organisation - absorption in the small intestine

Question 1

what are the adaptations of a small intestine?

Answer 1

• very long around 5m so provides a very large surface area for absorption of molecules for digestion
• inside covered in villi increasing surface area

Question 2

how are villi adapted in the small intestine?

Answer 2

• surface of villi covered in microvilli increasing surface area further
• good blood supply so bloodstream rapidly removes products of digestion increasing concentration gradient
• thin membrane ensures a short diffusion path

Question 3

what do all of these features mean?

Answer 3

rapid rate of diffusion

Question 4

what happens to any molecules which can’t be absorbed by diffusion?

Answer 4

absorbed by active transport