I. PRECEDENCE
I.1. Background
Digestive system has relationship with the receiving of food and prepare it to assimilated by body. The digestive track consists of :
Mouth Pharynx Esophagus Stomach Small Intesine Large Intestine
Besides, mouth consists teeth to chewing food and tongue to help tastes the food and swallow it. Some glands or group of glands pour important digestive liquid to digestive track. They are salivary glands with the track into the mouth, Pancreas and hepar Glands.
All digestive track is bordered by mucous membrane from genital labia until the end of esophagus, plus epithelium layers.
During the digestive process, food becomes simple structures that can be absorbed and used by cell and tissue of body. The changing of food’s characteristic is because the enzym’s activities in the liquid digestive. Each enzym has a specific task-filter and work by a single food element and has no effect to other elements of food.
I.2. Problem’s Formulation
Digestive system consist of digestive track, glands and organs of it. Food is stranded by enzym in the digestive track and carried by blood to liver and finally to tissue.
I.3. Problem’s Scope
The scope of this working paper :
1. Definition of Digestive system
2. The principal Organs of Digestion
3. How food is digested
4. How the digestive process is controlled
5. The advantage of digestive system
6. Thed diseases of digestive system
I.4. Systematic of Writing
This task is made by looking for informations in many literatures : internet, books and dictionary. This kind of method called librarian method. After get all informations I need, I join it into one to make the better datas.
II. CONTENTS
II.1. Definition of digestive system
The digestive system is made up of the digestive tract—a series of hollow organs joined in a long, twisting tube from the mouth to the anus—and other organs that help the body break down and absorb food (see figure).
- Salivary Glands
- Pharotis
- Submandibularis
- Sublingualis
- Mouth
- Esophagus
- Pancreas
- Stomach
- Pancreas Tract
- Liver
- Gallbladder’s store
- duodenum
- Gallbladder’s tract
- Colon
- Colon transversum
- Colon ascenden
- Colon descenden
- Ileum
- Secum
- Appendix
- Rectum
- Anus
Organs that make up the digestive tract are the mouth, esophagus, stomach, small intestine, large intestine—also called the colon—rectum, and anus. Inside these hollow organs is a lining called the mucosa. In the mouth, stomach, and small intestine, the mucosa contains tiny glands that produce juices to help digest food. The digestive tract also contains a layer of smooth muscle that helps break down food and move it along the tract.
Two “solid” digestive organs, the liver and the pancreas, produce digestive juices that reach the intestine through small tubes called ducts. The gallbladder stores the liver’s digestive juices until they are needed in the intestine. Parts of the nervous and circulatory systems also play major roles in the digestive system.
II.2. The Principal Organs of Digestion
Digestive tract is a tubular passage of mucous membrane and muscle extending about 8.3 meters from mouth to anus; functions in digestion and elimination, a bodily passage or tube lined with epithelial cells and conveying a secretion or other substance. So it as the system that makes food absorbable into the body.
Stomach, tum, tummy, breadbasket are an enlarged and muscular saclike organs of the alimentary canal and the principal organ of digestion :
 pharynx , throat - the passage to the stomach and lungs; in the front part of the neck below the chin and above the collarbone large intestine - beginning with the cecum and ending with the rectum; includes the cecum and the colon and the rectum; extracts moisture from food residues which are later excreted as feces.
Ussually, a researcher is placing a large tube with a tiny internal camera through the mouth, pharynx, esophagus then stomach to see the forms of digestive tract from enteron to the stomach. But Dr. Camilleri use a painless teqhnique without tubes that can allows visualization of the stomach wall in order to measure its volume and motor responses—functions that are important determinants of how much a person can eat without feeling uncomfortable and, therefore, relevant to conditions such as obesity, anorexia nervosa, and dyspepsia (indigestion after eating).
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II.3. How food is digested
In his research, The technnique Dr. Camilleri takes by using external camera doesn’t need us to placing a large tube through our mouth. A radioactive substance that concentrates in the lining of the stomach is injected into the patient's veins. An external camera rotates around the abdomen, picks up the radioactive signal from the stomach and measures the surface area of "virtual" horizontal slices through the stomach. A computer program reconstructs the stomach in three dimensions and automatically measures its volume during fasting, after feeding, or after a medication is given.
According to me, we can see how food is digested directly during eating from both external or internal camera. External camera can give us an accurate result through the radioactive signal and an internal camera can give us a direct visualitation from inside the body. Eventhough so, radioactive has a possibility to damage our body and it’s too dangerous for our body for an internal camera to stay in stomach for a long duration. So, it’s has a risk to do this experiment to a human who still alive. To know about how food is digestive, here is the explanation :
Digestion involves mixing food with digestive juices, moving it through the digestive tract, and breaking down large molecules of food into smaller molecules. Digestion begins in the mouth, when you chew and swallow, and is completed in the small intestine.
1. Movement of Food Through the System
The large, hollow organs of the digestive tract contain a layer of muscle that enables their walls to move. The movement of organ walls can propel food and liquid through the system and also can mix the contents within each organ. Food moves from one organ to the next through muscle action called peristalsis. Peristalsis looks like an ocean wave traveling through the muscle. The muscle of the organ contracts to create a narrowing and then propels the narrowed portion slowly down the length of the organ. These waves of narrowing push the food and fluid in front of them through each hollow organ.
The first major muscle movement occurs when food or liquid is swallowed. Although you are able to start swallowing by choice, once the swallow begins, it becomes involuntary and proceeds under the control of the nerves.
Swallowed food is pushed into the esophagus, which connects the throat above with the stomach below. At the junction of the esophagus and stomach, there is a ringlike muscle, called the lower esophageal sphincter, closing the passage between the two organs. As food approaches the closed sphincter, the sphincter relaxes and allows the food to pass through to the stomach.
The stomach has three mechanical tasks.
i. First, it stores the swallowed food and liquid. To do this, the muscle of the upper part of the stomach relaxes to accept large volumes of swallowed material.
ii. The second job is to mix up the food, liquid, and digestive juice produced by the stomach. The lower part of the stomach mixes these materials by its muscle action.
iii. The third task of the stomach is to empty its contents slowly into the small intestine.
Several factors affect emptying of the stomach, including the kind of food and the degree of muscle action of the emptying stomach and the small intestine. Carbohydrates, for example, spend the least amount of time in the stomach, while protein stays in the stomach longer, and fats the longest. As the food dissolves into the juices from the pancreas, liver, and intestine, the contents of the intestine are mixed and pushed forward to allow further digestion.
Finally, the digested nutrients are absorbed through the intestinal walls and transported throughout the body. The waste products of this process include undigested parts of the food, known as fiber, and older cells that have been shed from the mucosa. These materials are pushed into the colon, where they remain until the feces are expelled by a bowel movement.
2. Production of Digestive Juices
The digestive glands that act first are in the mouth—the salivary glands. Saliva produced by these glands contains an enzyme that begins to digest the starch from food into smaller molecules. An enzyme is a substance that speeds up chemical reactions in the body.
The next set of digestive glands is in the stomach lining. They produce stomach acid and an enzyme that digests protein. A thick mucus layer coats the mucosa and helps keep the acidic digestive juice from dissolving the tissue of the stomach itself. In most people, the stomach mucosa is able to resist the juice, although food and other tissues of the body cannot.
After the stomach empties the food and juice mixture into the small intestine, the juices of two other digestive organs mix with the food. One of these organs, the pancreas, produces a juice that contains a wide array of enzymes to break down the carbohydrate, fat, and protein in food. Other enzymes that are active in the process come from glands in the wall of the intestine.
The second organ, the liver, produces yet another digestive juice—bile. Bile is stored between meals in the gallbladder. At mealtime, it is squeezed out of the gallbladder, through the bile ducts, and into the intestine to mix with the fat in food. The bile acids dissolve fat into the watery contents of the intestine, much like detergents that dissolve grease from a frying pan. After fat is dissolved, it is digested by enzymes from the pancreas and the lining of the intestine.
3. Absorption and Transport of Nutrients
Most digested molecules of food, as well as water and minerals, are absorbed through the small intestine. The mucosa of the small intestine contains many folds that are covered with tiny fingerlike projections called villi. In turn, the villi are covered with microscopic projections called microvilli. These structures create a vast surface area through which nutrients can be absorbed. Specialized cells allow absorbed materials to cross the mucosa into the blood, where they are carried off in the bloodstream to other parts of the body for storage or further chemical change. This part of the process varies with different types of nutrients.
Carbohydrates. The Dietary Guidelines for Americans 2005 recommend that 45 to 65 percent of total daily calories be from carbohydrates. Foods rich in carbohydrates include bread, potatoes, dried peas and beans, rice, pasta, fruits, and vegetables. Many of these foods contain both starch and fiber.
The digestible carbohydrates—starch and sugar—are broken into simpler molecules by enzymes in the saliva, in juice produced by the pancreas, and in the lining of the small intestine. Starch is digested in two steps. First, an enzyme in the saliva and pancreatic juice breaks the starch into molecules called maltose. Then an enzyme in the lining of the small intestine splits the maltose into glucose molecules that can be absorbed into the blood. Glucose is carried through the bloodstream to the liver, where it is stored or used to provide energy for the work of the body.
Sugars are digested in one step. An enzyme in the lining of the small intestine digests sucrose, also known as table sugar, into glucose and fructose, which are absorbed through the intestine into the blood. Milk contains another type of sugar, lactose, which is changed into absorbable molecules by another enzyme in the intestinal lining.
