What is the primary function of the collecting duct?

What is the primary function of the collecting duct?

• A. Reabsorbs water and ions to finalize concentration
• B. Filters blood
• C. Secretes urine
• D. Produces erythropoietin

Answer: (A)

The collecting duct’s main job is final water reabsorption to concentrate urine, under the control of antidiuretic hormone. When ADH is present, aquaporin channels in the principal cells allow water to move out of the tubule into the surrounding tissue, darkening and concentrating the urine. It also reabsorbs some sodium to fine-tune volume, but the defining function is producing the concentrated urine through water reabsorption. Filtration of blood happens in the glomerulus, not the collecting duct. Erythropoietin is produced by kidney interstitial cells, not by the collecting duct. The collecting duct isn’t where urine is formed or secreted at its source; its role is the final adjustment of urine concentration.

The collecting duct’s main job is final water reabsorption to concentrate urine, under the control of antidiuretic hormone. When ADH is present, aquaporin channels in the principal cells allow water to move out of the tubule into the surrounding tissue, darkening and concentrating the urine. It also reabsorbs some sodium to fine-tune volume, but the defining function is producing the concentrated urine through water reabsorption.

Filtration of blood happens in the glomerulus, not the collecting duct. Erythropoietin is produced by kidney interstitial cells, not by the collecting duct. The collecting duct isn’t where urine is formed or secreted at its source; its role is the final adjustment of urine concentration.