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.
The large intestine absorbs most of the remaining water.
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Water is reabsorbed there before faeces are egested.
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