Enzymes and their role in digestion II

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  • Enzymes and their role in digestion
    • 5. The Ileum (small intestine)
      • It is adapted for the absorption of food in a number of ways (ensures diffusion of food into the blood takes place rapidly):
        • process of absorption is aided by a good blood supply and thin permeable membranes of the cells that line the ileum
        • folded which greatly increases the surface area
        • over 6m in length
      • Soluble food is mainly absorbed by diffusion.
        • Soluble sugars, amino acids and other products of digestion will be in high concentration in the lumen of the small intestine.
        • They will be in low concentration in the blood.
        • Therefore, these molecules will diffuse into the blood from the lumen.
        • The process of diffusion takes place more rapidly when:
          • large surface area
          • steep concentrationgradient
          • short diffusion pathway
      • The villi help absorption by:
        • the villus has a thin and permeable surface lining - there is a single layer of epithelial cells between the lumen of the gut and the capillaries and lacteals
        • their finger-like shape and microvilli on the surface epithelial cells provide a large surface area for absorption
        • they have an excellent blood supply - each villus has an extensive capillary network, which means the whole small intestine is well supplied with blood to transport the absorbed products of digestion (helps maintain a steep concentrationgradient)
      • The lacteal absorbs the break down products of fates before returning them to the blood.
    • Following digestion the absorbed food molecules travel in the blood to the liver.
      • In the liver excess amino acids will be broken down to produce urea, a soluble waste product removed from the blood by the kidneys.
        • Excess glucose, under the influence of insulin secreted from the pancreas, will be converted to glycogen in the liver for storage.


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