Where within the nephron does the majority of tubular reabsorption occur?

• A. Distal convoluted tubule
• B. Collecting duct
• C. Loop of Henle
• D. Proximal convoluted tubule

Answer: (D)

Verified step by step guidance

1. Understand the function of the nephron: The nephron is the functional unit of the kidney, responsible for filtering blood and forming urine. It consists of several parts, each with specific roles in the process of urine formation.
2. Identify the role of the proximal convoluted tubule (PCT): The PCT is the first segment of the nephron tubule and is primarily responsible for the reabsorption of water, ions, and nutrients from the filtrate back into the bloodstream.
3. Compare the reabsorption capacity of different nephron segments: The PCT reabsorbs approximately 65-70% of the filtered water and sodium, along with a significant amount of glucose, amino acids, and other ions, making it the site of the majority of tubular reabsorption.
4. Consider the functions of other nephron segments: The distal convoluted tubule and collecting duct are involved in further reabsorption and secretion, but to a lesser extent compared to the PCT. The loop of Henle primarily concentrates urine by reabsorbing water and salts.
5. Conclude that the proximal convoluted tubule is the correct answer: Based on its role and capacity for reabsorption, the PCT is the segment where the majority of tubular reabsorption occurs within the nephron.