Final answer:
Tubular secretion is the process where the renal tubule extracts chemicals from the blood and adds them to tubular fluid. It works alongside tubular reabsorption to maintain homeostasis of water and solutes in the body. These processes occur sequentially in different parts of the nephron and are regulated by hormones.
Step-by-step explanation:
The process of the renal tubule extracting chemicals from capillary blood and adding them to tubular fluid is known as tubular secretion. This is a critical step in the formation of urine and helps in maintaining the balance of substances in the body. It is the reverse of tubular reabsorption, where substances are reabsorbed from the filtrate back into the blood.
The filtration process starts in the glomerulus, followed by reabsorption of substances like water, sodium, and glucose in the proximal convoluted tubule and loop of Henle. Tubular secretion mainly takes place in the distal convoluted tubule, where additional substances are removed from the blood and added to the tubular fluid.
Tubular reabsorption and secretion in the proximal convoluted tubule (PCT) are crucial for balancing water and solutes in the body. During reabsorption, substances like sodium are actively pumped out of the PCT, with water following passively due to obligatory water reabsorption. Secretion adds additional solutes and wastes into the tubular fluid, with hormones such as ADH influencing water recovery in the collecting ducts based on the body's needs.