Your digestive tract is one of your body’s most vital systems—it takes your food on an amazing journey once your lunch leaves your lips. First, it travels down the esophagus to the stomach, where acids start breaking it down so your body can use it. After a few hours of digestion, your food then moves through the small intestine, where most of its nutrients are absorbed. After that, it carries on to the large intestine, finally making its grand exit. Although it’s a complicated process, digestion is designed to happen so seamlessly that we rarely notice how busily our bodies are working. Sometimes, however, things go wrong, bringing on uncomfortable abdominal pain. Here are a few reasons why your belly may be aching—from simple to serious: