Food and Digestion
http://peer.tamu.edu/curriculum_modules/organsystems/module_2/activity4.htm
Digestion
Can you imagine having a 30-foot-long tube running from your mouth to your anus? That is exactly what you have in your digestive system. Food contains nutrients, proteins, carbohydrates, and fats that the cells in our body use as energy. The process of digestion involves breaking down the food so that cells can use its components to fuel our body and keep it functioning. This module explains how organisms digest, absorb, and utilize food to obtain the materials they need for their cells to sustain life, grow, and multiply.Usually in biological science, we learn most of what we know from studies of animals. But some of our first notions of what happens in digestion comes from the study of a live human patient who had an unhealed wound that led from the stomach to the outside. Read the interesting Story Time of Dr. Beaumont and his patient.
Why do we need a digestive tract?
If the body did not have a digestive tract, you could not enjoy your favorite pizza, hamburger, or other food. The human body must obtain its energy by eating food. Therefore, the main purpose of the digestive system is to provide the body with amino acids, carbohydrates, fats, and vitamins to keep our cells functioning. The digestive system provides these essential materials to the 75 trillion cells that live in our bodies. Wow! Do you know how many 75 trillion is?
The digestive tract takes both liquids and food and breaks them down into single molecules that can be absorbed by cells in the small intestine. These cells transport the molecules into the blood stream so that other cells in the body can use them. The digestive tract also serves to eliminate what your body doesn't absorb during the digestive process.
Why do I have a stomach?
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Why do you have two intestines?
The intestines are where the body absorbs all of the food, vitamins, fluid, and minerals that you eat. The intestines are long giving your body a greater opportunity to absorb more of what you eat. The small intestine breaks down proteins, carbohydrates, and fats so that they can be absorbed into the body and the bloodstream. The large intestine is where moisture is absorbed from what is left of the food. Anything that is not absorbed by the intestines is then passed through as solid waste (or feces).
Why are the liver and pancreas important in digestion?
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How we find out?
Over the years scientists have worked to unlock the once mysterious process of how humans digest food. Some of the approaches can even be used by you to discover what happens in the digestive tract!
How do we learn about the different parts of the digestive system?
When we dissect a dead animal, we can see the different parts along the tract that begins in the mouth and ends in the anus. See pictures here. The cells can be seen by making microscope slides.
How could we see where digestion begins?
How would you find out if saliva has any digestion function? A quick way to find out is to compare a piece of steak (which has a lot of protein) and a cracker (which has a lot of starches). Place the meat in your mouth and do not chew it for about 2 minutes. What happens? You should discover that the steak keeps its shape. Next, place the cracker in your mouth without chewing it for about two minutes. You should notice that the cracker becomes soft in your mouth and you may even taste something sweet. This is because the cracker is composed of carbohydrates, which saliva is able to digest at least partly. The carbohydrates in the cracker begin to be broken down into individual glucose molecules by an enzyme in your saliva. This enzyme only breaks down carbohydrates, not proteins. Since the steak was mostly composed of proteins, it did not start breaking down like the cracker.
How do we know what goes on in our stomach?
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WHAT WE KNOW?
Digestive Structures and Functions
Over the years scientists have learned a lot about the digestive tract that has given doctors and researchers in the health science field the necessary information to cure or treat most of the digestive disorders that face us today.
Is pizza good for me?
Pizza contains the three major types of food your body needs to function and some essential vitamins, but it also contains cholesterol, which can cause blockage in your blood vessels. Pizza is very high in calories and fat.
What organs are involved in digestion?
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The time food stays in the various parts of the digestive tract in a human under normal conditions is approximately as follows:
• Stomach: 4-6 hours
• Small intestine: 2-4 hours
• Large intestine: 24-48 hours
Knowing this, you should be able to answer the following:
1. Why do you get hungry at the times for breakfast, lunch, and dinner?
2. Why should you have a bowel movement every day or two?
STORY TIME:
William Beaumont (1785-1853)
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Beaumont was able to directly observe the release of stomach secretions in response to Alexis' eating different foods. He was also able to collect stomach contents, place them in glass tubes, and observe how much food was digested and the length of time it took for the food to break down. For centuries, many people believed that the stomach was hot and somehow "cooked" the food, acting as a fermenting vat or grinding mill. Beaumont, with the help of Alexis, proved that those superstitions were false.
Medicine in the early nineteenth century was primitive. Doctors did not realize the importance of cleanliness. For the pain of rheumatism, Beaumont and fellow doctors prescribed opium, wood resin, and turpentine. Despite such uninformed and primitive medicine, Beaumont proudly claimed that none of his 200+ patients died.
COMMON HAZARDS:
Ulcers
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The leading cause of ulcers is a recently discovered bacterium. This bacterium, Helicobacter pylori (photo on left), was discovered in the early 1990's by a veterinarian who was studying ulcers in pigs. This bacterium resides in about 30% of the population; these individuals have a much greater risk of developing ulcers.
The chances of any person getting an ulcer are increased if they are exposed to certain chemicals or emotions. Nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin, ibuprofen, or stronger medications used in the treatment of arthritis or chronic inflammatory disease and ethyl alcohol (alcohol in alcoholic beverages) can weaken or break the mucus barrier that normally protects stomach cells from the acid. An ulcer can also be caused by stress and anxiety because these emotions cause an increase in the amount of HCl secreted by the cells of the stomach. Patients that suffer from severe infections or injuries are at a much greater risk of developing ulcers due to a breakdown in the mucus lining of the stomach.
Treatment
Treatment of ulcers includes the use of drugs to treat bacteria, reduce stomach acid, and protect the stomach lining. Antibiotics are used to treat bacteria, antacids are used to reduce stomach acid, and bismuth subsalicylate, a component of Pepto-Bismol®, is used to protect the mucus lining of the stomach. The most effective way to combat ulcers is a two-week treatment of these three types of drugs.
To learn more about ulcers visit the following websites: