Overview: Even though you probably don't choose to spend a lot of time thinking about it, your pee is kind of a big deal. Today we're talking about the anatomy of your urinary system, and how your kidneys filter metabolic waste and balance salt and water concentrations in the blood. We'll cover how nephrons use glomerular filtration, tubular reabsorption, and tubular secretion to reabsorb water and nutrients back into the blood, and make urine with the leftovers.