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    Home » Science Experiments for Kids » Digestive System Model

    Digestive System Model

    October 26, 2019 By Emma Vanstone Leave a Comment

    The digestive system is made up of several organs working together, to make an organ system ( Digestive system ). This activity shows how to make an easy digestion system model using food and tights!

    This activity can also be found in my new book Gross Science!

    Images of gross science experiments taken from the book Gross science

    What is Digestion?

    Digestion is the process by which large insoluble molecules of food are broken down into smaller soluble molecules which can be used by the body.

    Digestion starts in the mouth where food is broken into smaller pieces as people chew. Food is mixed with saliva which contains an enzyme called amylase. Amylase starts to break down carbohydrates in the food.

    Human Digestive System Diagram

    Food then passes down the oesophagus and into the stomach. The stomach contains stomach acid and more enzymes which break up the food further. Stomach acid is actually hydrochloric acid which kills most harmful bacteria and provides the optimum pH for enzymes to get to work.

    As food is slowly released from the stomach into the small intestine the liver adds alkaline bile to the mixture. This neutralises the stomach acid so as not to harm the small intestine and helps to break up fats.

    The pancreas makes three digestive enzymes which are also added into the food mixture. These are:

    Protease for digesting proteins.

    Carbohydrase for digesting carbohydrates

    Lipase for digesting lipids.

    The small intestine produces even more enzymes to continue digesting proteins, carbohydrates and fats. Nutrients are absorbed through the walls of the small intestine and transported to cells in the body by blood.

    In the large intestine water is absorbed from food, and undigested food is passed to the rectum as faeces.

    The final part of the journey is when the faeces pass out of the anus hopefully into a toilet!

    Nutrients from the food we eat are absorbed by the small intestine and then the large intestine absorbs water and any nutrients not absorbed by the small intestine.

    Undigested food becomes faeces or poo which are excreted from the body via the rectum and anus!

    Human digestive system. Anatomical vector illustration in flat style isolated over white background.

    Easy digestive system model with tights

    You can make a very simple digestion model using one leg of a pair of tights as the small intestine.

    What you need to make a digestive system model

    Potato masher – or something else to crush the food with.

    Bowl

    Funnel

    1 small banana or piece of bread

    1 plain biscuit

    Yoghurt- optional

    Jar or bowl

    30ml water

    30ml orange juice

    Green and red food colouring – optional

    Medium size ziploc bag – stomach

    Scissors

    I leg from a pair of tights  – small intestine

    Tray or plate

    Digestion Model - materials - tights container, banana, digestive biscuit

    Digestion Model Instructions

    Place the biscuit and banana into a bowl and gently crush with a potato masher. This represents the food being chewed. Pour the crushed food into an empty ziploc bag and add the water. The water represents saliva.

    Pour the orange juice into the bag ( this represents stomach acid) Make sure there is no air in the bag and seal it.

    Digestion Model - plastic bag with stomach contents for a digestion experiment

    Squeeze the bag for about a minute crushing up the biscuits and banana further. This represents the food breaking down further inside the stomach.

    Once the stomach contents feel like a thick liquid, cut a small hole in the one corner and carefully squeeze into the open leg of the tights ( small intestine ).

    Digestion Model - girl with a digusted face

    At this point you can add a little red and green food colouring, but this is not necessary. The red food colouring represents dead red blood cells that are being disposed of and the green represents bile which is released by the liver.

    Hold the tights over the tray or a bowl and gently squeeze the liquid out. The liquid on the tray represents the nutrients the body absorbs and uses.

    Keep squeezing until no more liquid comes out. If you used food colouring it might be a good idea to wear gloves for this part.

    Digestion Model squeeze through tights
    Digestion Model – squeeze through tights

    The food left behind in the tights represents waste products that cannot be absorbed.

    Cut a hole in the bottom of the tights and squeeze the contents into the jar. This is the poo!

    Digestion Model - the final stage, push the pretend poo through the tights
    Digestion Model – end result poo

    Digestive System Model Challenge

    Change the food you “digest” and investigate to see of you can make a different colour poo!

    Did you know the stomach walls are made of muscle and mix the food helping break it down?

    The small intestine contains lots of thin structures called villi. These give a very large surface area to absorb food molecules.


    Digestion in a Nutshell

    Food is initially broken down in the mouth as you chew helped by amylase ( an enzyme found in saliva )

    It then passes down the oesophagus into the stomach where it mixes with stomach acid and enzymes.

    The liver makes bile to help break up fats and neutralise the acidic mixture heading to the small intestine from the stomach.

    The pancreas adds more enzymes to the mix.

    Food is broken down further in the small intestine where small usable molecules are absorbed through the small intestine walls into the blood.

    Water is absorbed by the large intestine.

    Waste products are expelled via the anus!

    If you enjoyed this activity we’ve got lots more human body investigations suitable for kids of all ages you might like.

    collage of images taken from a digestion experiment


    Last Updated on January 12, 2022 by Emma Vanstone

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    Safety Notice

    Science Sparks ( Wild Sparks Enterprises Ltd ) are not liable for the actions of activity of any person who uses the information in this resource or in any of the suggested further resources. Science Sparks assume no liability with regard to injuries or damage to property that may occur as a result of using the information and carrying out the practical activities contained in this resource or in any of the suggested further resources.

    These activities are designed to be carried out by children working with a parent, guardian or other appropriate adult. The adult involved is fully responsible for ensuring that the activities are carried out safely.

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