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Home > Anatomy & Physiology > Digestive System

The Human Digestive System

 

The Functions of the Digestive System.

The primary function of the digestive system is to break down food both mechanically and by the use of enzymes, so that it can be used by the body for energy and cell growth and repair. The human digestive system consists of a large number of organs and processes with the combined functions of breaking down our food into smaller molecules which can be used to produce energy and for other nutritional purposes; and excreting the waste consumed and produced by the system.

What is the Digestive System ?

How does the Digestive System work ? Digestion essentially occurs in a series of tubes such as the Oesophogus and Intestines as food passes through the body. A number of other organs contribute to digestion by providing enzymes for the breakdown of food. The anatomy of the digestive system can be seen in the diagram below.

Digestive System Organs

Mouth: The mouth is the starting point of digestion. Here the process of chewing starts to break down food and enzymes such as salivary lipase and amylase also start to chemically break down the food.

Oesophagus: Once you swallow the food moves into the Oesophagus where continual waves of involuntary contraction push the food into the stomach.

Stomach: The stomach has both a mechanical and a chemical function in digestion. The upper part of the smooth (involuntary) stomach muscle relaxes to allow a large volume of food to be stored. The lower muscle then contracts in a rhythmical manner in order to churn the food inside and mix it together with the gastric acid (mainly hydrochloric acid) and digestive enzymes Pepsin, Gelatinase and Gastric Amylase and Lipase which break it down further. The stomach must then empty its contents into the small intestine.

Small Intestine: Whilst in the small intestine food is subjected to yet more enzymes, those from the Pancreas and from the glands within the intestine walls which break down carbohydrates and proteins. It is also mixed with a product of the liver which is stored and released into the intestine by the gall bladder. This is commonly known as bile. Bile works to dissolve fat so that it can be digested by the other enzymes. Rhythmic smooth muscle contraction continues within the small intestine and pushes the digesting food through its narrow tube.

Once the food is completely broken down into its individual components it is absorbed through the intestinal walls, into the blood flow of the capillaries which surround the intestine. To make this process faster and more efficient the intestinal walls contain numerous folds which are covered in finger-like projections called villi. This vastly increases the surface area of the intestine wall for molecules of digested food to pass through.

Large Intestine: The large intestine continues the foods journey and is the bodies last chance to absorb any water and minerals still remaining. The rest of the contents of the large intestine is waste such as undigestable pieces of food and fiber. This is passed through to the rectum where it is stored until you go to the toilet!

Picture Diagram of the Digestive System

 

Digestive System Quiz

1. List, in correct order, the passage of food through the digestive system










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1. List, in correct order, the passage of food through the digestive system



  • Mouth
  • Oesophogus
  • Stomach
  • Small intestine
  • Large intestine


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2. What are the mechanical and chemical functions of the stomach?










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2. What are the mechanical and chemical functions of the stomach?



  • The mechanical function is contraction of the smooth muscle in the stomach wall which acts to churn the food
  • The chemical function is the presence of enzymes and gastric acid to break down the food


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3. What is the function of Bile and where is it released?










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3. What is the function of Bile and where is it released?



  • Bile is released into the small intestine from the gall bladder. Bile dissolves fat.





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4. What is the function of the villi and where are they found?










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4. What is the function of the villi and where are they found?



  • The villi are found in the small intestine and their function is to increase the inner surface area of the intestine making it easier for molecules of digested food to pass through



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5. Where do the required nutrients go to from the small intestine?










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5. Where do the required nutrients go to from the small intestine?



  • They pass through the small intestine wall into the capillaries which surround the intestine





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Digestive System Diagram

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