What is the X in X-mas?
1932, from German nephron (1924), from Greek nephros "kidney," from PIE *negwhro- "kidney" (cf. Latin nefrones, Old Norse nyra, Dutch nier, German Niere "kidney").
nephron neph·ron (něf'rŏn)
The functional unit of the kidney, consisting of the renal corpuscle, the proximal and distal convoluted tubules, and the nephronic loop.
The functional unit of the kidney, in which waste products are filtered from the blood and urine is produced. The nephron consists of a system of tubules in close association with a network of blood vessels. As fluid that is filtered through the glomerulus of the nephron enters the tubules, its composition is gradually changed by the absorption and secretion of solutes, and it eventually leaves the nephron as urine. See more at Bowman's capsule, glomerulus, loop of Henle.