The Five Senses and Beyond: The Encyclopedia of Perception - Jennifer L. Hellier 2017
Emesis is the medical term for vomiting, the forceful expulsion of the contents of the stomach and upper intestinal tract through the mouth. Nausea, increased sweating, increased heart rate, and increased salivation usually precede emesis. Vomiting is a complex reflex coordinated by a region within the medulla oblongata, a portion of the brainstem. Neural input from receptors around various regions of the body can initiate vomiting (Marieb et al., 2011).
Contraction of the abdominal wall causes the lower esophageal sphincter to relax. In turn, this allows the increasing abdominal pressure to push the contents of the stomach up into the esophagus. This is called retching, commonly termed “dry-heaving.” Vomiting occurs when the pressure inside the thoracic cavity, or chest cavity, is high enough to push the stomach contents up the esophagus to the mouth (Widmaier et al., 2011). Vomiting is also accompanied by strong contractions of the upper intestinal tract, which can push the intestinal contents up into the stomach to be expelled with the contents of the stomach. When this occurs bile from the upper intestinal tract can sometimes be seen, discoloring the vomit a greenish hue.
Causes of Emesis
There are a variety of causes of emesis and their frequency ranges from occasional to prolonged, repetitive events that can lead to detrimental health effects. These can involve many different regions of the body as a response to receptors encountering a stimulus that makes them initiate the vomiting reflex. The following are common initiators of the vomiting reflex:
•Distension of the stomach due to overeating, for example, is tracked by mechanoreceptors that measure the stretching of the stomach. This falls into a category of many gastrointestinal causes. Some others are inflammation of related organs, such as the pancreas and appendix.
•Chemoreceptors in the brain and digestive tract react to certain substances, such as poisons and vomit-stimulating chemicals (called emetics), to initiate vomiting in an effort to expel possibly harmful substances from the body.
•Sensory stimuli such as intense pain, rotating movement of the head that affects the sense equilibrium (motion sickness), or pressure increased in the skull or applied to the back of the throat, initiate the so-called “gag reflex” (Widmaier et al., 2011). There are conditions involving the brain that can stimulate emesis. These include concussions, brain tumors, and even migraines.
•Reactions to food allergens or drugs such as alcohol, opioids, and those used in chemotherapy can cause emesis.
•Diseases or pathogens that cause inflammation of organs related to the gastrointestinal tract as mentioned above can usually cause illnesses, such as the “stomach flu.”
•Pregnancy can also stimulate emesis. The common form of nausea and vomiting is morning sickness, but there is a rare complication related to pregnancy called hyperemesis, which is a more persistent state of nausea, vomiting, and dehydration. This has an unknown cause, but it is speculated that the hormonal changes related to pregnancy are a possible factor in developing this condition (Cole, 2010).
There are many complications that arise from vomiting, usually after prolonged or excessive occurrences. Dehydration and electrolyte imbalance is one of the more common complications. This is the excess loss of water and salts that can produce circulatory and metabolic problems.
Aspiration of vomit occurs when the stomach contents enter the respiratory tract. This can lead to choking and possible asphyxiation (low levels of oxygen due to inability to breathe properly) or infection and inflammation of the lungs and bronchioles (known broadly as bronchopneumonia).
Oral health may be affected due to the high acidity of stomach contents coming into contact with the gums and teeth. Tooth enamel can be broken down over time if vomiting is excessive, which is commonly seen in those with bulimia, a condition in which a person is compelled to vomit regularly due to poor self-body image.
Prevention and Treatment
In the prevention and treatment of vomiting, substances known as anti-emetics are effective against vomiting and nausea. They are often prescribed for those who experience motion sickness, morning sickness, and the vomiting/nausea side effects to chemotherapy drugs as well as opioid general pain relievers.
Eric B. Moore
See also: Bitter Sensation; Nociception; Olfactory System; Pregnancy and Sense of Smell; Taste System
Cole, Laurence A. (2010). Biological functions of hCG and hCG-related molecules. Reproductive Biology and Endocrinology, 8, 102. http://dx.doi.org/10.1186/1477-7827-8-102
Marieb, Elaine N., Patricia B. Wilhelm, & Jon Mallatt. (2011). Human anatomy (6th ed.). San Francisco, CA: Pearson Benjamin Cummings.
Widmaier, Eric P., Hershel Raff, & Kevin T. Strang. (2011). Vander’s Human Physiology: The Mechanisms of Body Function (12th ed.). New York, NY: McGraw-Hill.