How the small intestine is adapted for its job.

How the small intestine is adapted for its job.

1. Very long with many folds.

   • This gives plenty of time for digestion to be completed and for nutrients to be absorbed.
   • About 5m long in an adult.

2. Has villi

   • Every villus has cells with even smaller projections called microvilli.
   • Gives inner surface of the small intestine a very large surface area
     • Food can be absorbed more quickly.
   • Contain blood capillaries (good blood supply).
   • Only one cell thick.
     • The digested food can easily cross the wall to reach the blood capillaries. Shorter diffusion path.

3. Concentration gradient maintained-helps diffusion.

   • Peristalsis constantly brings in a fresh supply of food, therefore high concentration gradient in the gut lumen.
   • Blood is flowing, constantly taking away the absorbed molecules therefore ensuring a low concentration here.