Table of Contents: Food and Nutrition I. Introduction II. Overview of Digestion A. Processes of the Digestive Process 1. Ingestion 2. Digestion 3. Movement 4. Absorption 5. Elimination B. Cellular Metabolism and Respiration III. Gastrointestinal Tract A. The Mouth B. The Pharynx and Esophagus C. The Stomach and Small Intestine 1. Stomach 2. Small Intestine a. obesity: type II diabetes and cardiovascular disease D. The Pancreas, Liver, and Gall Bladder E. The Large Intestine IV. Nutrition A. Nutrients 1. Carbohydrates 2. Proteins 3. Lipids 4. Minerals 5. Vitamins a. fat-soluble b. water-soluble B. Nutritious Meals 1. People Decide What to Eat 2. Healthy Diet V. Conclusion |
The gastrointestinal tract consists of several organs. The first is the mouth, where the food is placed. The mouth begins to mechanically break down the food by chewing it with the teeth as the tongue moves it around. Chemical digestion is also occurring, as the tongue's taste buds activate nerve impulses to the brain to release enzymes, like salivary amylase, from the salivary glands. Then, the food is formed into a small ball, called a bolus, to be passed to the pharynx and esophagus. The pharynx is a cavity located behind the mouth and nasal passages where food (and air) passes. As people swallow food, the pharynx is shut off, in order for the food to travel into the esophagus without getting caught in the glottis, or voice box. The esophagus moves the food by peristalsis to a valve, called the lower gastroesophageal sphincter, that is placed over the entrance to the stomach. Then, the stomach opens the valve and allows the food to enter. The stomach, "...stores food, initiates the digestion of protein, and controls the movement of chyme (partly digested food) into the small intestine" (Mader 148). It has three layers of muscle that contain deep pockets, called rugae, that contain gastric glands. The gastric glands produce gastric juice that contains the enzyme, pepsin, and hydrochloric acid that help breakdown proteins and kills any bacteria that is with the food. After the stomach has finished its process, peristalsis moves the food toward the end valve in the stomach, called the pyloric sphincter, where the food is released, a small amount at a time, into the small intestine. The small intestine is the main organ where the nutrients, carbohydrates, proteins, and lipids from the food, are finally digested and absorbed. It is inside the walls of the small intestine where enzymes are released such as, maltase (carbohydrate), peptidases (protein), and nucleosidases (nucleic acid), and starch is digested into glucose, protein is digested into amino acids, and lipids are digested into fatty acids. Also, the walls contain micro-hairs called, villi, where the food is absorbed into the blood capillaries. But, if too much of a nutrient is digested and absorbed by the small intestine, it can lead to obesity, which causes particular disorders like, type II diabetes and cardiovascular disease. Type II diabetes happens when, "...long time exposure to simple carbohydrates...reduce(s) the body's normal response to insulin, presumably because insulin is...in high concentrations in the blood" (highered.mcgraw-hill.com). Then the small intestine can not absorb the needed glucose energy for the cells. And cardiovascular disease occurs when too many fatty acid molecules are released into the small intestine and create plaque in the arteries. Along with the digestion of food in the small intestine, the pancreas, liver, and gall bladder also assist with this process. Located behind the stomach, the pancreas releases pancreatic juice into the top portion of the small intestine through the pancreatic duct. The pancreatic juice contains, "...sodium bicarbonate...(that) neutralizes acid chyme from the stomach" (Mader 152) and the enzymes, pancreatic amalyse, trypsin, and lipase, to digest starch, protein, and fat. It also releases the hormone insulin, that stimulates cells to use the broken down glucose for quick energy in cellular metabolism or store it as glycogen in the liver. The liver, along with storing glucose as glycogen, detoxifies the blood, stores fat soluble vitamins, makes urea (waste product) after digesting amino acids, and regulates cholesterol in the blood by producing bile salts. The bile salts are derived from the bile that is stored in the gallbladder by the common hepatic duct. The gall bladder also sends bile to the top portion of the small intestine, by the common bile duct, to emulsify the fats being digested. The last organ is the large intestine, where water, bacteria, dietary fiber, and other indigestible materials are made into feces. Then, peristalsis moves the feces to the rectum until it is ready to be expelled by the anus. The food that is digested by the gastrointestinal tract consists of an entire realm itself of nutrition. Figure 1: The gastrointestinal tract: mouth, pharynx, esophagus, stomach, small intestine, pancreas, liver, gall bladder, and large intestine.
Nutrition is composed of nutrients and nutritious meals. Nutrients are, "...a component of food that performs a physiological function in the body...providing us with energy, promote growth and development, and regulate cellular metabolism" (Mader 158). There are macro nutrients, which are carbohydrates, proteins, and lipids, and micro nutrients, which are minerals and vitamins. Carbohydrates are the most needed source of energy for the body. They can either be made of a single glucose molecules or many glucose molecules, which are termed simple complex carbohydrates. In reference to food, anything made from refined carbohydrates are not necessary for body functions and should be minimized in any diet. For example, mostly all processed foods, such as white breads, sugary breakfast cereals, cookies, crackers, etc., are striped of any essential carbohydrates during the manufacturing process, which could be harmful in the long run. Instead, complex carbohydrates, like whole grains, beans, fruits, vegetables, and nuts, provide the body with appropriate vitamins, minerals, and fiber. Figure 2: An example of a good sources of complex carbohydrates: whole grains, fruits, vegetables, beans, and nuts.
