The inner wall of the small intestine contains folds, villi, and microvilli that increase the surface area for absorption of nutrients. Blood capillaries transport sugars and amino acids away from the small intestine, while lacteals transport fatty acids and glycerol. The colon absorbs water and mineral salts from undigested materials, the rectum temporarily stores feces, and the anus expels feces through defecation.

2. Objectives
1) Describe the structure of the inner wall of the small
intestine and explain it’s role in terms of increased
surface area for absorption of nutrients.
2) Explain the role of a lacteal and blood capillaries in the
transport and absorption of nutrients.
3) Describe the functions of the colon, rectum and anus in
relation to absorption of water and mineral salts,
temporary storage and egestion of faeces.

3. Digested food products,
mineral salts and water are
absorbed throughout the small
intestine especially in the ileum.

4. Video Time!

5. Inner wall of small intestine
Folds
Villi – minute finger like projections

6. Inner wall of small intestine
Fold
Villi – minute finger like projections
Microvilli

7. Inner wall of small intestine
Why is there a need for numerous folds, villi
and microvilli?
To increase surface area for absorption of digested
food substances – Increasing the absorption rate of
water and digested food products

8. Blood
capillaries
Lacteal
Sugars, amino acids, are absorbed
by diffusion into the blood
capillaries
Blood capillaries transport sugars
and amino acids away from the
small intestine.
Glycerol and fatty acids diffuse
into the epithelium – form fat
globules – enter the lacteals
Lacteal transport fats away from
the small intestine.
Epithelium
Villi
One cell
thick
Faster diffusion
of the digested
food products
What is the epithelium
one cell thick?

9. Would the absorption of
nutrients be affected if
digested food substances
cannot be transported
away by the blood
capillaries?
Explain your answer.
Yes. To a certain extent

10. The continual transport of
digested food substances
maintains a concentration
gradient for the absorption of
digested food substances by
diffusion
Lower concentration of digested
food substances in the lumen of the
small intestine, glucose and amino
acids are absorbed by active
transport
Mineral salts enter the blood
capillaries by active transport

11. Activity time!
I need a
doctor!

12. I need a doctor!
You are a doctor that specializes on
the ileum. As the doctor of a
patient who is overweight and has
the intentions to lose weight, what
procedures can be done to help
the patient lose weight? Explain
your answer.

13. Large intestine
Colon
• Absorb water and mineral salts
from undigested food materials
Rectum
• Temporarily stores the faeces
• When the rectum contracts,
faeces is expelled through the
anus
Anus – Egestion/defaecation of faeces

14. Let’s Review
1) Describe the structure of the inner wall of the small
intestine and explain it’s role in terms of increased
surface area for absorption of nutrients.
2) Explain the role of a lacteal and blood capillaries in the
transport and absorption of nutrients.
3) Describe the functions of the colon, rectum and anus in
relation to absorption of water and mineral salts,
temporary storage and egestion of faeces.

15. Write 3 key things that you learn
today
What am I still unsure about?