Pharyngula

Animations of urogenital development

I found these on youtube, a couple of nice cartoony animations of the development of the urogenital system. This is one of the weirder modules in organogenesis, I think; many strange things go on that are relics of ancestral states. We actually build three pairs of kidneys—pronephros, mesonephros, and metanephros—and throw each one away in succession, except the last. Both sexes form paramesonephric (or Müllerian) ducts, in blue in the animation, and these form the core of the female plumbing, but again, males basically throw it away and use a more primitive duct (the mesonephric or Wolffian ducts, in green). It’s a bizarre way to construct an organ, but what’s going on is that we have two systems, excretion and reproduction, tied together in ways that constrain the other’s development, and each is building on elements of the other.

It’s in French, but that shouldn’t slow anyone down. It’s easy to figure out what “paramesonephrique” must refer to, for instance.

Males:

Females: