Download Animals, including humans: The digestive system

Animals, including humans: The digestive system
Objectives

Describe the simple functions of the basic parts of the digestive system in humans
Plenary
Pupils should recognise that food goes through their bodies and emerges as poo. How might
this happen? Pupils should come up with creative ideas about how a ‘Poo-matic Machine’
might turn food into poo. Some pupils may recognise that food needs to be pulped and have
things added (acid).
The parts of the digestive system
Give the pupils unlabelled diagrams of the human digestive system. Which parts can they
name? They should know the mouth, tongue and teeth and may identify the lower parts of the
system as the ‘stomach’, ‘guts’ or ‘bowels’ (the stomach is a specific part of the system while
‘guts’ and ‘bowels’ are general terms for the intestines). Ask the pupils to label the mouth,
tongue and teeth.
What do people use their mouth, tongue and teeth for? They chew food and add saliva,
turning it into a pulp (bolus) so it can be swallowed. What would happen if we didn’t have
teeth, tongue and mouth?
Identify the oesophagus and ask pupils to label it on their diagrams. It has the mouth at one
end and the stomach at the other, so what may its function be? Pupils may suggest that food
travels through it. Explain that it is muscular and moves food to the stomach by squeezing it
(this action is called peristalsis).
The next part that the food reaches is the stomach. Pupils should, with guidance, label the
stomach. The stomach is full of acid, which breaks down the food. Ask a volunteer to taste
some unsweetened lemon juice and explain that your stomach acid (gastric acid) is even
stronger than that.
Next come the ‘guts’ or the intestines. Point at the intestines and ask which the large
intestine is and which the small intestine is. The large intestine is the thicker one and the
small intestine is the thinner one (although the small intestine is 4x longer). Pupils should
label these.
Food travels first through the small intestine; this helps break down the food so nutrients can
be extracted. Food then stays in the large intestine for about 20 hours, where the rest of the
water and nutrients are extracted and the food turns into poo, which leaves the body through
the anus.
To revise what they have just learnt, pupils should draw arrows on their diagram to show how
food travels through the different parts of the digestive system.
© Education Umbrella 2015
Pupils must note:
The digestive system is made up of the mouth, tongue, teeth, oesophagus, stomach, small
intestine and large intestine.
Pupils may note:
Food moves down the oesophagus and into the stomach, where it is broken down by acid.
Nutrients are extracted in the intestines and the remains leave the body through the anus.
Are there any similarities between their real digestive system and their Poo-matic Machine
designs?
Journey through the digestive system
Pupils should write a short story about a slice of cheesecake and its adventure through the
human digestive system. The story should mention the mouth, oesophagus, stomach and both
intestines. They may mention the cheesecake zooming down the oesophagus, being dissolved
in acid or meeting other types of food during its journey.
Possible extra-curricular questions
Why is poo brown?
Poo is brown due to bile being added while the food is in the intestines. Adding bile results in
a substance called stercobilin, which makes the poo brown.
Why do we get sweetcorn in our poo?
Our bodies do not produce the right substances to break down the yellow shell of a piece of
sweetcorn. Therefore, it passes through our digestive systems unaffected. You can measure
how long food stayed in your body by eating sweetcorn and timing out long it takes for it to
be pooed out.
Why does poo smell?
When food passes through our intestines, it is broken down with the help of bacteria. The
bacteria produce materials and gas containing sulphur and methane, which causes our poo
and farts to smell.
© Education Umbrella 2015