The distal part of the loop of Henle that is impermeable to water and actively pumps sodium out of the filtrate to generate the hypertonic interstitium that drives countercurrent exchange; it consists of an initial very thin segment lined by simple squamous epithelium followed by a distal thick segment lined by simple cuboidal epithelium[MP]. [ MP:0011342 ]

Synonyms: loop of Henle ascending limb ascending limb of Henle's loop

This is just here as a test because I lose it