CIE IGCSE Biology

Revision Notes

7.5 Absorption

Absorption of Food & Water

  • Absorption is the movement of digested food molecules from the digestive system into the blood (glucose and amino acids) and lymph (fatty acids and glycerol)
  • Water is absorbed in both the small intestine and the colon, but most absorption of water also happens in the small intestine
  • Absorption takes place in the second section of the small intestine, the ileum
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How is the Ileum Adapted for Absorption?

  • The ileum is adapted for absorption as it is very long and has a highly folded surface with millions of villi (tiny, finger like projections)
  • These adaptations massively increase the surface area of the ileum, allowing absorption to take place faster and more efficiently
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Structure & Adaptations of a Villus

Adaptations-of the small intestine, IGCSE & GCSE Chemistry revision notesAdaptations of the small intestine

 

  • Microvilli on the surface of the villus further increase surface area for faster absorption of nutrients
  • Wall of villus is one cell thick meaning that there is only a short distance for absorption to happen by diffusion and active transport
  • Well supplied with a network of blood capillaries that transport glucose and amino acids away from the small intestine in the blood
  • Lacteal runs through the centre of the villus to transport fatty acids and glycerol away from the small intestine in the lymph

Exam Tip

The way in which the structure of a villus is related to its function comes up frequently in exam questions so it is worth ensuring you have learned these adaptations.

Author: Jenna

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.
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