Digestion
Every day we eat meals and drink water, but where does it all go? Your body is an incredible biological machine designed to break down food into fuel. Let us take a journey down the dark, twisting tubes of your digestive system to see how your body gets the energy it needs to survive!
What Happens to the Food You Eat?
Not at all! Your stomach is just one stop on a very long journey. The entire process takes place across a continuous tube that stretches from your mouth all the way to the other end of your body.
For energy and building materials! Food is fuel. Your digestive system breaks large pieces of food into microscopic molecules so your blood can carry them to every single cell in your body.
Put Your Instincts to the Test
Think about what you already know about your own body. Pick an answer for each question, then see if your instincts were right.
In the mouth! Digestion starts the second you put food in your mouth. Your teeth crush the food, and your saliva begins to break it down chemically.
About 7 metres long! It is coiled up incredibly tightly inside your abdomen so it can fit inside your body.
12 hours to 2 days! It is a very slow and careful process to ensure your body extracts every last drop of energy and water.
Understanding the Science
Let us break down the twisting tubes and powerful acids that turn your dinner into energy with Bill Nye the Science Guy.
Key Concepts
Digestion
Tap to learn moreDigestion is the essential process of breaking food down into molecules small enough to be absorbed by your cells. It is how your body turns solid matter into useable fuel.
The Mouth
Tap to learn moreThe Mouth is where the journey begins. Teeth mechanically mash the food, while saliva chemically breaks it down to make it soft and slippery.
Oesophagus
Tap to learn moreThe oesophagus is the long muscular tube that pushes food from the back of your throat straight down into your stomach using powerful waves of muscle contractions.
Stomach
Tap to learn moreThe stomach is a muscular sac that acts like a blender. It mashes the food and mixes it with powerful hydrochloric acid to break the food apart completely.
Chyme
Tap to learn moreChyme is the scientific name for the soupy, liquid mixture of partially digested food and acid that leaves the stomach and enters the intestines.
Small Intestine
Tap to learn moreThe small intestine is a coiled tube measuring about 7 metres long. This is where the body actively absorbs the vital chemicals and nutrients it needs to live.
Large Intestine
Tap to learn moreThe large intestine is the wider tube that comes directly after the small intestine. Its primary job is to absorb water back into the body to prevent dehydration.
Faeces
Tap to learn moreFaeces is the name given to the solid waste produced by the digestive system. It is made of anything your body cannot use or digest, and it is eventually pushed out of the body entirely.
Try It: The Digestive Journey Simulator
Take control of the human digestive tract! Select different types of food to eat and watch as the bolus travels down the oesophagus. Monitor the real time data panel to track stomach acid levels and watch the nutrients get absorbed!
Live Vitals
Apply Your Knowledge
Let us see if you can match the parts of your digestive tract to the specific jobs they perform.
Match the Concepts
Click an object to select it, then click the matching description to place it.
Real-World Challenge
Imagine you are a doctor advising an athlete before a major marathon. Based on how long different foods take to pass through the stomach, what type of meal should they eat to get quick energy without feeling sick during the race?
What Has Changed Since This Episode Aired
This episode first aired in the 1990s. While our digestive organs are still in the exact same place, our scientific understanding of the bacteria living inside them has completely revolutionised modern medicine!
Updated: No! In the 1990s, scientists understood the basic mechanics of the intestines, but we barely understood the billions of bacteria living inside them. We now know that trillions of microbes make up the "gut microbiome". These friendly bacteria are absolutely crucial for breaking down tough foods, making vitamins, and keeping our immune system strong.
Updated: It is far more advanced than that! Scientists have discovered that the gut has its own complex network of nerves. It is often called the "second brain" because it constantly sends chemical signals directly to our actual brain, profoundly affecting our mood, stress levels, and overall mental health.
Updated: Not anymore! Engineers have successfully built advanced artificial robotic stomachs in modern laboratories. These incredible machines perfectly mimic human digestion, complete with realistic muscle contractions and artificial stomach acid, allowing scientists to safely test exactly how new medicines and foods break down.
Test Your Understanding
Answer these questions and get instant feedback. How many can you get right?
Results
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Reflection
Your digestive system works constantly, completely automatically, without you even having to think about it. What is one new healthy food you could add to your diet to help your digestive system run more smoothly?
Episode Discussion
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