the.com/renal cortex

means The outer layer of the kidney, where the nephrons' filtering units (glomeruli) do the actual work of straining waste and excess fluid out of the blood.

from 'Renal' comes from Latin 'renes,' meaning kidneys — the same root that gives us 'renal failure.' 'Cortex' is Latin for 'bark' or 'rind,' the tough outer covering of a tree, borrowed by anatomists for any outer layer of an organ that wraps around a softer interior — the same word used for the brain's cerebral cortex or the adrenal cortex. Put together, it's literally 'kidney bark': the rind of the organ, as opposed to the medulla (Latin for 'marrow' or 'core') underneath.