Journey of a piece of bread through the digestive system

Describes the journey of a piece of bread through the body.

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  • Created by: Amy49
  • Created on: 14-11-11 20:06
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First the bread enters the mouth (ingestion). It is
chewed and ground by teeth which cut the bread
into smaller pieces that have a larger surface area
allowing enzymes to digest the bread quicker. Also
in the mouth, amylase enzymes begin the digestion
of starch which is found in bread. The amylase
enzymes are found in saliva (made in the salivary
glands) which helps to moisten the bread. The
bread is then easy to swallow and the tongue
pushes small pieces of bread to the back of the
throat and into the oesophagus.
The chewed bread is then pushed along the oesophagus by
muscles, in a process called peristalsis, to the stomach
where the digestion of protein begins.
Pepsin, an enzyme found in the stomach will start to digest
the protein in the bread and the acidic conditions of the
stomach will kill any bacteria in the bread. The bread is
held in the stomach for several hours so the digestion
of protein begins. The semi-digested food is then released
into the first part of the small intestine called the
In the duodenum, more enzymes are added to the bread; lipase, amylase, maltase, peptidase and
trypsin. SEE DIAGRAM. All these enzymes are made by the pancreas. Another substance called bile
(made in the liver and stored in the gall bladder) is also added, its purpose being to emulsify any
lipase. This increases the bread's surface area making it easier for lipase enzymes to digest it. A
further purpose of bile and pancreatic juices is to neutralise the bread. After being in the acidic
stomach, the bread needs to be neutralised before going any further in the digestive system.
The bread will continue through the duodenum. Throughout
this process the bread is changed into a thin, watery, soluble
mixture which is ready to be dissolved.
Then the soluble products of digestion (glucose, amino acids,
glycerol and fatty acids) are absorbed through the walls of the
ileum. The ileum is adapted to have a large surface area so it
can absorb as much as possible. It is long, it has folds in it and
has many villi (tiny projections from the lining); home to
microvilli. All of these factors ensure the soluble substances can
be absorbed quickly and efficiently. The substances are
absorbed into the bloodstream.

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What's left of the bread is mainly fibre (cellulose), water, bacteria and cells lost from the lining of the
gut. It goes into the large intestine where water is removed. This forms a more solid material called
Faeces are stored in the rectum and are eventually pushed out the anus. They are egested.…read more

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