Which segment of the nephron is primarily responsible for the reabsorption of the majority of filtered water and solutes?
Solution
Correct Answer: Option B
The proximal convoluted tubule (PCT) is the segment of the nephron primarily responsible for the reabsorption of the majority of filtered water and solutes. This is because the PCT has a highly specialized epithelial lining with numerous microvilli, increasing its surface area to maximize reabsorption. Approximately 65-70% of the filtered sodium and water is reabsorbed here, along with a large proportion of other solutes such as glucose, amino acids, and bicarbonate.
In contrast:
- The distal convoluted tubule mainly fine-tunes sodium, potassium, and calcium reabsorption but does not reabsorb the majority of filtered substances.
- The thick ascending limb of the loop of Henle is impermeable to water and plays a critical role in the active reabsorption of sodium, potassium, and chloride but not water.
- The collecting duct fine-tunes water reabsorption in response to antidiuretic hormone (ADH) but handles only a smaller fraction of filtered water compared to the PCT.
Thus, the proximal convoluted tubule is the primary site where the bulk of reabsorption occurs, making it essential for maintaining fluid and electrolyte balance.
Reference: Guyton and Hall Textbook of Medical Physiology, 14th Edition, Chapter 26: Urine Formation
In contrast:
- The distal convoluted tubule mainly fine-tunes sodium, potassium, and calcium reabsorption but does not reabsorb the majority of filtered substances.
- The thick ascending limb of the loop of Henle is impermeable to water and plays a critical role in the active reabsorption of sodium, potassium, and chloride but not water.
- The collecting duct fine-tunes water reabsorption in response to antidiuretic hormone (ADH) but handles only a smaller fraction of filtered water compared to the PCT.
Thus, the proximal convoluted tubule is the primary site where the bulk of reabsorption occurs, making it essential for maintaining fluid and electrolyte balance.
Reference: Guyton and Hall Textbook of Medical Physiology, 14th Edition, Chapter 26: Urine Formation
Practice More Questions on Our App!
Download our app for free and access thousands of MCQ questions with detailed solutions