Adaptations for efficient digestion and absorption

• Absorption of nutrients happens in the small intestine which has particular features which allow it to maximise the movement of substances through cells into the blood
• Features of Small Intestine to maximise Absorption:

  • Internal walls are folded into projections called villi (1mm in length)
• Features of Small Intestine to maximise Absorption:

  • Villi have THIN WALLS (one cell thick) to help keep diffusion pathway short
• Features of Small Intestine to maximise Absorption:

  • Villi have lots of capillaries to help maintain the concentration gradient by constantly transporting absorbed nutrients away
• Features of Small Intestine to maximise Absorption:

  • Villi contain muscles and can move which helps them to mix the contents of the ileum so that villi always have new material next to them to absorb nutrients. This helps to maintain the concentration gradient
• The epithelial cells that line the ileum have further adaptations for efficient digestion:

  • Microvilli (folded membrane) which increase the surface area for diffusion further
• The epithelial cells that line the ileum have further adaptations for efficient digestion:

  • Many mitochondria to provide energy for active transport
• The epithelial cells that line the ileum have further adaptations for efficient digestion:

  • Carrier proteins for active transport
• The epithelial cells that line the ileum have further adaptations for efficient digestion:

  • Channel proteins for facilitated diffusion