Describe how the small intestine is adapted for efficient absorption.

Hi, I hope this helps:
1. The inner wall of the small intestine has walls which are just one cell thick, meaning there is a shorter distance for diffusion and active transport to occur.
2. There are many tiny structures known as villi in the small intestine (which are covered in smaller projections called microvilli); these increase the surface area of the small intestine, allowing absorption to occur faster. Also, the intestine walls are folded - this increases surface area.
3) The small intestine is very long, meaning it has a large surface area (it has a length of about 5m)
4) Villi contain many capillaries which provide good blood flow and rapid removal of the products of digestion into the bloodstream, thereby increasing the concentration gradient.

That's as much as I can find, so hopefully that helps a lot. I would really recommend checking out the videos from this guy (I've put a link to his video on absorption in the small intestine below) and also BBC Bitesize - you can have a more detailed look on there and can narrow the content down to your specific exam board.
https://www.youtube.com/watch?v=5VW5-VXlWic

Hope this helps with your summer work