Family Doctor Books
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Published in association with the British Medical
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Family
Doctor Books |
Preview of Understanding Indigestion & Ulcers
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Many people sometimes have only a vague
idea of the size, shape, position and function of the stomach and other
digestive organs. This section of the book gives a brief outline of the
normal process of digestion and what each of the main parts of the digestive
system does. If this is all familiar to you, just skip this account and
move straight on to pages 5–8, where the main types of indigestion
are described.
To extract nutrients from the food we eat we need
to digest it. First the food has to be changed into a liquid or semi-liquid
form. Then, complex substances such as fats and proteins have to be
broken down into smaller chemical units that can be absorbed through
the walls of the intestine into the bloodstream. The process of digestion
begins in your mouth, where the teeth and tongue chop large pieces
of food into smaller ones.The salivary glands release saliva into the
mouth to mix with the food. Saliva makes it easier to move food round
your mouth to chew it and it also contains an enzyme called salivary
amylase which starts to digest carbohydrates such as sugars and starches.
It is slightly acid and, when you’re not actually eating, it goes
on being produced and helps to keep your mouth and teeth clean and
stop plaque developing on your teeth. People who have conditions in
which salivary production is reduced often experience a dry mouth,
difficulty swallowing and increased tooth decay.
Once the food is chewed and softened in the mouth,
the tongue pushes it to the back of the throat, where muscles propel
it down the oesophagus (or gullet). The food passes from the oesophagus
into the stomach through a muscular one-way valve, the lower oesophageal
sphincter, which prevents the contents of the stomach from being forced
back into the chest when the stomach contracts or when you lie flat.
The stomach has three main functions, shown in the
box. Eventually the liquidised food is pushed onwards through another
valve, the pylorus, into the duodenum, the first few inches of the small
intestine. Here further chemicals are added to neutralise the stomach
acid, together with enzymes from the pancreas to help digest carbohydrates,
fats and proteins, and bile from the liver to help digest fats. The digested
food then passes into the remaining 20 feet (six metres) of small intestine,
so called because, although it is long, its diameter is smaller than
that of the large intestine. The chemical breakdown is completed in the
small intestine and the chemical constituents of the meal are absorbed
into the blood and lymphatic vessels.
The main tasks of the large intestine are to reabsorb
the water that is used in digestion and to eliminate the undigested food
and fibre.
Major
abdominal organs. |
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The mouth. |
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What can go wrong?
Almost everyone experiences occasional attacks of indigestion
which are usually quite brief. We may feel blown out or distended after
a large meal, and get some relief when we bring up wind. Most of the
wind that we bring up is a result of swallowing air as we eat, but some
is produced by a chemical reaction in the stomach or from carbonated,
fizzy drinks. The solutions are to eat less, eat more slowly and go easy
with fizzy drinks. You may have discovered for yourself that certain
foods
– fried onions, for example – give you an uncomfortable sensation
in the upper abdomen which lasts for only an hour or so. Again the answer
is obvious: don’t eat it.
More persistent indigestion is usually linked with
the acid produced by the stomach. If the valve at the lower end of the
oesophagus becomes weak or defective, the acid juices in the stomach
may be pushed back upwards into the oesophagus causing a burning sensation
(heartburn). This is often troublesome at night, when you lie flat. The
underlying condition is called gastro-oesophageal reflux and is described
in more detail.
Stomach acid may also cause problems if it attacks
the lining of the stomach itself – peptic ulcer disease, described
in detai. Our understanding of peptic ulcer disease has changed greatly
in recent years, thanks to the discovery of an infective agent called
Helicobacter pylori.
The third common cause of indigestion, called non-ulcer
dyspep-sia, is something of a puzzle. This is the diagnosis given to
people who have persistent symptoms of indigestion but in whom the tests
for gastro-oesophageal reflux and stomach ulcers are normal. Dyspepsia
is actually just the medical name for indigestion. Some people with this
type of indigestion are eventually found to have a disorder affecting
another part of the digestive system, such as gallstones or the irritable
bowel syndrome. In others, the pain is found to be caused by some disorder
of the lower ribs and muscles of the abdominal wall. Most people with
non-ulcer dyspepsia, however, seem to have sensitive stomachs which cause
symptoms at times of emotional stress. The condition is described in
greater detail.
Very occasionally, indigestion may be the first symptom
of a more serious condition such as stomach cancer. Stomach cancer is
becoming less common than in the past and it occurs much less frequently
than peptic ulcer disease or gastro-oesophageal reflux. It is described
in greater detail.
FUNCTION OF THE STOMACH
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- It acts as a storage container, so that we can swallow all
the food needed for many hours within a few minutes.
- It plays a large part in the physical and chemical processes
of digestion. Food in the stomach is churned and crushed, although
you notice this only when the activity is excessive because your
stomach does not contain the same number of sensory nerves as
other parts of the body, such as the skin. Glands within the
stomach lining produce a powerful acid and enzymes that help
break down the constituents of food into simpler chemical compounds.
The walls of the stomach are normally protected against acid
attack by a layer of protective mucus, but, if this is reduced
or damaged, it may lead to ulcer formation. The oesophagus doesn’t
have this protective lining and so is more easily damaged by
acid.
- Food may stay in the stomach for several hours, during which
time the acid will destroy most of the bacteria and other micro-organisms
that may have contaminated it. Very little is absorbed directly
into the bloodstream through the stomach walls, apart from a
few substances such as alcohol and aspirin.
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KEY POINTS
- During normal digestion, food is broken down so
that it can be absorbed into the body
- The stomach produces acid and pepsin to help in
this process
- If the lining of the stomach is weakened, or if
acid production is altered, then indigestion can occur
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