Absorption
Absorption
- Digested nutrients are absorbed into the blood in the small intestine.
- Its inside is covered with tiny villi.
- These are perfectly adapted for fast absorption.
Practice
Most digested food is absorbed in the:
The small intestine, lined with villi, absorbs the digested nutrients into the blood.
Villi
- The small intestine is lined with millions of finger-shaped villi, each covered in even smaller microvilli — a huge surface area.
- Each villus has:
- a wall just one cell thick (a short distance to cross),
- a network of capillaries that carry away glucose and amino acids,
- a lacteal in the centre that carries away fatty acids and glycerol.
Practice
Villi are well adapted for absorption because they give:
Millions of villi (with microvilli) give a huge surface area, and a one-cell-thick wall gives a short distance.
Practice
Match each vessel in a villus to what it carries away.
Capillaries carry glucose and amino acids; the lacteal carries fatty acids and glycerol.
You've got it
Key idea
- nutrients are absorbed in the small intestine (most water too; the colon absorbs the rest)
- villi + microvilli give a huge surface area; a one-cell-thick wall gives a short distance
- capillaries carry glucose/amino acids; the lacteal carries fatty acids + glycerol