(or '''emesis''') is the forceful expulsion of the contents of one's
Stomach through the mouth. Although it has probably evolved as a mechanism for expelling ingested
Poison s, '''vomiting''' may result from many causes not related to poisoning, ranging from
Gastritis to
Brain Tumor s, or elevated intracranial pressure (ICP). The feeling that one is about to vomit is called
Nausea . It usually precedes vomiting, but it does not always lead to vomiting.
Antiemetic s are sometimes necessary to suppress nausea and vomiting, and in severe cases where
Dehydration develops,
Intravenous fluid may need to be adminstered.
The medical branch investigating vomiting, emetics and antiemetics is called .
is co-ordinated in the vomiting center in the lateral medullary reticular formation 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 that can
Stimulate Vomiting , or
Inhibit It .
There are various sources of input to the vomiting center:
- Increased Saliva tion to protect the Enamel of Teeth from stomach acids (excessive vomiting does lead to Caries ). This is part of the PNS output.
- Retroperistalsis , starting from the middle of the Small Intestine , 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 Glottis ), coupled with an increase in abdominal pressure as the Abdominal Muscles contract, propels stomach contents into the Esophagus without involvement of retroperistalsis. The Lower Esophageal Sphincter relaxes. This is part of the motor output, and it is also important to note that the stomach itself does not contract in the process of vomiting.
- Vomiting is ordinarily preceded by retching.
- Vomiting also initiates a SNS response causing both sweating and increased heart rate.
The
Neurotransmitter s that regulate vomiting are poorly understood, but inhibitors of
Dopamine ,
Histamine and
Serotonin are all used to suppress vomiting, suggesting that these play a role in the initiation or maintenance of a vomiting cycle.
Vasopressin and
Neurokinin may also participate.
As the stomach secretes acid, vomit contains a high concentration of
Hydronium Ion s and is thus strongly
Acidic . The potential physiological complications associated with excessive vomiting are mainly
Metabolic Alkalosis (increased blood
PH ),
Hypokalemia (
Potassium depletion) and
Hypochloremia (
Chlorine depletion). The hypokalemia is an indirect result of the
Kidney compensating for the loss of acid.
The content of the ''vomitus'' (vomit) may be of medical interest. Fresh
Blood in the vomit is termed
Hematemesis ("blood vomiting"). Old blood bears resemblance to coffee grounds (as the
Iron in the blood is
Oxidized ), and when this matter is identified the term "coffee ground vomiting" is used.
Bile can enter the vomit during subsequent heaves due to
Duodenal contraction if the vomiting is severe.
Fecal Vomiting is often a consequence of
Intestinal Obstruction , and is treated as a warning sign of this potentially serious problem ("signum mali ominis"); such vomiting is sometimes called "miserere".
If the vomiting reflex continues for an extended period of time with no appreciable vomitus, the condition is known as or '''dry heaves''', which can become painful and debilitating.
Vomiting may be due to a large number of causes, and protracted vomiting has a long
Differential Diagnosis .
Causes in the
Digestive Tract :
Causes in the
Sensory System :
Causes in the brain:
Metabolic disturbances (these may irritate both the stomach and the parts of the brain that coordinate vomiting):
Opioid s, many
Chemotherapy drugs and a host of other drugs may cause nausea and vomiting.
An ''emetic'', such as
Syrup Of Ipecac , is a substance that induces vomiting when administered orally or by injection. An emetic is used medically where a substance (typically
Poison ) has been ingested and must be expelled from the body immediately. Inducing vomiting can remove the substance before it is absorbed into the body.
An
Antiemetic is a
Drug that is effective against vomiting and
Nausea . Antiemetics are typically used to treat
Motion Sickness and the
Side Effect s of some
Opioid Analgesic s and
Chemotherapy directed against
Cancer .
It is quite common that when one person vomits, others nearby will become nauseated, particularly when smelling the vomit of others, often to the point of vomiting themselves. It is believed that this is an
Evolved trait among
Primates . Many primates in the wild will tend to browse for food in small groups. Should one member of the party react adversely to some ingested food it may be advantageous (in a survival sense) for other members of the party also to vomit. This tendency in human populations has been observed at drinking parties, where excessive consumption of
Alcohol ic beverages may result in a number of party members vomiting nearly simultaneously, this being triggered by the initial vomiting of a single member of the party. This is even found in the computer game
Theme Hospital , where it is referred to as a 'vomit wave' and can spread through the hospital quickly.
There have also been documented cases of a single ill and vomiting individual inadvertently causing others to do so, when they are especially fearful of also becoming ill, through a form of
Mass Hysteria .
Most people try to contain their vomit by vomiting into a sink, toilet, or trash can, as both the act and the vomit itself are widely considered embarrassing. 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.
People who vomit chronically (e.g. as part of an
Eating Disorder such as
Bulimia Nervosa ) may devise various ways to hide this abnormality.
As with other physiological processes involving body wastes, vomiting has )
- Whale s vomit regularly (every 7 to 10 days) as a means of the ordinary digestive process, to expel inedible things they have swallowed.
- The domestic Proverbs 26:11 "As a dog returneth to his vomit, so a fool returneth to his folly."
- Owl s will expel the undigestible bones and fur of their meals after partial digestion of the nutritious parts rather than passing them through the digestive tract.
- Some adult Bird s regurgitate food to feed their young, triggered by a Feather or a Beak of their young. The food can be either incompletely digested or partially predigested, depending on the species. Some bird species may also use regurgitation as a form of defense, vomiting when wounded or molested. When an intruder or a Predator comes near a Fulmar on its nest, the bird vomits oil up to 3 Feet at the enemy. Larger animals, such as Wolves , may also regurgitate partially or undigested food to feed their young.
- When in danger, the Sea Cucumber may eject its entire digestive tract. The animal is able to re-grow another one.
- Some large mammals, including horses, cannot or rarely vomit.
- Many rodents are readily killed by commercial poisons because they lack the ability to vomit, which can be problematic for some pet owners.
Vomiting is known by several other names, generally considered
Slang . Commonly used ones are: "hurling", "puking", "throwing up", "upchucking", "boking", "talking to God on the big white telephone", "ralphing", "making an offering to the porcelain god", "blowing chunks", "barfing", and "spewing".
