vasa recta

noun plural

vasa rec·​ta -ˈrek-tə 

1

: numerous small vessels that arise from the terminal branches of arteries supplying the intestine, encircle the intestine, and divide into more branches between its layers

2

: hairpin-shaped vessels that arise from the arteriole leading away from a renal glomerulus, descend into the renal pyramids, reunite as they ascend, and play a role in the concentration of urine