What is the digestive fate of a fish finger sandwich?
What is the digestive fate of a fish finger sandwich?
A fish finger sandwich contains many essential foods, vitamins and minerals that our body needs for good health. The bread provides fibre that is needed to keep our digestive system fit, healthy and working. It also contains carbohydrates, which provide us with energy, and helps prevent constipation. The fish provides proteins, which are needed for growth, iron for keeping our red blood cells healthy, and iodine, which is used by the thyroid gland. The butter or margarine in the sandwich provides vitamins A and D for healthy skin, strong bones and teeth. Carbohydrates, Proteins and Fats are known as Macro Foods. Minerals and Vitamins are known as Micro Foods. The fats in the butter and fish provide us with energy. Unfortunately, these fats are saturated fats. Eating too much of these can damage our health. They stick to the lining of our blood vessels making them narrower, and can increase the risk of heart disease. For a complete balanced diet, the sandwich should also contain some vegetables such as lettuce, cucumber, tomatoes, etc, which contain lots of healthy vitamins and minerals, and no fat.
When we eat this sandwich, our body has to break down these large insoluble food molecules into small, soluble food molecules, so that they can be absorbed into the bloodstream. This process is called Digestion.
This sandwich, once put into the mouth and chewed will visit all eight bits of the Alimentary Canal. These include the Mouth, Oesophagus, Stomach, Liver, Pancreas, Large Intestine, Small Intestine and then the Rectum. The food is absorbed in the Villi and the waste will plop out of the Anus.
Enzymes are very important chemicals. They help digestion by ...
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When we eat this sandwich, our body has to break down these large insoluble food molecules into small, soluble food molecules, so that they can be absorbed into the bloodstream. This process is called Digestion.
This sandwich, once put into the mouth and chewed will visit all eight bits of the Alimentary Canal. These include the Mouth, Oesophagus, Stomach, Liver, Pancreas, Large Intestine, Small Intestine and then the Rectum. The food is absorbed in the Villi and the waste will plop out of the Anus.
Enzymes are very important chemicals. They help digestion by breaking down large food molecules into small food molecules. There are 3 main kinds of enzymes in our gut:
* A protein molecule, which is made up of many different amino acids.
* A starch molecule, which is made up of many glucose molecules.
* A fat molecule, which is made up of fatty acids and glycerol molecules.
The 3 kinds of enzymes that digest the Macro Foods are:
* Proteins, by Protease
* Carbohydrates, by Carbohydrase
* Fats, by Lipase.
Digestion starts in the mouth. The fish finger sandwich enters our mouth in bite size chunks. The salivary glands make Saliva, and this is mixed with the sandwich. Saliva contains a Carbohydrase enzyme called Amylase, and this starts to digest the Starch into Sugar.
The Oesophagus links the mouth to the stomach. It has circular muscles in its wall. These muscles contract and squeeze in behind the sandwich to push it along down the Oesophagus. In front of this food, the other muscles relax. This way of moving the food down the gut is called Peristalsis.
In the stomach, digestive juices are made and Pepsin is added. These contain hydrochloric acid. This is because the stomach protease works best in an acidic pH. Also, the acid in the stomach kills any germs or bacteria that the food may contain. The muscular walls churn up the sandwich, making sure that it is mixed up well with the juices. After a few hours of churning, the sandwich is no more, and now it is a runny substance. A ring of muscles open to let the food squirt out.
Next this liquid is passed onto the Liver where a substance called Bile is made. It is stored in the Gall bladder until it is needed.
In the Pancreas, 3 enzymes are made: Protease, which digest Proteins, Carbohydrase, which digest Carbohydrates, and Lipase, which digest Lipids (Fats). These enzymes carry on digesting and later, bile, which was made in the Liver, enters the Small Intestine from the bile duct. This substance is used to break up the fats. This increases the surface area of fats for lipase enzymes to act upon. Bile is alkaline and therefore neutralises the acid, which was added to the sandwich in the stomach. This gives the best pH for enzymes in the Small Intestine to work. Glands in the wall of the Small Intestine make intestinal juices. The 3 enzymes Carbohydrases, Proteases and Lipases are in it and eventually complete the digestion of the sandwich.
The Small Intestine is also well designed for absorption. This is because it has a thin lining, a good blood supply, and a very large surface area which is about 9 square metres. It is also very long, at least 6 metres long. It has a folded inner lining, and has millions of finger like processes called Villi (the singular of Villi is Villus). The Villus is only one cell thick. Amino acids, sugars, fatty acids and glycerol molecules are absorbed through the thin Villus wall, into the blood capillary.
When the digested sandwich gets to the Large Intestine, there is not much useful food left. It is mainly fibre, dead cells, bacteria and water. As it passes along the Large Intestine some of the water is absorbed into the blood. The solid waste or faeces are stored in the Rectum. Then eventually these are egested through the Anus.
In summary, we need a balanced diet in order to stay healthy. If any vitamins and minerals are missing from our diet, then we can become very ill. Water and fibre are also very important in our diet. Our digestive system has many parts to it, each of which performs different functions. When the process of digestion is complete, the food is absorbed into the blood, and waste food is passed out of the body through the Anus.
Essay by Harpreet Singh
(18th September 2002)
