Physiology of Vomiting


With Election 2006 Returns only hours away, I thought it appropriate to provide our readers with some medical information which may come in handy. I found the following article fascinating. The link at the end of the article takes you to a web page called: Stomach Disorders Nausea and Vomiting Health Channel. I was very disappointed that it’s only a web page and not a television channel I can get on Comcast (Damn it!)

“At least after death you're not nauseous.” (Woody Allen in Sleeper)

Vomiting is the forceful expulsion of contents of the stomach and often, the proximal small intestine. It is a manifestation of a large number of conditions, many of which are not primary disorders of the gastrointestinal tract. Regardless of cause, vomiting can have serious consequences, including acid-base derangments, volume and electrolyte depletion, malnutrition and aspiration pneumonia.

The Act of Vomiting

Vomiting is usually experienced as the finale in a series of three events, which everyone reading this has experienced:

1. Nausea is an unpleasant and difficult to describe psychic experience in humans and probably animals. Physiologically, nausea is typically associated with decreased gastric motility and increased tone in the small intestine. Additionally, there is often reverse peristalsis in the proximal small intestine.

2. Retching ("dry heaves") refers to spasmodic respiratory movements conducted with a closed glottis. While this is occurring, the antrum of the stomach contracts and the fundus and cardia relax. Studies with cats have shown that during retching there is repeated herniation of the abdominal esophagus and cardia into the thoracic cavity due to the negative pressure engendered by inspiratory efforts with a closed glottis.

3. Emesis or vomition is when gastric and often small intestinal contents are propelled up to and out of the mouth. It results from a highly coordinated series of events that could be described as the following series of steps (don't practice these in public):

A deep breath is taken, the glottis is closed and the larynx is raised to open the upper esophageal sphincter. Also, the soft palate is elevated to close off the posterior nares. The diaphragm is contracted sharply downward to create negative pressure in the thorax, which facilitates opening of the esophagus and distal esophageal sphincter. Simultaneously with downward movement of the diaphragm, the muscles of the abdominal walls are vigorously contracted, squeezing the stomach and thus elevating intragastric pressure. With the pylorus closed and the esophagus relatively open, the route of exit is clear.

The series of events described seems to be typical for humans and many animals, but is not inevitable. Vomition occasionally occurs abruptly and in the absense of premonitory signs - this situation is often referred to as projectile vomiting. A common cause of projectile vomiting is gastric outlet obstruction, often a result of the ingestion of foreign bodies.

Causes and Consequences of Vomiting

The myriad causes of vomiting are left as an exercise - come up with a list based on personal experience and your understanding of the control of vomition. An important point, however, is that many cases of vomiting are due to diseases outside of the gastrointestinal tract.
Simple vomiting rarely causes problems, but on occasion, can lead to such serious consequences as aspiration pneumonia. Additionally, severe or repetitive vomition results in disturbances in acid-base balance, dehydration and electrolyte depletion. In such cases, the goal is to rapidly establish a definitive diagnosis of the underlying disease so that specific therapy can be instituted. This is often not easy and in many cases, it is advantageous to administer antiemetic drugs in order to suppress vomition and reduce its sequelae.

Here’s the great link: Stomach Disorders Nausea and Vomiting Health Channel

MANY HAPPY RETURNS!!!!!