When a person is experiencing heartburn, he or she feels a burning sensation in the throat and midchest. think about the structures of the digestive system. what most likely causes the burning sensation? the muscle at the end of the esophagus is not able to close, which allows stomach acid and digested food to go back up into the esophagus. the villi in the small intestine are producing extra acid that is then concentrated at the pharynx. the esophagus goes into muscle spasms while the salivary glands produce excess acid. too much water absorption in the large intestine disrupts the ph of the digestive system, causing acid to reenter the stomach.