Final answer:
The secondarily important site of tubular reabsorption in the kidneys is the distal convoluted tubule, where approximately 10-15% of filtered water is reabsorbed.
Step-by-step explanation:
The question relates to the various parts of the nephron responsible for tubular reabsorption in the kidneys. While the proximal convoluted tubule (PCT) is the primary site for reabsorption, the secondary importance for tubular reabsorption points to the Loop of Henle, the distal convoluted tubule (DCT), and the collecting ducts. Considering the options given, the correct answer is the distal convoluted tubule.
In the DCT, approximately 10-15 percent of filtered water is reabsorbed before the forming urine enters the collecting ducts, making it the secondarily important site of tubular reabsorption. This process is regulated by aldosterone, which increases Na+/K+ ATPase in the basal membrane of the DCT. As a result, Na+ is reabsorbed, and this promotes the movement of Cl- out of the lumen into the interstitial space.