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Tracing the journey of food as it is broken down into energy for the body.
Imagine if you could shrink down to the size of a crumb and ride a piece of pizza through a giant, winding, 30-foot-long tunnel inside your own body!
Digestion starts before you even take a bite! When you smell something delicious, your mouth makes saliva (spit). Saliva contains special chemicals called enzymes that start breaking down starches. Your teeth perform mechanical digestion by grinding food into a soft ball called a bolus. Once you swallow, the bolus travels down the esophagus, a stretchy tube that uses muscle squeezes called peristalsis to push food toward your stomach. Think of it like squeezing a tube of toothpaste from the bottom to the top!
Quick Check
What is the name of the muscle movement that pushes food down the esophagus?
Answer
Peristalsis
The stomach is like a powerful mixer. It uses strong muscles to churn food and mixes it with gastric acid. This acid is very strong, but your stomach has a special mucus lining to protect itself! The acid kills bad bacteria and breaks proteins into tiny pieces. After about to hours of mixing, your food has turned into a thick liquid called chyme. It is now ready for the next stage of the journey.
Imagine a balloon filled with orange juice and crackers. 1. Squeezing the balloon represents the stomach muscles churning. 2. The orange juice represents the gastric acid breaking the crackers down. 3. The resulting mush is what chyme looks like!
Quick Check
What is the name of the thick liquid food turns into inside the stomach?
Answer
Chyme
Most of the 'magic' happens in the small intestine. Despite its name, it is about feet long in an adult! This is where nutrients (the good stuff in food) are absorbed into your blood. The walls are covered in millions of tiny, finger-like bumps called villi. These villi act like tiny sponges, soaking up vitamins and minerals. Without villi, your body wouldn't get the energy it needs to run and play.
Why are villi shaped like fingers instead of being flat? 1. A flat towel can only soak up a little water. 2. A fluffy towel with many loops (like villi) has more surface area. 3. More surface area means the small intestine can absorb nutrients times faster!
Which part of the digestive system uses villi to absorb nutrients?
What is the main job of saliva in the mouth?
The stomach is the place where most nutrients are absorbed into the blood.
Review Tomorrow
In 24 hours, try to explain to a friend or family member what 'peristalsis' is and where 'villi' are located.
Practice Activity
During your next meal, count how many times you chew one bite. Remember that your teeth are starting the very first step of digestion!