Final answer:
The collecting ducts play a major role in regulating the amount of water reabsorption in the kidney, allowing the production of either a concentrated or dilute urine. This regulation is influenced by the hormone ADH.
Step-by-step explanation:
The role of collecting ducts is to regulate the amount of water reabsorption in the kidney, which determines whether the urine produced is concentrated or dilute. When the blood becomes hyperosmotic, the collecting ducts recover more water to dilute the blood. Conversely, when the blood becomes hyposmotic, the collecting ducts recover less water, leading to concentration of the blood.
This regulation is influenced by the hormone ADH (antidiuretic hormone or vasopressin), which is produced by the posterior pituitary. ADH is secreted in response to changes in plasma osmolarity. When plasma osmolarity rises, more water is reabsorbed and urine volume decreases. When plasma osmolarity decreases, less water is reabsorbed and urine volume increases.