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Question

Describe the complete process of digestion along with all the enzymes involved in it.

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Solution

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.The chemical decomposition is done by the emzymes Amylase, Lipase, protease and nuclease.

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 undigested pieces of food and fiber. This is passed through to the rectum where it is stored until you go to the toilet!


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Structure of Digestive system
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