The digestive system has three main functions: 1) Mechanical digestion through chewing and mixing food, 2) Chemical digestion through breaking down molecules in food, and 3) Absorption of nutrients into the bloodstream. Food travels through the mouth, esophagus, stomach, small intestine, large intestine, and rectum, with the small intestine absorbing nutrients through villi, which are tiny finger-like structures containing capillaries that nutrients diffuse into from the intestine.

1. Digestive System

2. What are the functions of the digestive system?
1. Mechanical digestion: chewing and mixing food
2. Chemical digestion: breaking down the
molecules in food, from big polymers into small
monomers
3. Absorption: when nutrients are absorbed from
food into the blood

3. Processing Piece:
• These both happen in the mouth. Label them
“mechanical digestion” and “chemical digestion”.
–Chewing food into smaller pieces
–Salivary amylase breaks down starch into glucose

4. What organs does food travel through
(or past) in the digestive system?
1) Mouth: Chews food to break it into smaller pieces.
Enzymes like amylase begin chemically breaking
down carbohydrates like starch.
2) Esophagus: a tube that connects the mouth to the
stomach. It moves food by squeezing itself to push
food down – this movement is called peristalsis.

5. What organs does food travel through in digestive system?
3) Stomach:
a muscular, U-shaped organ where carbohydrates are
broken down into monosaccharides and proteins are
broken down into amino acids.
- Stomach breaks down food using acid and digestive
enzymes like pepsin.
- Half-digested food in the stomach is “chyme.”

6. What organs does food travel through in digestive system?
4) Small intestine: 70 foot long tube where digestion
is completed. Lipids are broken down into fatty acids
and glycerol, and absorption begins.
- Small intestines are lined with “villi” which is where
nutrients are absorbed into the blood.
5) Large intestines: large tube where water is
absorbed into the blood
6) Rectum: stores waste before it is expelled from the
body.

7. Processing Piece:
Try to label the structures we talked about.

8. How do villi work?
• Vill

9. How do villi work?
• Villi are tiny, finger-like structures in the lining of
the small intestines.
• Nutrients in the small intestine diffuse (spread out)
through the cells in the walls of the villi into the
capillaries (tiny blood vessels) inside the villi.

10. Processing Piece:
• Draw a picture of the villi. Label the capillaries, and
show which way the nutrients from food diffuse.

11. What other organs are involved in the
digestive system?
1) Pancreas: organ that secretes (releases) digestive
enzymes into the small intestines to help break down
lipids.
2) Gallbladder: organ that secretes (releases) bile (a
soap-like chemical that breaks down fats) into the
small intestines to help break down lipids.

12. Exit Ticket
1. What is the function of the digestive system?
2. Describe the path that food takes through the
body, from mouth to rectum.
3. What part of the digestive system absorbs
nutrients?
4. Draw a picture of a villi. Label the capillaries, and
draw an arrow to show which way nutrients go.