Final answer:
The assertion is false; while the kidneys filter blood and reabsorb a significant amount of water to form urine, other forms of water loss through sweating, breathing, and other processes can cumulatively exceed the amount expelled as urine.
Step-by-step explanation:
The statement that the amount of water removed by the kidney as urine is greater than all other sources of water loss combined is false. The kidneys do play a crucial role in water recovery and waste removal, but water is also lost through other means such as sweating, breathing, and evaporation from the skin.
While the entire volume of the blood is filtered through the kidneys about 300 times per day, and 99 percent of the water filtered is recovered, the rest of the water loss is significant, including through feces, sweat, and exhalation.
The kidneys filter blood plasma and reabsorb a significant amount of water. About 82 percent of the water is recovered as the filtrate travels through the nephron, mainly before it reaches the collecting ducts.
The collecting ducts are mainly responsible for fine-tuning the concentration of the urine, which can lead to more or less water being reabsorbed based on the body's needs, as regulated by hormones such as ADH. It's worth noting that the collecting ducts regulate the final 10 percent of water reabsorption.