Lesson · S.1.4

The digestive system

How food is broken down and absorbed on its way from mouth to anus, and where mechanical and chemical digestion each take over.

ObjectiveS.1.4Read2 minExam weightHuman Anatomy and Physiology ≈ 41% of Science

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What you will be able to do

  • Distinguish mechanical digestion from chemical digestion.
  • List the organs food passes through, from the mouth to the anus, in order.
  • Identify where protein digestion begins and where most nutrient absorption happens.

What the lesson concludes

  • Mechanical digestion breaks food apart physically, chemical digestion breaks it apart with enzymes, and they run at the same time from the mouth onward.
  • Protein digestion begins in the stomach, since pepsin needs the stomach's acidic environment to work.
  • Most nutrient absorption happens in the small intestine, through villi and microvilli.
  • Bile helps digest fat but is not itself an enzyme, a distinction the TEAS likes to test.
  • The large intestine's main jobs are absorbing water and salt and hosting bacteria that ferment waste.