Video narration
How can a nephron make urine without losing what your body still needs? Think of a coffee filter-but a nephron is a tiny processing system, not a simple strainer. Follow blood. It enters the glomerulus, where pressure pushes water and small dissolved substances into the nephron. Blood cells and most proteins stay in the bloodstream. Now the tubule sorts what was filtered. Useful water, glucose, and salts move back into the blood. This selective recovery is called reabsorption. Unwanted material stays in the forming urine, while some additional wastes are added from the blood. The later tubule sections adjust the balance of water and salts. Then the collecting duct fine-tunes the water content, and the remaining fluid leaves as urine. So how does the nephron do it? It filters first, then carefully reclaims what you need and adds wastes-not by straining everything out.