Download The digestion process

The digestion process
© Food – a fact of life 2009
Foundation
Learning objectives
• To understand food is used as a fuel by the body.
• To recognise the body parts involved in digestion.
• To know the roles of different body parts in
digestion.
• To understand the four major phases of digestion.
© Food – a fact of life 2009
Food as a fuel
The body requires energy from food.
Our bodies act as a converter, releasing energy and
nutrients from food.
Sometimes food can take 2 or 3 days to be fully
digested and absorbed by the body.
© Food – a fact of life 2009
Do you know the body parts involved in the digestion
process?
© Food – a fact of life 2009
Organs of the digestion process
Mouth
Stomach
Anus
© Food – a fact of life 2009
Oesophagus
Small intestine
Colon
Mouth
The teeth mechanically break food down into smaller
pieces.
Different shaped teeth tear, chop and grind the food.
The cheeks and tongue help to push the food towards
the teeth.
The food is then rolled into a ball and swallowed down
the oesophagus.
© Food – a fact of life 2009
Saliva
Saliva will be released into the mouth at the sight,
smell, taste or even the thought of food.
Saliva is secreted from glands at the back of the
mouth and under the tongue.
An enzyme found in saliva helps breaks down starch
into simple sugars.
Saliva also moistens the food making it easier to chew
and swallow.
© Food – a fact of life 2009
Oesophagus
When food is swallowed, the muscles in the
oesophagus contract and relax, helping to push the
food down into your stomach.
After the food has been swallowed, it is carried down
the oesophagus towards the stomach.
Each mouthful of food takes about six seconds to
reach the stomach once it is swallowed.
Even, when the body is upside down the food will still
pass from the mouth to the stomach.
© Food – a fact of life 2009
Stomach
The stomach is a sack made of muscles that contract
and churn food, breaking it down even further.
The acid and enzymes found in the stomach also help
to break down the food.
Food can spend up to 2 to 3 hours in the stomach.
When the food has been churned into a creamy
mixture known as chyme, it passes gradually into the
small intestine.
© Food – a fact of life 2009
Small intestine
The small intestine is a tube about 6 metres long.
The inner surface of the small intestine is folded into tiny
finger-like structures called villi.
The surface area of the villi is about 30m2. This is
equivalent to the size of a tennis court.
The first section of the small intestine is called the
duodenum.
© Food – a fact of life 2009
Duodenum
In the duodenum, food is diluted with pancreatic
enzymes and bile, which decrease stomach acidity.
The contents continue to travel through the lower small
intestine, becoming more liquid as they mix with water,
mucus, bile, and pancreatic enzymes.
© Food – a fact of life 2009
Pancreas and the gall bladder
A duct entering the duodenum provide digestive
juices to help digestion.
From the pancreas:
- sodium bicarbonate to neutralise acid from the
stomach;
- digestive enzymes.
From the gall bladder:
- bile salts to help breakdown the fat.
© Food – a fact of life 2009
Absorption
After the chyme has passed into the duodenum some
of the nutrients can pass through the wall of the villi
and into the bloodstream.
These nutrients can be used by body cells, for energy
and growth.
Insoluble, undigested food moves on inside the small
intestine.
Ultimately, the small intestine absorbs most of the
nutrients. All but about 1 litre of fluid remains before the
chyme moves into the large intestine through
peristalsis.
© Food – a fact of life 2009
Peristalsis
These are the waves of muscular contractions which
move food along the digestive system.
Circular muscles in the wall relax in front of the food
whilst circular muscles behind the food contract,
pushing the food onward from the oesophagus
through to the large intestine or colon.
© Food – a fact of life 2009
Colon
The colon is shorter than the small intestine.
The main function of the colon is to remove water.
Bacteria ferment the remaining food and produce
molecules and gases.
The final product formed is faeces, which are is stored
in the rectum until these are excreted.
© Food – a fact of life 2009
Phases of digestion
Ingestion - food taken into the mouth.
Digestion - physical and chemical processes that start
in the mouth, and continue in the stomach and small
intestine.
Absorption – nutrients moving across the gastrointestinal lining, into the blood.
Elimination – undigested food such as dietary fibre is
excreted as faeces.
© Food – a fact of life 2009
Review of the learning objectives
• To recognise the body parts used in digestion.
• To understand food is used as a fuel for the body.
• To know the roles of different body parts in
digestion.
• To understand the four major phases of digestion.
© Food – a fact of life 2009
For more information visit
www.foodafactoflife.org.uk
© Food – a fact of life 2009