Final answer:
The kidneys filter the blood to produce urine, excreting approximately 1-2 liters per day based on the glomerular filtration rate (GFR), with men having slightly higher GFR than women. Most of the filtrate is reabsorbed, and only a fraction is eliminated as urine, necessary to remove metabolic wastes.
Step-by-step explanation:
The amount of fluid from the kidney that actually leaves the body as urine is approximately 1-2 liters per day. This is based on an average glomerular filtration rate (GFR) which produces about 180 L/day of filtrate in men and 150 L/day in women, with 99% of this filtrate reabsorbed, leading to a relatively small volume of urine excreted. The kidneys play a crucial role in this process by filtering the blood and producing urine.
While men typically have a GFR that produces about 125 mL/min of filtrate, women have a slightly lower average production at 105 mL/min. The kidneys reabsorb most of the water from the filtrate, preserving body's fluid balance. Only a fraction (approximately 0.8%) of this filtrate is excreted as urine. The minimal urine output necessary to remove metabolic waste and maintain proper bodily functions is around 0.47 liters per day.