The digestive system breaks down food into nutrients that cells can use. As food moves through the mouth, esophagus, stomach, small intestine and large intestine, physical and chemical digestion converts it into simple molecules that enter the bloodstream. The blood transports these nutrients to cells throughout the body. Cells produce waste as a byproduct, which the blood carries to the kidneys. The kidneys filter wastes out of the blood to produce urine, which is stored in the bladder.

1. Living Systems Focus Question: How do cells get the food they need? Investigation 1-2