Describe how the structure of the ileum is adapted to allow efficient absorption of the products of digestion into the bloodstream.

Cambridge International IGCSE Biology (0610) — 7.5 Absorption · Describe · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

The ileum has a large internal surface area due to the presence of villi.
Villi contain a dense network of capillaries that quickly carry absorbed nutrients away, maintaining a concentration gradient.
The epithelial cells lining the villi possess microvilli, which further increase the surface area for absorption.
Lacteals within the villi absorb the products of fat digestion (fatty acids and glycerol) into the lymphatic system.

Examiner tips

  • Use the exact terms: villi, capillaries, microvilli, lacteals. Show the sequence: villi → capillaries → microvilli → lacteals. Mention the concentration gradient and lymphatic uptake of fats.

Common mistakes

  • Confusing the ileum with the jejunum or colon. Omitting the role of lacteals in fat absorption. Using vague phrases like "large surface area" without specifying villi and microvilli.

Mark scheme (4 marks)

  1. The ileum has a large internal surface area due to the presence of villi
  2. Villi have a rich blood supply / dense network of capillaries to carry absorbed nutrients away quickly, maintaining a concentration gradient
  3. The epithelial cells lining the villi have microvilli which further increase the surface area for absorption
  4. Lacteals inside the villi absorb the products of fat digestion (fatty acids and glycerol) into the lymphatic system

Key terms in this question

absorption

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