Renal Tubules

(1) In some invertebrates, that part of the excretory organs, or nephridia, consisting of coiled tubules. (2) In vertebrates (including man), the renal tubules constitute a large part of the nephrons of the pronephroi, the mesonephros, and the metanephros. When ciliated funnels are present (in some adult Selachii and amphibians), the renal tubules open into the coelom. When there are no funnels (in the postembryonic period of all other vertebrates), they terminate blindly. At the opposite end, the renal tubules empty into the ureters through the collecting tubules.