Final answer:
The collecting ducts in the kidney merge in the renal medulla to empty urine into the renal papillae, then through the calyces to the renal pelvis and down the ureters to the bladder. ADH regulates water reabsorption in the collecting ducts to concentrate the urine.
Step-by-step explanation:
The student's question pertains to the anatomy of the kidney and the process of urine collection and excretion. Specifically, the process begins with numerous collecting ducts converging in the renal medulla and emptying the filtrate which has now become urine into the renal papillae located at the tip of the renal pyramids. From there, urine drains into the minor calyces, then to the major calyces, eventually moving into the renal pelvis. This pelvis functions as a funnel to channel the urine down into the ureters, which leads to the urinary bladder. It is essential to note that collecting ducts receive an aqueous fluid (filtrate) from nephrons and as they descend deeper into the medulla, they merge to form terminal ducts that empty urine at a papilla.
In response to antidiuretic hormone (ADH), the collecting ducts become more permeable to water, facilitating the reabsorption of water into the bloodstream, making the urine more concentrated as it progresses through the renal system.