The kidneys are responsible for filtering certain components of blood and producing urine from them. In an adult, the kidneys are typically capable of processing about 1 to $1.5$ liters of water per hour depending on the individual and conditions within the body. In a condition known as water intoxication, a person ingests more water (usually 3 or more liters in a single sitting) in a shorter period of time than the kidneys can process. In a child, the amount of water required to induce water intoxication is much less.  The regulation of water and sodium levels in the nephrons is adjusted in two regions of the kidneys where water and sodium can be reabsorbed from the nephron and returned to circulation. Those regions are the:
A. proximal convoluted tubule and distal convoluted tubule
B. the loop of Henle and the distal convoluted tubule
C. the distal convoluted tubule and the collecting duct
D. the proximal convoluted tubule and the loop of Henle
Choose A, B, C or D as your solution.
The correct answer is $\mathrm{B}$. In the proximal convoluted tubule, the primary events are the reabsorption of nutrients and water. There are two regions in the nephron where large amounts of sodium and water are reabsorbed. In the loop of Henle, the countercurrent multiplier system is used, which leads to the reabsorption of salts (sodium and chloride) and water. In the distal convoluted tubule, the hormone aldosterone influences the reabsorption of salts and water followed by osmosis.