Vomiting is the active expulsion of food from the stomach. Not all food that leaves the mouth has been vomited however, because sometimes it is returned without ever reaching the stomach. See dysphagia, pharyngeal retching, and regurgitation. Immediately prior to vomiting the animal feels nauseous, then there is reflex closure of the epiglottis over the trachea to prevent aspiration of food into the lungs. Finally there is synchronised contraction of the abdominal and diaphragmatic muscles and this increased intra-abdominal pressure ejects the food out of the stomach, up the oesophagus and out of the mouth.