Absorption — Cambridge IGCSE Biology
Where nutrients and water are absorbed, and how the structure of a villus is adapted for absorption in the small intestine.
Revision notes
2 short notes, in the order of the specification. Each one in short:
Absorption is the movement of nutrients from the intestines into the blood. Nutrients are absorbed in the small intestine, mostly in the ileum. Most water is also absorbed from the small intestine, and some is absorbed from the colon. The undigested food left is stored in the rectum as faeces and removed by egestion.
Villi and microvilli
SupplementVilli are tiny finger-like projections lining the small intestine, and the cells on their surface have even smaller projections called microvilli. Together they greatly increase the internal surface area for absorption. Each villus has a wall one cell thick, a network of capillaries that absorb glucose and amino acids, and a lacteal that absorbs fatty acids and glycerol.
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Quick check questions
Where are nutrients absorbed?
Show answer
The small intestine.
Where is most water absorbed?
Show answer
The small intestine (some is absorbed in the colon).
Supplement What is the role of villi and microvilli?
Show answer
They increase the internal surface area of the small intestine.
Supplement What does the lacteal absorb?
Show answer
Fatty acids and glycerol.
Frequently asked questions
How is the small intestine adapted for absorption?
Supplement The small intestine is lined with villi, and the cells on each villus have microvilli, which greatly increase the surface area for absorption. Each villus has a wall only one cell thick, so the distance is short, and a network of capillaries gives a good blood supply that carries nutrients away and keeps absorption going.
Where is water absorbed in the digestive system?
Most water is absorbed from the small intestine, and some is also absorbed from the colon. The small intestine also absorbs nutrients such as glucose, amino acids, fatty acids and glycerol, vitamins and mineral ions. In an exam, say 'mostly in the small intestine and some in the colon', not 'colon only'.
What is the function of the lacteal in a villus?
Supplement The lacteal is a lymph vessel in the centre of each villus. It absorbs fatty acids and glycerol and carries them away in the lymph. The capillaries in the villus absorb glucose and amino acids into the blood instead, and the flowing blood carries them away so absorption keeps going.
Written and checked against the Cambridge IGCSE Biology (0610) specification · Updated October 2026