From www.corecharity.org.uk/The-Hazards-of-Swallowing-Glass.html
The human digestive tract has the capacity to cope with a very wide variety of food and drink as part of the normal diet. Man has evolved as an omnivore and has adapted to a mixed diet from a variety of sources. Bones in meat and fish are usually removed but may be swallowed, usually without hazard. Foods from plants may include tough, fibrous and spiky parts which are not eaten deliberately but can pass through the intestine without problem. Most of these non-nutrient components of the diet can be digested to some extent making them less hazardous.
Materials like glass, plastic and metal are not changed in their passage through the bowel and might, in theory at least, be more hazardous than natural substances. Occasionally children or people in disturbed mental states swallow these sorts of things deliberately and it is remarkable how rarely they develop problems.
The risks of swallowing these materials depends on their size, shape and sharpness. Small pieces can travel right through the bowel and be passed normally without problems. The bigger the person, the larger the piece that can go through. In general, narrow objects pass through the bowel more easily and smooth ones are less likely to get caught.
Sharp objects such as glass fragments might be expected to cause damage but rarely do so because of the gentle way in which the bowel handles them. Small splinters or spikes could cause perforation but this is very unusual. A small perforation rarely leads to peritonitis and usually heals quickly with any leakage contained. Small fragments may also cause a little bleeding into the bowel which can be detected on tests in the stools but serious blood loss is very rare. Ground glass, despite its reputation in thrillers, has no serious effect on the bowel.
The mouth, particularly the tongue, is very adept at detecting anything of different texture in food or drink. Children and adults will spit out something that does not feel right. Babies and the elderly may not be so discriminating which could put them at greater risk. Once food has been swallowed it passes quickly down the oesophagus (gullet) into the stomach. The narrowest point of the gastrointestinal tract is the exit from the stomach, called the pylorus. Objects which are too large to pass through will therefore stay in the stomach. They can often be retrieved using a flexible instrument called an endoscope which is passed down through the mouth. Anything which passes through the pylorus is unlikely to cause further problems.
Anyone who believes that he or she may have swallowed glass should contact their doctor or the local Accident and Emergency Department. Glass, especially small fragments of the sort of glass that is used in bottling, is not seen easily on X-ray. Treatment is usually conservative, that is 'wait and see', unless there is any indication of an unusual complication.
Read more: What happens if you swallow bits of broken glass?. | Answerbag
http://www.answerbag.com/q_view/71281#ixzz0vm1GdBzF
