nutr NUTR 120
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Eudijessica Melo de Oliveira
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This 7 page Class Notes was uploaded by Dinha on Saturday November 14, 2015. The Class Notes belongs to NUTR 120 at University of New Mexico taught by a professor in Fall 2015. Since its upload, it has received 43 views. For similar materials see Nutrition for Health in Nutrition and Food Sciences at University of New Mexico.
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Date Created: 11/14/15
Chapter 3 The human body: are we really what we eat? Two mechanisms prompt us to seek food: Hunger and Appetite. Hunger is a physiologic drive for food that occurs when the body senses that we need to eat. Nonspecific. Appetite is a psychological desire to consume specific foods. Anorexia is an absence of appetite. The brain tells us when we are hungry. The region of brain tissue that is responsible for prompting us to seek food is called the hypothalamus. The hypo thalamus triggers feelings of hunger or satiation (fullness) by integrating signals from nerve cells in other body regions and from chemical messengers called hormones. Hormones are chemical messengers that are secreted into the bloodstream by one of the many endocrine glands of the body. Insulin and glucagon are two hormones produced in the pancreas. They are responsible for maintaining blood glucose levels. Glucose is our bodies’ most readily available fuel supply. * Appetite is triggered by aspects of our environment. Food and Satiety • Proteins have the highest satiety value • Fats have a higher satiety value than carbohydrates • Fiber and water distend the stomach and promote a sense of satiety • Solid foods are more filling than semisolid foods or liquids The Gastrointestinal Tract: Upper GI Mouth, esophagus, and stomach Lower GI Small Intestine and Large intestine Support Systems Liver, gallbladder, and pancreas What happens to the food we eat? When we eat, the food we consume is digested, then the useful nutrients are absorbed, and, finally, the waste products are eliminated. Digestion is the process by which foods are broken down into their component molecules, either mechanically or chemically. Absorption is the process of taking these products of digestion through the wall of the intestine. Elimination is the process by which the undigested portions of food and waste products are removed from the body. The processes of digestion, absorption, and elimination occur in the Gastrointestinal (GI) tract that is long, muscular tube consisting of several organs: the mouth, esophagus, stomach, small intestine, and large intestine. DIGESTION Cephalic phase: In this phase hanger and appetite work together to prepare the GI to digest food. • Oral phase: Mouth and Esophagus Role of the mouth: Mechanical: Chewing (tongue, teeth) Chemical: Saliva (enzymes, lubrication, antibiotic & Lysozome action, bicarbonate); Salivary amylase – starch digestion. Saliva is secreted from the salivary glands. Five distinct tastes: bitter, sweet, salty, sour, and umami. Enzymes are complex chemicals, usually proteins that induce chemical changes in other substances to speed up bodily processes. Bolus: isthe mass of food that has been chewed and moistened in the mouth. Peristalsis: rhythmic waves of squeezing and pushing contractions that move food, chime, and feces in one direction through the length of GI tract. Hydrochloric acid: is secreted by parietal cells and keeps the stomach interior very acid. It iextremely important for digestion because it starts to denature proteins. Chyme: a semifluid mass consisting of partially digested food, water, and gastric juices. Small intestine: is the longest portion of the GI tract, accounting for about two thirds of its length. It is composed of three sections: duodenum, jejunum, and ileocecal valve. Most digestion and absorption take place in the small intestine. Bile from the gallbladder emulsifies fat to aid digestion. Insulin and glucagon are two hormones produced in the pancreas. They are responsible for maintaining blood glucose levels. Glucose is our bodies’ most readily avail able fuel supply. It’s not surprising, then, that its level in our blood is an important signal regulating hunger. When we have not eaten for a while, our blood glucose levels fall, prompting a change in the level of insulin and glucagon. Gallbladder stores bile. And bile emulsifies the lipids. Liver: processes and stores many nutrients. This organ also makes cholesterol and uses this lipid to make bile, a substance that prepares fat and fatsoluble vitamins for absorption. Hydrolysis: is a chemical reaction that breaks down substances by the addition of water. Pancreas: produces and secretes most of the enzymes that break down carbohydrates, protein, and fat in the GI tract. Additionally, the pancreas secretes bicarbonate ions (HCO ) th3t neutralize HCl in chyme when it enters the duodenum. Enzymes secreted by the pancreas include pancreatic amylase, which continues the digestion of carbohydrates, and pancreatic lipase, which continues the digestion of lipids. Bicarbonate secreted by the pancreas neutralizesacidic chyme coming from the stomach into the small intestine. Passive diffusion: is the simple absorptive process in which nutrients pass through the enterocytes and into the bloodstream without the use of a carrier protein or the requirement of energy. Facilitated diffusion: is the absorptive process that occurs when nutrients are shuttled across the enterocytes with the help of a carrier protein. Active transport: an absorptive process that requires the use of energy to transport nutrients and other sub stances in combination with a carrier protein. Endocytosis: an absorptive process by which a small amount of the