vomiting

Forcible ejection of the stomach contents from the mouth, usually following nausea.

Causes include illness, motion sickness, certain drugs, inner ear disorders, and head injury. Vomiting may occur without nausea (e.g., after extreme exertion). Two centres in the brain's medulla oblongata are believed to control it; the vomiting centre initiates and controls a series of muscle contractions beginning at the small intestine and moving through the stomach and esophagus. This reaction may be set off by the chemoreceptor trigger zone, stimulated by many toxins and drugs, to rid the body of them, or by stimuli from various parts of the body that may be stressed or diseased. Severe vomiting may cause dehydration, malnutrition, or esophageal wall rupture. Vomiting of blood may be a sign of bleeding ulcer or other upper digestive tract disorders. See also bulimia.

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▪ pathology

also called  emesis  

      the forcible ejection of stomach contents from the mouth. Like nausea, vomiting may have a wide range of causes, including motion sickness, the use of certain drugs, intestinal obstruction, disease or disorder of the inner ear, injury to the head, and appendicitis. It may even occur without nausea, such as after extreme physical exertion.

      Vomiting is believed to be controlled by two distinct brain centres—the vomiting centre and the chemoreceptor trigger zone—both located in the medulla oblongata. The vomiting centre initiates and controls the act of emesis, which involves a series of contractions of the smooth muscles lining the digestive tract. These contractions begin at the small intestine and move successively through the stomach and the esophagus until the stomach contents are forced out the mouth. The vomiting centre responds directly to stimuli from various parts of the body that may be stressed or diseased. The chemoreceptor trigger zone, by contrast, is stimulated by many toxins and drugs. Activation of this brain region stimulates the vomiting centre, which initiates emesis in an effort to rid the body of the toxin. In severe cases vomiting may result in dehydration, malnutrition, or rupturing of the esophageal wall. Treatment is directed toward the cause of the vomiting. It is important to drink plenty of clear fluids so that further dehydration does not occur.

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