The mesonephric duct is a paired embryonic structure that develops as part of the mesonephros, the transient embryonic kidney.[1,2] It extends in a cranial-to-caudal direction along the dorsolateral aspect of the nephrogenic cord and connects to the cloaca in both male and female embryos.[1,2]  ​

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The mesonephric duct can be divided into three key components: 

1. Proximal Region: drains the mesonephros during early kidney development.[1]  

2. Middle Segment: contributes to the formation of the male genital tract under the influence of male sex hormones, including the epididymis.[3]

3. Distal Region: opens into the cloaca and later contributes to portions of the ejaculatory ducts in males.[2]  

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During development, the mesonephric duct lies lateral to the paramesonephric (Müllerian) duct. Expression of the SRY gene on the Y chromosome leads to production of testis-determining factor (TDF), which promotes testicular differentiation and maintenance of the mesonephric duct in genotypic male embryos.[1] Testosterone secreted by the developing testes further stimulates differentiation of the duct into male internal reproductive structures.[1] In genotypic female embryos, an absence of TDF and testosterone results in regression of the mesonephric duct, though remnants, such as Gartner’s duct, may persist.[1]