Absorption
Introduced| English | Meaning |
|---|---|
| absorption/əbˈsɔːpʃn/ | Taking a substance or energy into another material or system. |
| villi/ˈvɪlaɪ/ | Tiny finger-like projections of the small intestine wall that increase absorption area. |
| large intestine/lɑːdʒ ɪnˈtestɪn/ | The gut section where water is absorbed from undigested material. |
| faeces/ˈfiːsiːz/ | Material expelled from the digestive tract containing undigested food residues, bacteria and other waste. |
Getting food into the blood
- Once food is digested into small soluble molecules, it must pass into the blood to reach the cells.
- This is absorption 吸收, and it happens mainly in the small intestine.
Most absorption of digested food happens in the:
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The small intestine, lined with villi, absorbs digested food.
The tiny finger-like folds of the small intestine wall are called ______.
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Villi give the huge surface area for absorption.
Built for absorption
- The small intestine is very long and its wall is folded into millions of tiny villi 绒毛.
- This gives a huge surface area for absorbing digested food.
A villus has a thin wall, a capillary network and a lacteal for fast absorption
Absorption at the villi
The small intestine is lined with millions of villi that give a huge surface area for absorbing digested food.
Villi increase the rate of absorption by providing:
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Villi multiply the surface area for absorption.
Which adaptations of a villus speed up absorption? (Select all that apply.)
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A thick coating would slow absorption; the others speed it up.
Adaptations of a villus
- Each villus has a thin wall (one cell thick) for a short diffusion distance.
- A rich blood supply carries absorbed food away, keeping the gradient steep.
Most digested food molecules are absorbed in the large intestine.
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False. Digested food is absorbed mainly in the small intestine, through its villi. The large intestine absorbs most of the remaining water.
The large intestine 大肠
- The large intestine absorbs most of the remaining water.
- What's left (undigested fibre) is egested as faeces 粪便.
Surface area is everything for absorption. The villi (and microvilli on them) multiply the surface area enormously. A smooth gut would absorb food far too slowly to keep you alive.
You've got it
- absorption of digested food happens mainly in the small intestine
- villi give a huge surface area; thin walls + rich blood supply speed absorption
- the large intestine absorbs water; fibre is egested
Write from villi
- The small intestine lining is folded into villi.
- Each villus has a thin wall and many capillaries.
How do these features help absorption, and what does the large intestine absorb?
Absorption is fastest where the surface is huge and the path is short.
What do villi increase?
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Folds and villi multiply the absorbing surface.