Certified Nephrology Nurse Certification (CNN) Practice Exam

The primary function of the renal tubules is reabsorption of water, ions, and nutrients. After the initial filtration process occurs in the glomeruli of the kidneys, the renal tubules play a critical role in processing the filtrate. The tubular system consists of several segments, including the proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct.

As filtrate passes through these segments, the renal tubules selectively reabsorb essential substances such as glucose, amino acids, electrolytes (sodium, potassium, chloride), and significant amounts of water back into the bloodstream. This process is vital for maintaining fluid and electrolyte balance, ensuring that necessary nutrients are conserved while waste products and excess substances are left to be excreted as urine.

In addition, while the renal tubules contribute to urine production through the processes of reabsorption and secretion, their primary purpose revolves around the recovery of key substances and the regulation of body homeostasis. Secretion of hormones is mainly attributed to different parts of the kidneys, particularly the juxtaglomerular apparatus and not primarily to the renal tubules.