Download File - King`s General Science

• Before the body can make use of the food
you eat, the food has to be broken down to
release the nutrients (digested).
• The nutrients are then absorbed into the
bloodstream and taken to the cells where
they can be used.
• Four Digestion processes
– Ingestion
– Digestion
– Absorption
– Egestion
Not All food needs digesting!
Simple sugars, water, vitamins &
minerals are small molecules and can
be absorbed as they are
– they do not need to be digested!
Where & HOW does absorption take
place…?
Food group
Mechanical
-Teeth /
stomach…
Specific
enzymes do
their bit…
End product
& absorbed
where… ?
Main regions of the
alimentary canal and
associated organs
Mechanical
Digestion?
Chemical
Digestion?
Digestion
• Is the breaking-up of food into small
soluble pieces.
• Food in the stomach is mixed up and stored
(turned into a soup-like liquid)
• Stomach cells make enzymes (Pepsin) and
hydrochloric acid are released to aid digestion
• This acid also kills bacteria present in food.
Stomach – bag with lots of muscle in its walls…
Food held ~ 1-4 hours, liquids ~ a few minutes
• Food is then slowly released
into the small intestine (gut)
where most of the digestion
happens.
• First part – Duodenum
Where pancreas & bile fluids
added joins
Small intestine ~ 6 meters long
In the duodenum (enzymes ~ amylase, trypsin,
lipase) from the pancreas are added and bile
which is made in the liver is also added.
The bile helps to neutralize the acid from the
stomach and also helps to break the fat into
little droplets.
Gall bladder
stores bile
Absorption: the movement of
digested food molecules through the
wall of the intestine into the blood
Absorption
• Is when food nutrients pass through the gut wall and into the
blood stream.
• The lining of the small intestine is folded and has little fingerlike projections called villi which increase the area for
absorption.
•The surface is only one cell thick
which speeds up the absorption of
nutrients.
•Cells covering the villi make
enzymes eg Lactase (breaks down
lactose in milk)
Discussion:
• What is the small intestine for?
• Why are there villi on the inner
surface of the small intestine?
By this stage most carbs – broken to simple sugars, proteins
to amino acids and fats to fatty acids & glycerol
Blood from the digestive system
must first filter through the liver
before it travels anywhere else in
the body.
The principal roles of the liver
include removing toxins from the
body, processing food nutrients
and helping to regulate body
metabolism (how your body gets
its energy). Also produces bile…
• In the Large Intestine (colon &
Rectum), water and any
remaining minerals are
absorbed
• What is left consists of
remnants of fibre, other
undigested material and
bacteria.
Egestion
• The remains are formed into solid wastes (faeces / poo)
and stored in rectum.
• They are removed from the body through the anus.