What are the two main roles of the digestive system? Describe each.

1Digestion - process of breaking down large food molecules into smaller molecules.


2Absorption - process of absorbing these small food molecules into the body.

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Name all the organs that food passes through, from the point it's eaten to the point waste is excreted (pooped out). 

  1. Mouth
  2. Oesophagus
  3. Stomach
  4. Small intestine
  5. Large intestine
  6. Rectum
  7. Anus

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What is the role of the teeth?

Teeth chew food and physically break it down into smaller pieces.


This has two purposes:

1It increases the surface area for enzymes to act on.

2It make the food easier to swallow.

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What is the oesophagus (or 'gullet')?

A muscular tube that carries food from the mouth to the stomach.

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What are the three things does the stomach does to aid digestion?

  1. The stomach contracts its muscular walls to churn and mix the food.
  2. It produces pepsin, which is a type of protease enzyme, and breaks proteins down into amino acids.
  3. It produces hydrochloric acid, which a) provides the right pH for pepsin to function, and b) kills microorganisms.

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Where is bile made and stored?

Bile is made by the liver, but is stored in the gallbladder.

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What are the two roles of bile?

  1. To emulsify lipids, which means separate large droplets of lipid into smaller droplets - this increases the surface area, and means that lipase enzymes can break them down more quickly.
  2. To neutralise the acid from the stomach, which bile can do because it is alkaline - this makes the pH more neutral, which is more optimal for enzymes.  

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What is the role of the salivary glands?

They produce saliva, which has two purposes:


  1. It moistens food which makes it easier to swallow.
  2. It contains salivary amylase which digests starch to maltose.

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Which enzyme(s) does the pancreas produce?

  1. Carbohydrases (e.g. amylase).
  2. Proteases.
  3. Lipases.

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Which enzyme(s) does the stomach produce?

Proteases (e.g. pepsin). 

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Which enzyme(s) does the small intestine produce?

  1. Carbohydrases (e.g. amylase).
  2. Proteases.
  3. Lipases.


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What are the two roles of the small intestine?

  1. It is where most digestion takes place.
  2. It is where nutrients are absorbed into the bloodstream.

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What is the main role of the large intestine?

To reabsorb water.

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What is the main role of the rectum?

To store faeces until they're ready to be released.

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Give four ways in which villi are adapted to their role.

  1. There are many villi - giving them a large total surface area over which to absorb nutrients.
  2. Their walls have only a single layer of cells - nutrients only have to diffuse a short distance.
  3. They have a good supply of blood ('internal medium') - this maintains a strong concentration gradient between the lumen and the blood.
  4. The cells lining the villi have microvilli on their surface - further increasing the surface area.

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