Which type of nephron is involved in urine concentration?

The Henle’s loop and vasa recta play a significant role in production of concentrated urine. Nephrons with long loops of Henle like the Juxta medullar nephrons help in this process. Cortical nephrons have short loops of Henle . Vasa recta is absent or highly reduced for such nephrons. So, their contribution to concentration of urine is nil.