Explain why the products of fat digestion enter the lacteals rather than the blood capillaries in the ileum, and describe what happens to these products after they leave the lacteals.

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

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

Model answer (4 marks)

Fatty acids and glycerol are too large/insoluble to enter the blood capillaries directly. Inside the enterocyte they recombine to form triglycerides (lipid droplets) which are then packaged into chylomicrons and released into the lacteals. The lacteals are lymphatic vessels, so the chylomicrons travel through the lymphatic system. The lymph eventually drains into the venous circulation, allowing the fats to enter the bloodstream and be transported to tissues.

Examiner tips

  • Mention size/solubility limitation of blood capillaries
  • Explain recombination into triglycerides and chylomicrons
  • State lacteals are lymphatic and describe drainage into blood

Common mistakes

  • Saying fats enter directly into blood capillaries
  • Confusing lacteals with blood capillaries
  • Omitting the lymphatic drainage step

Mark scheme (4 marks)

  1. Fatty acids and glycerol are too large / insoluble to enter blood capillaries directly
  2. Fatty acids and glycerol recombine to form fats / lipid droplets inside the epithelial cells before entering the lacteals
  3. The lacteals are part of the lymphatic system, so the absorbed fats travel through lymph vessels
  4. The lymphatic system eventually drains into the bloodstream, so the fats enter the blood and are transported around the body

Key terms in this question

lacteals

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