intestinal contents is engulfed by the cell membrane (also called pinocytosis). Large Intestine: the final organ of the GI tract of the cecum, colon, rectum, and anal canal and in which most water is absorbed and feces are formed. Occurs the absorption of: water, short chain fatty acids, oligosaccharides, electrolytes, and vitamin K. Transport of nutrients and wastes: Blood: travels to all of our tissues to deliver nutrients and other materials and to pick up waste products. Lymph travels through the lymphatic system and transports most lipids and fat soluble vitamins. Lacteals pick up most lipids and fatsoluble vitamins Lymph nodes are clusters of immune cells that filter microbes and other harmful agents DIGESTIVE DISORDERS Belching and Flatulence The primary cause of belching is swallowed air. Eating too fast, wearing improperly fitting dentures, chewing gum, sucking on hard candies or a drinking straw, and gulping food or fluid can increase the risk of swallowing air. Flatus (Intestinal gasesis a mixture of many gases, including nitrogen, hydrogen, oxygen, methane, and carbon dioxide. Foods most commonly reported to cause flatus include those rich in fibers, starches, and sugars, such as beans, dairy products, and some vegetables. The partially digested carbohydrates from these foods pass into the large intestine, where they are acted upon by bacteria, producing gas. Heartburn Is the painful sensation that occurs over the sternum when hydrochloric acid backs up into the lower esophagus. Gastroesophageal reflux disease (GERD) Is a more painful type of heartburn that occurs more than twice per week. Causes: hiatal hernia, cigarette smoking or alcohol use, being overweight, pregnancy, chocolate, citrus, spicy or fried food, large highfat meal, and lying down soon after meal. Peptic Ulcers Is an area of the GI tract that has been eroded away by a combination of hydrochloric acid and the enzyme pepsin. It causes a burning pain in the abdominal area, typically 1 to 3 hours after eating a meal. In serious cases, eroded blood vessels bleed into the GI tract, causing vomiting of blood and/or blood in the stools, as well as anemia. The bacterium Helicobacter pylori (H. pylori) plays a key role in development of most peptic ulcers, which include both gastric and duodenal ulcers. And because of the role of H. pylori in ulcer development, treatment usually involves antibiotics and other types of medications to reduce gastric secretions. Antacids are used to weaken the gastric acid, and the same medications used to treat GERD can be used to treat peptic ulcers. Food intolerance Is a cluster of GI symptoms (often gas, pain, and diarrhea) that occur following consumption of a particular food. The immune system plays no role in intolerance, and although episodes are unpleasant, they are usually transient, resolving after the offending food has been eliminated from the body. Food allergy Is a hypersensitivity reaction of the immune system to a particular component (usually a protein) in a food. This reaction causes the immune cells to release chemicals that cause either limited or systemic (wholebody) inflammation. About 5% of infants and young children and 2% of adults experience food allergies. Celiac disease Is a digestive disease that severely damages the lining of the small intestine and interferes with absorption of nutrients. As in food allergy, the body’s immune system causes the disorder. However, there is a strong genetic predisposition to celiac disease, with the risk now linked to specific gene markers. In celiac disease, the offending food component is gliadin, a fraction of a protein called gluten that is found in wheat, rye, and barley. If the person is unaware of the disorder and continues to eat gluten, repeated immune reactions cause the villi to become greatly decreased so that there is less absorptive surface area. In addition, the enzymes located at the brush border of the small intestine become reduced Crohn’s Disease Is an autoimmune disorder, a condition in which the body’s immune system does not function properly and begins to attack normal cells. Symptoms: diarrhea, abdominal pain, rectal bleeding, weight loss, fever, and anemia. Diarrhea Is a condition characterized by frequent, loose bowel movements. Diarrhea occurs when more water than normal is secreted into the GI tract or the tract absorbs less water than nor mal. Most cases of diarrhea result from bacterial or viral infections of the intestinal tract. The infectious bacteria or viruses produce irritating or toxic substances that increase the movements (motility) of the GI tract. As a result, the GI tract propels chyme more rapidly through it, absorbing less water than nor mal in the process. Increased GI motility also enables the large intestine to eliminate the watery feces and the toxic material it contains rapidly. Constipation Many factors influence the frequency of bowel movements. Lack of dietary fiber; low water intake; anxiety, depression, and other psychological disturbances; and changes in your typical routine, such as taking a long trip or having major surgery, can alter your usual pattern of bowel movements. Ulcerative colitis Inflammation and ulceration of colon mucosa Immune response to a virus or bacteria. Symptoms similar to Crohn's disease Not caused by food Foods may cause GI discomfort Irritable Bowel Syndrome Is a condition characterized by intestinal cramps and abnormal bowel function, particularly diarrhea, constipation, or alternating episodes of both. 11Loose stools are often accompanied with mucus, and after bowel movements, the affected person feels as though elimination of stools was in complete. For reasons that are unknown, women are more likely than men to suffer from IBS.
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