Simply put

s very concentrated hydrochloric acid and instead of fingers holding the top closed, there are two sets of muscles at the base of the ribcage, together known as the Lower Oesophageal Sphincter (or LOS).If you tip or squeeze the balloon when it's full, it will leak unless it is held tightly closed. With the stomach, that would mean concentrated acid leaking into the tube above, the oesophagus, which it may attack, and is frequently experienced as heartburn or acid reflux.

The oesophagus is the tube food passes down from the throat, through the chest to the stomach.

At the bottom of the chest, it has to pass through a hole in the diaphragm, breathing muscle, which is one of the main muscles forming the LOS. This hole is called the “Hiatus”.

In many people, some of the stomach pushes up through this hole into the chest – a condition known as a hiatus hernia. When this happens, the muscles do not line up properly so reflux is more likely to occur.Hiatus hernias may develop for many reasons - you can even be born with one, but for most people it is unlikely to cause any problems - apart from perhaps, occasional, mild heartburn which we may treat with an antacid.

Spill concentrated acid on your hand and you'll be scarred for life. The lining of the oesophagus makes mucous to help protect the inner surface but it may not help against a tide of acid reflux and cause scarring and inflammation known as oesophagitis.

Acid will not break down fats and animal tissue so, in the same way as we use detergent to allow water to remove grease from a plate, sometimes some bile is needed to help.

If bile also refluxes into the oesophagus along with the acid, it may start to break down the tissue lining the oesophagus and the body could start to digest itself. For protection, some of the normal cells may be replaced with acid-resistant cells like those found in the intestines.

This is the condition known as Barrett's Oesophagus.

However, these changed cells have the ability in some people to mutate to cancer.

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