How Urine Production is Controlled
Your body's got an incredibly clever system for controlling exactly how much urine you produce, and it all starts in your brain. The hypothalamus constantly monitors your blood's water levels as it flows through your head.
When your blood becomes too concentrated (you're getting dehydrated), your pituitary gland releases more ADH anti−diuretichormone. This hormone travels through your bloodstream to your kidneys, where it makes the collecting ducts more permeable to water.
The result? Your kidney tubules reabsorb more water back into your blood, producing less concentrated urine. When you're well-hydrated, less ADH is released, so more water gets filtered out as dilute urine.
Each nephron contains a Bowman's capsule, glomerulus (a ball of capillaries), and the Loop of Henle that dips down into the medulla. Blood enters under high pressure from the renal artery, and this pressure forces small molecules like water, glucose, salts and urea through the capillary walls - a process called ultrafiltration.
Remember: This whole process is a negative feedback loop - your body automatically adjusts to maintain perfect water balance without you having to think about it!