Adaptations of the Small Intestine (Cambridge O Level Biology)

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Adaptations of the Small Intestine

  • The ileum is adapted for absorption because it is very long and has a highly folded surface with millions of villi (tiny, finger-like projections)
  • Each cell that forms part of a villus has folds in its cell membrane, called microvilli
  • These adaptations massively increase the surface area of the ileum, allowing absorption to take place faster and more efficiently

Adaptations of the Small Intestine for Absorption Diagram

Adaptations of the small intestineAdaptations of the small intestine

  • Microvilli on the surface of the villus further increase surface area for faster absorption of nutrients
  • The wall of the 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
  • The Lacteal runs through the centre of the villus to transport fatty acids and glycerol away from the small intestine in the lymph

A Single Intestine Epithelial Cell Showing Microvilli Diagram

microvilli-on-a-single-epithelial-cell

Each individual cell that lines the intestine contains folds in its membrane called microvilli

Examiner 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.

Don't confuse villi and microvilli. A villus is a structure made up of many thousands of cells. Microvilli are the foldings of the membranes of individual cells and can only be seen under a microscope. Both combine to increase the overall surface area for absorption. 

Hepatic Portal Vein

  • In the intestine, a lot of important food molecules, ions and water are absorbed into the blood across the intestinal wall
  • This blood leaves the intestines with no oxygen but with a heavy load of nutrients that are needed by the rest of the organs and tissues
  • A separate vein, the hepatic portal vein, carries this blood to the liver from the intestine
  • The liver plays an important role in processing different food molecules during assimilation
  • Beyond the liver, the food molecules continue their journey around the double circulation system until they reach their destination cells 
    • The liver can also detoxify certain chemicals that might have been ingested by accident

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Phil

Author: Phil

Expertise: Biology

Phil has a BSc in Biochemistry from the University of Birmingham, followed by an MBA from Manchester Business School. He has 15 years of teaching and tutoring experience, teaching Biology in schools before becoming director of a growing tuition agency. He has also examined Biology for one of the leading UK exam boards. Phil has a particular passion for empowering students to overcome their fear of numbers in a scientific context.