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A stoma (plural stomata, from Greek στόμα "mouth") is an opening, either natural or surgically created, which connects a portion of the body cavity to the outside environment. Surgical procedures in which stomata are created are ended in the suffix -ostomy and begin with a prefix denoting the organ or area being operated on.
In anatomy, a natural stoma is any opening in the body, such as the mouth. Any hollow organ can be manipulated into an artificial stoma as necessary. This includes the esophagus, stomach, duodenum, ileum, colon, pleural cavity, ureters, urinary bladder, and kidney pelvis.
One well-known form of an artificial stoma is a colostomy, which is a surgically created opening in the large intestine that allows the removal of feces out of the body, bypassing the rectum, to drain into a pouch or other collection device. The historical practice of trepanation was also a type of stoma.
Stomata are found in particular in procedures involving the gastrointestinal tract (GIT) or gastrointestinal system (GIS). The GIT begins at the mouth or oral cavity and continues until its termination, which is the anus. This surgical procedure is invoked usually as a result of and solution to disease in the GIT. The procedure involves bisecting this tube, usually between the later stage of the small intestine (ileum) and the large intestine or colon, hence colostomy, and exiting it from the body in the abdominal region.
The point of exiting is what is known as the stoma. For greatest success and to minimize negative effects, it is preferable to perform this procedure as low down in the tract as possible, as this allows the maximal amount of natural digestion to occur before eliminating fecal matter from the body. The stoma is usually covered with a removable pouching system (adhesive or mechanical) that collects and contains the output for later disposal. Modern pouching systems enable most individuals to resume normal activities and lifestyles after surgery, often with no outward physical evidence of the stoma or its pouching system.
Examples of stomata 
- Gastrostomy (also see percutaneous endoscopic gastrostomy)
- Urostomy (also see Ileal conduit urinary diversion)