Absorption
| English | Chinese | Pinyin |
|---|---|---|
| absorption | 吸收 | xī shōu |
| villi | 绒毛 | róng máo |
| large intestine | 大肠 | dà cháng |
| faeces | 粪便 | fèn biàn |
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:
The small intestine, lined with villi, absorbs digested food.
The tiny finger-like folds of the small intestine wall are called ______.
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:
Villi multiply the surface area for absorption.
Which adaptations of a villus speed up absorption? (Select all that apply.)
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.
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