Urinary duct

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The urinary duct ( Latin ductus mesonephricus ) is one of those embryonic genital structures that are present in both sexes , alongside the Müller duct ( Latin ductus paramesonephricus ) and plays an important role in sex differentiation . The urinary duct is also known as the primary ureter or Wolff duct - after the German anatomist Kaspar Friedrich Wolff (1733–1794). The mesonephric was already the duct of the first generation embryonic kidney ( pronephros ) of amniotes , and is taken from the second kidney condition, the primitive kidney.

In both sexes, the urinary tract emerges from a bulge ( ureteral bud ) of the urinary tract near its mouth in the urogenital sinus .

Male sexual differentiation

The normal male sexual differentiation of the main duct of the testis, arising in the context of the mesonephric duct vas deferens (vas deferens), the seminal vesicles , as well as through the prostate withdrawing ejaculatory duct as end portion of the ductus deferens. The uppermost part - the section of the urinary duct located cranially (towards the skull) - becomes an appendage of the epididymis, the appendix epididymidis . The epididymis , which also emerges from the urinary duct , also contains parts of the urinary tract .

Like the bulbourethral glands, the prostate is a descendant of the urogenital sinus .

Female sexual differentiation

A. Before the embryonic differentiation, the gonads and the reproduction channel ( Wolff gear = blue and Mullerian gear = red ) as a result of the gene products of the Y chromosome , is carried out a differentiation to testis by means of the Anti-Mullerian Hormone , English Anti- Müllerian hormone (AMH) initiate the involution of the [[Müller-Gang <Müllerian Ganges]]. The development of Wolff's Ganges progresses through testosterone production. C. In the absence of testicular determinative factor , English testis determining factor (TDF) develop the ovaries and the Wolff transition degenerate, while the derivatives of the Müllerian duct unfold itself.

In the context of female sexual differentiation, the urinary duct disappears completely, apart from a few remains. Sometimes a small area of ​​the lower section can be left, which can become a Gartner cyst in the vaginal wall .

The cesspool and the Wolffian duct of vertebrate development. A: early embryonic stage, shows the cloaca which takes up the contents of the urinary bladder and the rectum and connects to Wolff's duct. These conditions are found in lower vertebrates B: later stage, shows the beginning of differentiation into a ventral urogenital sinus , which takes up the contents of the urinary bladder and Wolff's duct and the dorsal part which depicts the rectum. C: in the further course, the cloaca, the urogental sinus and the rectum differentiate; the ureter separates from Wolff's duct. D: Complete differentiation.

Developmental disorders

In the context of what is known as complete androgen resistance (testicular feminization), fetal androgens can not develop their effect due to a genetic defect in the androgen receptor. Since the Wolff gang needs androgens (testosterone) to maintain it, it regresses spontaneously under these conditions. Since the Müller ducts (necessary for female gender differentiation) also recede under the influence of the anti-Müllerian hormone, there is no development of the internal sex organs (uterus and vagina or epididymis and Semen ducts).

Individual evidence

  1. ↑ Libbie Henrietta Hyman : A laboratory manual for comparative vertebrate anatomy. 1922 (1920s)
  2. ↑ C. Dadak (ed.): Sexuality, reproduction, pregnancy, birth . 3. Edition. Facultas Verlag, Vienna 2010, ISBN 978-3-7089-0613-3 , p. 54 .