Villi
Tiny finger-like folds lining the small intestine. They give a huge surface area to absorb digested food.
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Analogy
Like the loops on a towel that soak up more water than a flat sheet.
In practice
Each villus has thin walls and a rich blood supply so food passes quickly into the blood.
Practice
Flashcards
- Why do villi speed up absorption?They give a large surface area, thin walls and a good blood supply.
Questions people ask
Why are villi walls only one cell thick?
A thin wall means the digested food has a very short distance to travel to reach the blood. That makes diffusion and active transport quick. Together with a large surface area and a dense network of capillaries to carry the food away, it makes absorption very efficient.
What happens to food that is not absorbed?
Undigested material, mostly fibre, passes into the large intestine. There water is absorbed back into the body. What remains is compacted into faeces, stored in the rectum and removed through the anus. Fibre is important because it keeps food moving through the gut.