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Stages of Digestion

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Stages of Digestion
Digestion
Unit 11
Nutrition
Kevin Browne
Stages of Digestion
Four Stages of Digestion
•
•
•
•
Ingesting
Digesting
Absorbing
Eliminating
Stage 1:Ingesting
• The starting point of
the digestion process.
Stage 2: Digesting
• Mouth: Mechanical and Chemical digestion begins.
• Mechanical digestion is the chewing and breaking food
down into smaller pieces
• Each small piece of food is a bolus
• Saliva lubricates the food, and contains an enzyme, called
amylase.
• Chemical digestion occurs when amylase begins to break
down complex carbohydrates.
• Esophagus: as food passes
through the pharynx, the
epiglottis covers the airway
tube.
• The food moves on to the
esophagus.
• The esophagus is a tube
that connects the pharynx
and the stomach.
• The esophagus is
long and muscular
• The bolus is pushed
through the
esophagus in a
process called
peristalsis.
Absorbing:
Stomach
• Your stomach is like a
stretchable muscular bag.
• Inside the stomach is
gastric juice, which is very
acidic.
• The stomach walls are lined
with mucus, that protects
the tissue.
• Pepsin is an enzyme which
breaks down protein, and
needs an acidic
environment.
• The bolus breaks down into
a liquid called chyme.
Small Intestine
• Once the chyme leaves
the stomach, it empties
into the small intestine.
• The first metre is called
the duodenum.
Digestion is complete
after foods leaves.
• Within the first 30 cm
are ducts that connect
to other organs.
• Pancreas: produces
enzymes
• Liver: produces bile.
The Large Intestine or Colon
• The large intestine is the final
part of the digestive tract and
is about 1.5 metres long. Any
food not already digested
makes it here. However, there
is normally not much in the way
•
of nutrients left at this point in the
system.
Soluble fibre is partly absorbed
here, and any water left over from
the whole process is re-absorbed
here as well. Once water is
removed, the waste product
becomes harder and forms
faeces.
Eliminating: The Rectum
• Anything reaching the
rectum should be purely
waste, because the
digestive system is very
efficient at removing
nutrients.
• From here, faeces are
passed into the anus for
expulsion from the body.
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