Mechanical and chemical digestion
Mechanical digestion physically breaks food into smaller pieces. Chemical digestion uses substances including enzymes to break large molecules into smaller molecules.
Digestive system
Follow food as it is broken down and nutrients are absorbed.
Class notes
Open PDF →Follow the meal
Chewing begins in the mouth. Swallowed food moves down the esophagus by muscular contractions called peristalsis, then mixes in the stomach before entering the small intestine.
Absorption and elimination
Most nutrient absorption happens in the small intestine. Nutrients enter blood or lymph and can be transported to cells. The large intestine absorbs water; remaining material is eliminated.
Travel through the digestive system
Select organs to investigate their roles in digestion.
Investigate
Find the stomach, small intestine and large intestine. Compare what happens in each.
Make the connection
Explain where food is broken down, where most nutrients are absorbed and where water is recovered. Food does not pass through the liver or pancreas.
If the model cannot load on your device, use the illustrated class notes above and the pathway below to trace the same structures.
Explore this idea further
Watch: The digestive system · Crash Course
Follow food as it is broken down and nutrients are absorbed.
Open on YouTube →How does a nutrient from lunch reach a muscle cell?
Reveal the reasoning
After digestion and absorption in the small intestine, the circulatory system transports nutrients to body tissues.
Try it yourself.
Explain one difference between chewing and the action of an enzyme.
Check your thinking
Chewing physically breaks food into smaller pieces. An enzyme helps chemically break molecules into smaller molecules.
Common question: Does digestion finish in the stomach?
No. Important digestion and most nutrient absorption occur in the small intestine.
Take it further.
Why is absorption necessary after a large food molecule is broken down?
See a possible explanation
Small nutrient molecules must cross the intestinal lining into blood or lymph to be transported to body cells.