Fiber is undigestible and moves through the digestive tract without being broken down by enzymes. Many foods contain both soluble and insoluble fiber. Soluble fiber dissolves easily in water and takes on a soft, gel-like texture in the intestines. Insoluble fiber, on the other hand, passes essentially unchanged through the intestines.
Protein. Foods such as meat, eggs, and beans consist of giant molecules of protein that must be digested by enzymes before they can be used to build and repair body tissues. An enzyme in the juice of the stomach starts the digestion of swallowed protein. Then in the small intestine, several enzymes from the pancreatic juice and the lining of the intestine complete the breakdown of huge protein molecules into small molecules called amino acids. These small molecules can be absorbed through the small intestine into the blood and then be carried to all parts of the body to build the walls and other parts of cells.
Fats. Fat molecules are a rich source of energy for the body. The first step in digestion of a fat such as butter is to dissolve it into the watery content of the intestine. The bile acids produced by the liver dissolve fat into tiny droplets and allow pancreatic and intestinal enzymes to break the large fat molecules into smaller ones. Some of these small molecules are fatty acids and cholesterol. The bile acids combine with the fatty acids and cholesterol and help these molecules move into the cells of the mucosa. In these cells the small molecules are formed back into large ones, most of which pass into vessels called lymphatics near the intestine. These small vessels carry the reformed fat to the veins of the chest, and the blood carries the fat to storage depots in different parts of the body.
Vitamins. Another vital part of food that is absorbed through the small intestine are vitamins. The two types of vitamins are classified by the fluid in which they can be dissolved: water-soluble vitamins (all the B vitamins and vitamin C) and fat-soluble vitamins (vitamins A, D, E, and K). Fat-soluble vitamins are stored in the liver and fatty tissue of the body, whereas water-soluble vitamins are not easily stored and excess amounts are flushed out in the urine.
Water and salt. Most of the material absorbed through the small intestine is water in which salt is dissolved. The salt and water come from the food and liquid you swallow and the juices secreted by the many digestive glands.
II.4. How the digestive process is controlled1. Hormone Regulators
The major hormones that control the functions of the digestive system are produced and released by cells in the mucosa of the stomach and small intestine. These hormones are released into the blood of the digestive tract, travel back to the heart and through the arteries, and return to the digestive system where they stimulate digestive juices and cause organ movement.
The main hormones that control digestion are gastrin, secretin, and cholecystokinin (CCK):
Gastrin causes the stomach to produce an acid for dissolving and digesting some foods. Gastrin is also necessary for normal cell growth in the lining of the stomach, small intestine, and colon. Secretin causes the pancreas to send out a digestive juice that is rich in bicarbonate. The bicarbonate helps neutralize the acidic stomach contents as they enter the small intestine. Secretin also stimulates the stomach to produce pepsin, an enzyme that digests protein, and stimulates the liver to produce bile. CCK causes the pancreas to produce the enzymes of pancreatic juice, and causes the gallbladder to empty. It also promotes normal cell growth of the pancreas.
Additional hormones in the digestive system regulate appetite:
Ghrelin is produced in the stomach and upper intestine in the absence of food in the digestive system and stimulates appetite. Peptide YY is produced in the digestive tract in response to a meal in the system and inhibits appetite.
Both of these hormones work on the brain to help regulate the intake of food for energy. Researchers are studying other hormones that may play a part in inhibiting appetite, including glucagon-like peptide-1 (GPL-1), oxyntomodulin (+ ), and pancreatic polypeptide.
2. Nerve Regulators
Dr. Camilleri Studying how the adrenergic nervous system controls the GI system and learning ways to manipulate specific mechanisms that can relieve patient symptoms such as diarrhea, constipation, pain, and indigestion after eating.
There are two types of nerves help control the action of the digestive system.
- Extrinsic, or outside, nerves come to the digestive organs from the brain or the spinal cord. They release two chemicals, acetylcholine and adrenaline. Acetylcholine causes the muscle layer of the digestive organs to squeeze with more force and increase the “push” of food and juice through the digestive tract. It also causes the stomach and pancreas to produce more digestive juice. Adrenaline has the opposite effect. It relaxes the muscle of the stomach and intestine and decreases the flow of blood to these organs, slowing or stopping digestion. So, if the production of acetylcholine is increase, there will be to much digestive juice that can disturb the digestive system that can causes vomit or diarrhea. On the contrary, if adrenaline is decrease it also decreases the flow of blood to principal organs of digestive system, it makes pain and constipation.
