AQA 312 The digestive system

  • The digestive system is a series of linked organs which work together to process food.
  • The functions involve the enzymatic hydrolysis of food molecules and the absorption of the products of this breakdown.
Organ/Gland Function Structure Role
Oesophagus Carries food from mouth to stomach Muscular wall or peristalsis Transport
Stomach Stores and digests food. Kill bacteria by having a pH of 2 Muscular sac with inner layer that releases acid and enzymes Digestion
Small Intestine Digests food using enzymes released from its walls. High surface aids absorption A long muscular tube with folded walls to increase the surface area Digestion/Absorption
Large intestine Absorption of water and the formation of faeces Muscular tube Absorption
Salivary glands Releases saliva containing amylase of starch digestion Glands near mouth Digestion
Pancreas Releases pancreatic juice which contains digestive enzymes into the small intestine. Large leaf-shaped gland close to stomach Digestion


  • Digestion is the chemical breakdown by hydrolysis of large insoluble food molecules by enzymes into smaller more soluble molecules that can be absorbed and assimilated.
  • Digestion may be mechanical (mastication, chewing) or chemical (enzymatic, acidic).
  • Some of the main food molecules of note are proteins and carbohydrates.

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