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Digestive and Excretory System
Overview
• By Rebecca K. Fraker
Digestive System
The Mouth: The Trip Starts Here
• The trip starts here!
• The teeth cut pieces of food
into smaller portions.
• Saliva shoots in and begins
digestion.
Down the Hatch
• For a proper start, chew food
until it is ground small and
mixed with the saliva.
• Then swallow!
Salivary glands
esophagus
Food is pushed
down this pipe
into the stomach
stomach
The food is squashed by
muscular contractions and
acid is added.
Proteins start to be digested by
enzymes
Duodenum
Small intestine
Large intestine
Rectum
Anus
In the duodenum digestive juices from the pancreas
are added and bile which is made in the liver is also
added.
The enzymes help to break the food into smaller
particles.
Gall bladder
stores bile
The bile helps to neutralize the acid from the
stomach and also helps to break the fat into
little droplets.
Stores
Bile
Trace the path of the food.
Notice that after the food goes
into the duodenum,
it goes into the small intestine,
circles around and
THEN takes a loop in the large
intestine.
Small Intestine
And Enzymes at
Work
In the small intestine the enzymes help to break the
food up into smaller particles.
Proteins ----- amino acids
Carbohydrates ------ glucose
Fats ---- fatty acids and glycerol
• The tiny particles are
then absorbed into the
blood stream.
• The particles diffuse
into the blood and are
carried all round the
body.
In the large intestine the water that is needed is taken
back into the blood. Food is now all digested.
The solid waste or feces is stored in this part of the large
intestine or rectum before passing out the body through
the anus.
Anus – the solid waste passes out of the body through
this special muscular part.
The waste, called feces, can show what a person (or
other organism) has eaten.
SUMMARY
• Food is chewed to make digestion easier.
• The mouth starts to digest the food and the stomach
makes it into a liquid.
• The small intestine finishes digesting the food and
the tiny dissolved food particles move into the
blood.
• Undigested food passes out through the large
intestine.