How the small intestine is adapted for its job.

Very long with many folds.
1. This gives plenty of time for digestion to be completed and for nutrients to be absorbed.
2. About 5m long in an adult.
Has villi
1. Every villus has cells with even smaller projections called microvilli.
2. Gives inner surface of the small intestine a very large surface area
  1. Food can be absorbed more quickly.
3. Contain blood capillaries (good blood supply).
4. Only one cell thick.
  1. The digested food can easily cross the wall to reach the blood capillaries. Shorter diffusion path.
Concentration gradient maintained-helps diffusion.
1. Peristalsis constantly brings in a fresh supply of food, therefore high concentration gradient in the gut lumen.
2. Blood is flowing, constantly taking away the absorbed molecules therefore ensuring a low concentration here.

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	Creado por glhoward13 hace casi 11 años