Biology · StudentHub Lesson
Digestive System
How the body breaks down food into nutrients that can be absorbed and used.
What you will learn
- List the main organs of the digestive system
- Describe the path food takes through the body
- Explain mechanical vs chemical digestion
- Describe the role of enzymes
- Explain nutrient absorption in the small intestine
Watch the lesson
The Digestive System: CrashCourse Biology #28 · CrashCourse
Watch on YouTubeTopic notes
Main Idea
The digestive system breaks down food into nutrients the body can absorb and use for energy and growth.
Key Concepts
- Digestion includes mechanical and chemical breakdown
- Enzymes speed up chemical digestion
- Nutrients are absorbed mainly in the small intestine
Definitions
- Enzyme: protein that speeds up digestion reactions
- Peristalsis: wave-like muscle contractions moving food
- Villi: finger-like projections in the small intestine that absorb nutrients
Processes
- Mouth: chewing and saliva begin digestion
- Esophagus: peristalsis moves food to stomach
- Stomach: acid and enzymes break down food
- Small intestine: nutrients absorbed
- Large intestine: water absorbed, waste formed
Examples
Starch is broken into sugars by amylase in saliva, an example of chemical digestion.
Common Mistakes
- Thinking digestion only happens in the stomach
- Confusing the small and large intestine's roles
- Forgetting the role of enzymes
Key concepts
Important terms
- Enzyme
- A protein that speeds up chemical reactions like digestion.
- Peristalsis
- Wave-like muscle contractions that move food through the digestive tract.
- Villi
- Small projections in the small intestine that increase surface area for absorption.
Quick revision
- Digestion starts in the mouth
- Stomach uses acid and enzymes
- Small intestine absorbs nutrients
- Large intestine absorbs water
- Peristalsis moves food along
- Enzymes speed chemical digestion
- Villi increase absorption surface area
Check your understanding
Question 1 · Multiple choice
Where does most nutrient absorption occur?
Question 2 · Multiple choice
What is peristalsis?
Question 3 · True or false
The large intestine mainly absorbs water.
Question 4 · Short answer
What is the role of enzymes in digestion?
Question 5 · Short answer
Name the structures that increase absorption surface area in the small intestine.
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