The Vomiting Reflex – Gastrointestinal System Example

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"The Vomiting Reflex" is a good example of a paper on the gastrointestinal system. Vomiting is a reflex behavior characterized by forceful convulsive expulsion of gastric contents through the mouth (Haskell, 1924; Berne et al. , 2004). This reflex is controlled by a specific area in the medulla oblongata called the vomiting center, which receives afferent inputs from various receptors in the body (Berne et al. , 2004). The figure below summarizes the physiology of vomiting. Receptors that provide afferent inputs to the vomiting center are found in the intestinal tract, throat, and higher brain centers (Guyton and Hall, 2006).

For instance, distention of the stomach and duodenum or touching the back of the throat stimulates receptors that send signals to the vomiting center, resulting in a cascade of events that lead to nausea and vomiting (Berne et al. , 2004). It must be noted, however, that when the vomiting reflex is triggered, the same series of events take place regardless of the stimulus that activates the vomiting center. The characteristics of the vomitus or the material that is being expelled through the mouth can aid in determining what the gastrointestinal pathology is and where along the intestinal tract the lesion is located.

Since the vomitus originates from within the intestinal tract itself, its integrity tells a lot about what is happening inside the gut. For instance, vomitus consisting of blood probably indicates an upper GI tract bleeding such as but not limited to esophageal varices, Malory-Wiess disease, and gastric ulcers (Kliegman et al. , 2007; Fauci et al. , 2008). If the blood appears to be bright red and fresh, it usually indicates active bleeding. On the other hand, coffee-ground vomitus generally indicates old blood.

Newborns who present with excessive salivation and vomiting of milk right after being fed may have esophageal atresia, pyloric atresia, or antral stenosis (Kliegman et al. , 2007). In addition, the characteristics of the vomitus also provide clues as to where the lesion might be. One good characteristic that is often used in localizing GI lesions is to determine if the vomitus is billions in nature (Kimura and Leoning-Baucke, 2000). Non-bilious vomitus indicates an obstruction above the Ampulla of Vater (from the first part of the duodenum upwards) (Greenberger et al. , 2009).

Meanwhile, bilious vomitus indicates an obstruction below the Ampulla (in the 2nd and 3rd parts of the duodenum) such as in the case of duodenal atresia (Kimura and Leoning-Baucke, 2000; Greenberger et al. , 2009). However, it must be noted that the value of vomitus character as a diagnostic tool is very limited if used solely. It must be combined with the other presenting signs and symptoms of the patient to accurately diagnose GI diseases.

References

Berne, R., Levy, M., Koeppen, B., and Stanton, B. 2004. Physiology. 5th ed. Elsevier Inc., Philadelphia, Pennsylvania. pp 557-558

Fauci, A., Kasper, D., Longo, D., Braunwald, E., Hauser, S., Jameson, J., and Loscalzo, J. 2008. Harrison’s Principles of Internal Medicine. 17th edition. The McGraw-Hill Companies. United States. Ch. 286

Greenberger, N., Blumberg, R., and Burakoff, R. 2009. Current diagnosis and treatment in Gastroenterology, Hepatology, and Endoscopy. The McGraw-Hill Companies, Inc. United States. p79

Guyton, A., and Hall, J. 2006. Textbook of Medical Physiology. 11th edition. Elsevier Inc., Philadelphia, Pennsylvania. pp 823-824

Haskell, R. 1924. The physiology of vomiting. J Natl Med Assoc. 16(1): 8–10.

Kimura, K., and Leoning-Baucke, V. 2000. Bilious Vomiting in the Newborn: Rapid Diagnosis of Intestinal Obstruction. Am Fam Physician. 2000 May 1;61(9):2791-2798.

Kliegman, R., Behrman, R., Jenson, H., and Stanton, B. 2007. Nelson Textbook of Pediatrics, 18th ed. Saunders Elsevier. 1600 John F. Kennedy Blvd. Philadelphia Ch 303.

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