Final answer:
The renal tubule functions in reabsorption of water and essential nutrients and secretion of waste products. Glomerular filtration is separate and occurs in the renal corpuscle, while the production of urine is a result of the entire renal process, including the collecting ducts.
Step-by-step explanation:
The function of the renal tubule in the kidney is primarily for the reabsorption of water and essential nutrients and the secretion of waste products, not filtration of blood or production of urine directly. The process of glomerular filtration occurs in the renal corpuscle. Then, as the filtrate passes throughout the renal tubules, there occurs the tubular reabsorption mainly in the proximal convoluted tubule and the loop of Henle, where useful substances like salts, water, glucose, and amino acids are reclaimed into the blood in the peritubular capillaries. Additional solutes and wastes that were not reabsorbed, and some substances actively transported from the blood into the tubules, are part of tubular secretion, occurring mostly in the distal tubule. The tubing then collects the resulting filtrate, which becomes urine.