The production of filtrate is carefully regulated so the volume remains the same (mls/hour) despite changes in blood pressure and level of hydration.

Question

The production of filtrate is carefully regulated so the volume remains the same (mls/hour) despite changes in blood pressure and level of hydration. How then, does the body regulate the volume of urine produced? For example, how can urine output diminish when we are dehydrated?

sorry the question couldn't fit. i need help with this question please?

Answer 1

This question is speaking to the key point of how kidneys function. Remember that the filtrate is fluid and dissolved substance that are removed from the bloodstream and enter the system of tubules in the kidney. What happens in the tubule system?

The answer to that is what the kidney is all about. Think of the kidney as a recycling plant. Picture a conveyor belt running through the plant. The filtrate is represented by the items on the belt. The tubule epithelial cells in the kidney are like the workers in the factory - as an item goes by the workers can choose to take the item off of the belt (i.e. recycle it). Or they can choose to let it stay on the belt which eventually carries the item out of the factory to be thrown out as waste.

Letting an item leave the factory is equivalent to secreting a substance in the urine. Taking an item off the belt is like tubular absorption. The "instructions" for the factory workers are constantly changing depending on the needs of the body at any given time. The body's need for water, potassium, sodium, and many other substances is always in flux. The kidneys function by retaining substances we don't have enough of and allowing substances we have too much of to leave.

If the body is dehydrated, the kidney can resorb water from the filtrate and return it to the circulation which prevents it from leaving the body in the form of urine.