Proteins, "...are needed to supply the essential amino acids" (Mader 159). There are 20 different kinds of amino acids, but there are eight of them that are needed externally by diet and need to be replenished everyday. They can be found in foods such as, eggs, dairy products, meats, and legumes. But, over consumption of proteins can cause dehydration, from the excess amino acids being excreted in wastes, and kidney stones, due to calcium loss inwastes. Figure 3: An example of good sources of protein: eggs, meats, and legumes. Lipids can either be saturated or unsaturated. Saturated fats usually come from foods that are animal products like, meats and butter. This type of fat has been found to cause cardiovascular disease when consumed in large quantities. Unsaturated fats are usually components of oils. And is made of monounsaturated and/or polyunsaturated fats. This type of fat has been found to promote cardiovascular health from the essential fatty acids of omega three's and omega six's. Also, lipids are also composed of cholesterol, which is also recommend to be eaten in moderation due to increase risk of cardiovascular disease. The micro nutrients contain that of minerals and vitamins. Minerals contain the categories of major minerals and trace minerals. The major minerals, such as calcium, phosphorus, potassium, sulfur, sodium, chloride, and magnesium, are, "...constituents of cells and body fluids and are structural components of tissues" (Mader 160). For example, calcium aids in the production of strong bones, nerve conduction, and muscle contraction. But, if too little or too much of calcium is present in the body, it can lead to stunted growth and low bone density or kidney stones. The trace minerals, such as zinc, iron, copper, iodine, selenium, and maganese, are, "...parts of larger molecules..." (Mader 160). For example, iron is found in hemoglobin and aids in hemoglobin synthesis. But, if too little or too much of iron is present in the hemoglobin, it can cause anemia or organ failure and death. Another micro nutrient, vitamins, are, "...organic compounds...that the body uses for metabolic purposes but is unable to produce in adequate quantity" (Mader 162). Vitamins can be separated into two different kinds. The first is fat-soluble vitamins that consist of A, D, E, and K. These type of vitamins are broken down by lipids within the body and can usually be found in dairy products, nuts, fruits, and vegetables. But, certain disorders can arise if too much or too little of each vitamin is present. The second type is water-soluble vitamins that consist of C, niacin, folic acid, pantothenic acid, biotin, and the B's. These are broken down by water molecules in the body and can usually be found in fruits, beans, nuts, dairy products, meat products, and vegetables. But, certain disorders can also happen if each is not taken within the recommended limits. In order to apply these nutrients to the human body, it is important to consume nutritious meals.
The drive to consume nutritious meals is based upon what people decide to eat, which is usually culturally influenced. But, in the United States, people are deciding what to eat by commercial influence and it's creating false, healthy advertising that is actually pure junk food. People in the U.S. are also eating more packaged and processed foods instead of creating optimal meals from fresh and real ingredients. For example, Michael Pollan states, "...it's...alot easier to slap a health claim on a box of sugary cereal than on a potato or carrot, with the perverse result that the most healthful foods in the supermarket sit there quietly in the produce section...while a few aisles over, the Coco Puffs and Lucky Charms are screaming about their new found whole-grain goodness" (http://www.nytimes.com/). In order to provide the body with a healthy diet, food should be viewed from a standard of positive solutions. For example, it can be the rebirth of a cultural and soulful influence back into the foods that people eat, which will provide long term health to humans, farming, and the entire biosphere. And it can consist of local, home-cooked, non-packaged, spiritually satiating foods.
The gastrointestinal tract is an amazing system that carries out several processes in order for the body to function correctly. It begins with the overview of digestion where food is ingested, digested, moved, absorbed, and eliminated throughout many different organs in the body. The different organs that help carry out the processes of the GI tract is the mouth, where food is mechanically and chemically digested; the pharynx and esophagus, where the food is collected and moved by peristalsis; the stomach and small intestine, where food is broken down into chyme by gastric juices and is digested and absorbed; the pancreas, liver and gall bladder, where digestion is assisted in the small intestine by ways of enzymes, storing energy, and emulsifying fats; and the large intestine, where unnecessary materials are excreted. The GI tract also needs the importance of nutrition from particular nutrients. They consist of carbohydrates, proteins, lipids, minerals, and vitamins that properly carry out such processes. And lastly, nutritious meals need to be provided for the body by means of fresh, real, and spiritually satisfying foods. The body can survive for two weeks without any food before completely failing. But, the body contains many tools, such as the gastrointestinal tract, that, if treated properly, can provide a happy and healthful life to each individual.
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Pictures:
1. human.freescience.org/images/wikimages/433px...
2. t3.pacific.edu/teams/M00735/carbohydrates.jpgWorks:1. Human Biology 10e. Mader, Sylvia S.2. en.wikipedia.org3. highered.mcgraw-hill.com/classware/ala.do?alaid=ala_1013264
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