- The intrinsic, or inside, nerves make up a very dense network embedded in the walls of the esophagus, stomach, small intestine, and colon. The intrinsic nerves are triggered to act when the walls of the hollow organs are stretched by food. They release many different substances that speed up or delay the movement of food and the production of juices by the digestive organs. If there is disbalance in the intrinsic nerves, it can be the reason of the diseases of digestive system.
II.5. The Advantage Of Digestive System
When you eat foods—such as bread, meat, and vegetables—they are not in a form that the body can use as nourishment. Food and drink must be changed into smaller molecules of nutrients before they can be absorbed into the blood and carried to cells throughout the body. Digestion is the process by which food and drink are broken down into their smallest parts so the body can use them to build and nourish cells and to provide energy.
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II.6.. The diseases in the digestive system
Digestive diseases are all diseases that happen to digestive track. These diseases are the common group of diseases in esophagus; stomach; the first, second and third duodenum; jejunum; ileum; colon; colon sigmoid and rectum.
Symptoms caused by disorder gastrointestinal function like Dr. Camilleri’s said such as constipation, diarrhea, and cramping, are the second leading cause for absenteeism in the workplace. He works to research Intestinal Bowel Syndromes that devide into :
1. Intestinal Bowel Syndrome-Diarrhea
Diarhea happens because of the hiperstimulating in the intestinal mucosa so that the peristaltic move increases and food is not absorbed perfectly. Diarrhea is the most always occurs disease, specially to children.
Accute diarrhea is named to it if diarrhea occurs more than 4 times a day. The reason can be infection or even just the wrong food. For example, an appropriate food with child’s age; given solid food not intime yet. Diarrhea can also caused by unhygienity. Diarrhea caused by germs is the main reason of digestive disease to children under 5 years. There is also diare caused by worms.
From Dr. Camilleri’s research, After lengthy multi-center clinical trials, the Food and Drug Administration (FDA) approved Alosetron (Lotronex®).
Alosetron is indicated for women with severe diarrhea-predominant irritable bowel syndrome who have : chronic irritable bowel syndrome symptoms (generally lasting 6 months or longer), had anatomic or biochemical abnormalities of the gastrointestinal tract excluded, and not responded adequately to conventional therapy.
Diarrhea-predominant irritable bowel syndrome is severe if it includes diarrhea and one or more of frequent and severe abdominal pain/discomfort, frequent bowel urgency or fecal incontinence, disability or restriction of daily activities due to irritable bowel syndrome.
Because of infrequent but serious gastrointestinal adverse events associated with Lotronex, the indication is restricted to those patients for whom the benefit-to-risk balance is most favorable. Clinical studies have not been performed to adequately confirm the benefits oh Lotronex in men.
2. Intestinal Bowel Syndrome-Constipation
Constipation is an aberration in the digestive system wih the indication feces harder and difficult to let it out through anus that make us in pain. Constipation caused by what and how we eat, hormones, side effects of drugs and anatomic aberration.
Great constipation is called obstipation. The digestive disease is also caused by stress because it can be influential to the nerv system.
Tegaserod (Zelnorm®) is an oral medication for treatment of constipation ad constipation predominant irritable bowel syndrome (IBS) in women. IBS is a chronic gastrointestinal disorder characterized by recurrent abdominal pain or discomfort and altered bowel function which either constipation or dhiarrea. As many as 20% of American adults suffer from IBS. Contractions of intestinal muscles, primarily those of the colon, control the movement of food through the intestine.
In constipated patients, there are fewer contractions than in persons without constipation. An important factor that controls the contraction is seroronin. Seroronin is a chemical manufactured by nerves in the intestine. It is released by the nerves and the travels and binds to receptors on the surface of earby nerves. It is a “neurotransmitter”, a chemical messenger, that is, a chemical that nerves use to communicate with each other. When it binds to receptors on the nerves that control contractions of the intestinal muscles, serotonin can either promote or prevent contractions depending on the type of receptors it binds to. Binding to some types of receptors causes contractions, and binding to some types of receptors causes contractions, and binding to other types of receptors blocks contractions.
The serotonin 5-HT4 receeptor is a receptor that prevents serotonin from binding o it. As a result, contractions increase. The increased cantractions speed the transit of digesting food and reverse the constipation. In addition, tegaserod reduces the sensitivity of the intestinal pain-sensing nerves and can thereby reduce the perception of pain. Tegaserod was approved also by FDA.
III. END
III.1. Conclusion
From the contents of this working paper, we can take conclusion that together, nerves, hormones, the blood and the organs of the digestive system conduct the complex tasks of digesting and absorbing nutrients from the foods and liquids we consume each day.
III.2. Suggestion
The digesive system in human’s body is very important in the metabolism of food and water into energy which we use in our daily activities. So, as good people who love ourselves we have to take care in our digestive system by consume health food and drink enough water to fluent the metabolism and get enough energy we need.
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