1. Exchange and absorption in the gut
• All should know the how the small intestine
maintains a large surface area
• Most will be able to describe and explain the
adaptations of the small intestine to maximise
absorption
• Some will be able to explain the role of active
transport in absorption

2. Stick me in label the structures and
add function if you can!

3. Exchange and absorption in the gut
The small intestine is the site of absorption of useful
molecules of digested food.
These molecules must pass across the lining of the small
intestine and enter the blood stream.
Their destinations are the cells of the body.
The absorption process must be very efficient to keep up with
the high demand of chemicals needed by our cells.

4. Exchange and absorption in the gut
• What molecules are absorbed?
• How do you think they are absorbed?
• Can you think of any features the small
intestine must have in order to be able to do
this?
• Watch video – Recap digestive system and
capsule endoscopy

5. The small intestine

6. Maximising the surface area
The result of this folding means that the surface area of
the lining of the small intestine is enormous!
Direction of Food
Epithelium
of small
intestine
This increases the number of places where small soluble
food molecules can pass across and move into the
blood.

7. Exchange and absorption in the gut
• Label and
explain the
adaptations
of the small
intestine

8. How are the villi adapted
• Villi have rich blood supply which provides steep
concentration gradient between the gut and the
blood.
• Short diffusion distances between the contents of the
gut and the blood (thin wall)
• All surfaces moist and all substances dissolved in
water.
• Each villus covered with microvilli which further
increase the surface area for diffusion.

9. Exchange and absorption in the gut
Coeliac
1. What has happened
to the villi of the
person with coeliac
disease?
2. What do you think Healthy
the consequences
are going to be?
3. What is going to
happen if that
person stops eating
wheat?