The document describes the digestive and respiratory systems. The digestive system breaks down food into nutrients and energy through a multi-step process involving the mouth, esophagus, stomach, small intestine, large intestine, liver, gallbladder and pancreas. The respiratory system inhales oxygen and exhales carbon dioxide through the nose, mouth, larynx, windpipe, bronchial tubes and lungs. Air enters the lungs where thousands of alveoli allow oxygen to pass into the blood and carbon dioxide to leave the body.