Burps, Bloating, and Flatulence

The Canadian site C•Health has a nice primer on the basics of gas production. the kind that takes place inside the body.

"Forgive me": the facts about flatulence
If swallowed air doesn't make its way out in the form of a burp, it may migrate from the stomach down into the colon. Here is where a burp can become a fart. Gas in the colon also comes from the natural breakdown of food by bacteria in the colon. The food that is not digested in the stomach and small intestine moves to the large intestine for breakdown; this includes carbohydrates such as undigested fibre from fruits and veggies or lactose after eating dairy products.

And as with a belch, flatulence needs to flee our body. This time it passes through a different sphincter, the anal sphincter, but the concept is the same: Air vibrates as it passes through a tiny, pinched up opening and out comes that familiar whoopee cushion sound of passing gas.

And that odour that most people are afraid of others detecting? That actually comes from the bacteria that break down the food in the colon. This bacteria release small amounts of sulphur-containing gases. Yes, the same "rotten-egg" sulphur of stink bomb fame.

"Time to loosen my belt": the nuts and bolts of the bloat
Bloating isn't something you hear or smell, but you will likely feel it. Bloating is the particular sensation of fullness and swelling caused by gas that builds up in the stomach and intestines. The bloating may cause some abdominal pain or discomfort, especially right after you eat. It can accompany burping or breaking wind or be caused by a medical condition that affects the digestive system. Those with irritable bowel syndrome (IBS) or lactose intolerance may experience frequent bloating.