ==
* [[Fetal genital development]]
* [[List of homologues of the human reproductive system]]
* [[Masculinization]]
* [[Müllerian duct]]
* [[Sexual differentiation]]

==References==
{{reflist}}

==External links==
* [https://web.archive.org/web/20150511135442/http://www.aboutkidshealth.ca/en/howthebodyworks/sexdevelopmentanoverview/sexualdifferentiation/pages/ductdifferentiation.aspx How the Body Works / Sex Development / Sexual Differentiation / Duct Differentiation] - [[The Hospital for Sick Children, Toronto|The Hospital for Sick Children (GTA - Toronto, Ontario, Canada)]]

== Further reading ==
* {{cite journal |last1=Crossen |first1=MJ |last2=Wilbourne |first2=J |last3=Fogarty |first3=A |last4=Zhao |first4=F |title=Epithelial and mesenchymal fate decisions in Wolffian duct development. |journal=Trends in Endocrinology and Metabolism |date=August 2023 |volume=34 |issue=8 |pages=462–473 |doi=10.1016/j.tem.2023.05.007 |pmid=37330364 |pmc=10524679}}

{{Sex determination and differentiation}}
{{Development of urinary and reproductive systems}}
{{Authority control}}

[[Category:Embryology of urogenital system]]

Mesonephric duct - Revision history

imported>NeLaS: /* top */Improved short description