Final answer:
The process of selectively transporting molecules from the peritubular fluid to the lumen of the renal tubules is known as tubular secretion. This process, which is one of the steps in urine formation, is essential for maintaining the body's chemical balance by removing additional wastes and substances from the blood into the renal tubule for excretion.
Step-by-step explanation:
The process whereby molecules are selectively transported from the peritubular fluid to the lumen of the renal tubules is called tubular secretion. This process involves the transfer of molecules like excess ions, waste products, and drugs out of the blood and into the urine, helping to maintain the body's chemical balance.
Tubular secretion is a critical stage in urine formation. It is one of the steps following glomerular filtration, and it is distinct from tubular reabsorption, which moves substances from the filtrate back into the bloodstream. During secretion, cells lining the renal tubules actively transport materials from the blood in the surrounding peritubular capillary network into the renal tubule fluid. This process allows for the removal of substances that were not initially filtered out in the glomerulus, such as certain organic acids and bases. Secretion primarily occurs in the proximal convoluted tubule, the loop of Henle, and the distal convoluted tubule. This contributes to the excretory capacity of the nephron, allowing the body to eliminate wastes and maintain the internal environment's chemical and electrolyte balance.
In short, tubular secretion works in conjunction with glomerular filtration and tubular reabsorption to form urine, which is then excreted from the body.