2. Physical and Chemical Digestion
• Digestion is: the process by which nutrients are broken down into
simple molecules that can be absorbed into the bloodstream.
• There are two types of digestion Physical and chemical
• Physical digestion :
• No new substance is formed
• Chewing, melting, mixing churning
• Chemical digestion:
• New substances are formed
• Enzymes (biological catalysts) are needed to control the reactions.
• Example starch is change into sugar in the mouth with the help of the
enzyme salivary amylase.
• Proteins are changed into amino acids
• Fats are changed into fatty acids and glycerol
• Carbohydrates are changed into simple sugars like glucose
3. Digestive system/ alimentary
canal
• MOUTH
• food chewed and melted
• mixed with saliva
• starch changed to maltose
by amylase in saliva.
• OESOPHAGUS
• Tube (25cm) from mouth to
stomach
• Muscle contract and relax
to push food down
(peristalsis)
4. Digestive system
• STOMACH
• pouched shape bag with walls
made of muscle
• top left of abdomen under
diaphragm
• lining makes gastric juice which
contains HCl and enzymes
pepsin & rennin
• Food is churned into chyme
• fat melts
• HCl kills bacteria
• Enzymes change protein into
peptides
5. • SMALL INTESTINE
• joins stomach to large intestine
• 6m long, coiled up in centre of
abdomen.
• Food moves by peristalsis.
• Bile made in liver and stored in gall
bladder flows into intestine and
emulsifies fat.
• Pancreatic juice made in pancreas
flows into the intestine contains
enzymes that change peptides into
amino acids, and starch into sugar.
• Intestinal juice is made by the
intestine wall. It contains enzymes
that finish of the digestion of protein,
fat and carbohydrate.
Digestive
system
6. Absorption • Absorption is the passing of
digested food into the
bloodstream.
• Happens mainly in the small
intestine.
• The inside of the small
intestine is covered with tiny
hairlike projections called
villi.
• The villi give a large surface
area through which food can
be absorbed.
• The blood carries the digested
food to every body cell where
it is used for energy & growth
7. The Large
Intestine
• 2m long , also called the bowel or
colon.
• Joins the small intestine to the
anus.
• It passes up the right side of the
abdomen, across under the stomach
and down the left side.
• The start is called the caecum and
the last few cms. are called the
rectum
• Functions: 1. completes absorption,
2. absorbs water, 3. makes Vits B &
K, 4. eliminates waste.
• This solid waste is called faeces
• A high fibre diet is important for
the health of the large intestine
