Vomiting Definition and Information

The forceful expulsion of contents from the stomach, also called emesis. The force of vomiting may also draw digestive material from the duodenum (first section of the small intestine). Like sneezing and coughing, vomiting is a protective and reflexive mechanism to rid the body of substances that threaten its well-being.

Vomiting occurs in response to nerve impulses from the brain’s emesis center (also called vomiting center). The emesis center receives input from numerous body systems, including the gastrointestinal tract, vestibular system (which regulates balance), and circulatory system, as well as from the chemoreceptor trigger zone, another region of the brain that receives signals from the body. Pain signals, particularly those the vagus nerve conveys, also travel to the emesis center, which is why severe pain may result in nausea (queasiness and the feeling of being about to vomit) and vomiting.

Other variables that influence the emesis center include sensory perceptions such as foul smells or disturbing sights (which activate the chemoreceptor zone), hormonal shifts (such as occur in pregnancy to cause morning sickness), and signals from the gastrointestinal tract indicating chemical changes such as from the presence of infection or inflammation. Nausea, the sensation of queasiness and the urge to vomit, typically though not always precedes vomiting.

A complex series of physiologic events takes place to permit vomiting. Simultaneously the epiglottis closes (blocking the airway), the larynx lifts, and the upper esophageal sphincter opens. Then the diaphragm violently contracts, pulling it down and causing the open the lower esophageal sphincter to open, while the abdominal muscles contract with comparable force to push gastric (stomach) contents upward through the now open esophagus. Vomitus is highly acidic; chronic vomiting such as occurs with anorexia nervosa causes erosion of the tooth enamel. This material has a bitter taste and often leaves a burning sensation in the upper throat. Though the mechanism of vomiting is involuntary, there is some voluntary control over its initiation.

Episodic vomiting generally has no lasting consequences, though the very young and the very old can quickly become dehydrated. Vomiting that continues longer than three or four weeks without apparent cause requires medical evaluation. Treatment may include antiemetic medications, dietary changes, or therapies to resolve underlying conditions. Complications of chronic or repeated vomiting may include esophagitis, electrolyte imbalance, and aspiration pneumonia.


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