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Vomiting (or emesis) is the forceful expulsion through the mouth of the contents of one's stomach. It is a mechanism for expelling ingested illness-causing food poisons. The act may be triggered by stimuli which might indicate the possibility of poisoning, such as motion sickness, or sight of decayed food, or other people vomiting. It can also be induced with an emetic or prevented with an antiemetic. Nausea also may occur after surgery due to the chemicals employed, see Postoperative nausea and vomiting. Vomiting sometimes also occurs in response to an emotional trauma, or after a concussion; in the latter case it can indicate that the head injury is moderate or severe and requires immediate medical attention.
The act may also be triggered intentionally by stimulating the constrictor muscle located in the back of the throat with a finger or other object. It may be triggered voluntarily due to a psychological disorder such as anorexia nervosa or bulimia or to remove a poison in case such has been ingested. (Note: Some poisons should not be vomited as they may be more toxic when inhaled. Always contact a Poison Control center before inducing vomiting.)
The feeling that one is about to vomit is called nausea.
On airplanes and boats, special bags are supplied for sick passengers to vomit into. Alternatively, a special disposable bag is available containing absorbent material that solidifies the vomit quickly, making it convenient and safe to keep (leakproof, puncture resistant, odorless) until there is an opportunity to dispose of it conveniently.
1 Reflex
Vomiting is co-ordinated in the vomiting center in the medulla. Receptors on the floor of the fourth ventricle of the brain represent a chemoreceptor trigger zone, stimulation of which can lead to vomiting. The chemoreceptor zone lies outside the blood-brain barrier, and can therefore be stimulated by blood-borne drugs which can stimulate vomiting, or inhibit it.
The vomiting act encompassess:
- Increased salivation to protect the enamelTooth enamel is the smooth top layer of a tooth which protects the underlying dentine, with its many nerves, from injury and decay. Tooth enamel is denser and chemically more inert than other body tissues, but can be attacked and destroyed by lengthy expo of teeth from stomach acids.
- Retroperistalsis , starting from the middle of the small intestineIn biology the small intestine is the part of the gastrointestinal tract between the stomach and the large intestine. In humans over 5 years old it is about 7m long. It is divided into three structural parts: duodenum, jejunum and ileum . Food from the st, sweeping up the contents of the digestive tract into the stomach, through the relaxed pyloric sphincter.
- A lowering of intrathoracic pressure (by inspiration against a closed glottisThe space between the vocal cords is called the glottis . As the vocal cords vibrate, the resulting vibration produces a "buzzing" quality to the speech, called voice or voicing . Sounds production involving only the glottis is called glottal''. English h), coupled with an increase in abdominal pressure as the abdominal musclesThe abdomen (from the Latin word meaning "belly") is the part of the body between the pelvis and the thorax. The front of the abdomen is the abdominal cavity, which is separated from the thoracic cavity by the diaphragm. The lining of the abdomen is calle contract, propels stomach contents into the esophagusThe esophagus oe/oesophagus , or gullet is the muscular tube in vertebrates through which ingested food passes from the mouth area to the stomach. Food is passed through the esophagus by using the process of peristalsis. Specifically, in mammals, it conne without involvement of retroperistalsis. The lower esophageal sphincter relaxes.
- Vomiting is ordinarily preceded by retching. The purpose of retching is to build up the pressure needed to expel the stomach contents from the body. In retching, the body makes movements similar to vomiting. These spasms build up pressure within the chest cavity. When a sufficient amount of pressure has been created, the diaphragm transfers the pressure from the chest to the abdomen, and this pressure then results in actual vomiting.
