Unformatted text preview: Chapter 3‐ Review Outline Learning Objectives After completing Chapter 3, the student will be able to: 1. List the segments of the digestive tract in order from the mouth to the colon. 2. Explain the mechanical processes of digestion in order of occurrence in the digestive tract. 3. List the five organs and their secretions which assist in the breakdown of food. 4. List the secretions that break down carbohydrates. 5. List the secretions that break down protein. 6. List the secretions that break down fat. 7. Describe the anatomy of the absorptive system. 8. Explain the role of the circulatory system and the lymphatic system in transport of nutrients. 9. Identify the hormones involved in digestive and absorptive processes. 10. Apply the concepts presented in the chapter to explain common digestive tract problems. I. Digestion Digestion is the process of breaking down foods into nutrients to prepare for absorption while overcoming 7 challenges. A. Anatomy of the Digestive Tract – The gastrointestinal (GI) tract is the flexible muscular tube from mouth to anus. The lumen is the inner space of the tract. 1. The mouth is the beginning of the digestive system. Digestion in the mouth involves mastication (chewing), the stimulation of taste buds, and swallowing. The epiglottis closes to prevent food from entering the pharynx. After swallowing the food is called a bolus. 2. The esophagus is the tube that leads the bolus to the stomach. There is a sphincter at the upper and lower (also known as the cardiac sphincter) ends of the esophagus. 3. The stomach adds juices and grinds the bolus to a semiliquid mass called chyme. The pyloric sphincter regulates the flow of partially digested food into the small intestine. 4. The small intestine receives digestive juices from the gallbladder and the pancreas. The three segments of the small intestine are the duodenum, the jejunum and the ileum. 5. The large intestine (colon) begins at the ileocecal valve and ends at the rectum and anus. The chyme passes by the opening of the appendix. B. The Muscular Action of Digestion – under autonomic control 1. Peristalsis pushes the digestive contents along. 2. Stomach action involves circular, longitudinal, and diagonal muscles. 3. Segmentation is contractions by circular muscles that contract and squeeze contents to promote mixing with digestive juices. 4. Sphincter contractions open and close passageways. This prevents reflux and controls the passage of contents. C. The Secretions of Digestion 1. Includes digestive enzymes that act as catalysts in hydrolysis reactions 2. Saliva from the salivary glands moistens foods 3. Gastric juice from the gastric glands includes hydrochloric acid. The goblet cells of the stomach wall secrete mucus to protect the walls of the stomach from the high acidity levels that are measured by pH units. 4. Pancreatic juice contains intestinal enzymes (carbohydrase, lipase, protease) and bicarbonate. 5. Bile is produced by the liver, stored in the gall bladder, and acts as an emulsifier to suspend fat. HUN2201‐ Nutrition Anatomy (Chapter 3)‐ Study Outline 2 D. The Final Stage 1. Energy‐yielding nutrients are disassembled for absorption. 2. Vitamins, minerals and water can be absorbed. 3. Undigested residues, including some fibers, continue through the digestive tract and form stool. 4. Recycling of usable materials II. Absorption The enormous surface area of the small intestine facilitates nutrient absorption. Nutrients can be absorbed through simple diffusion, facilitated diffusion, or active transport. A. Anatomy of the Absorptive System 1. Villi are the fingerlike projections within the folds of the small intestine that move in a wave‐like pattern to trap nutrients. 2. Microvilli are the microscopic hairlike projections on each villi. 3. Crypts are the tubular glands that lie between the intestinal villi. 4. Goblet cells are located between the villi and secrete a protective thick mucus. B. A Closer Look at the Intestinal Cells 1. Specialization of the cells to absorb different nutrients 2. “Food combining” which emphasizes separating food for digestive purposes is a myth. 3. Preparing Nutrients for Transport a. Water‐soluble nutrients and small products of fat digestion are released to the bloodstream. b. Fat‐soluble vitamins and larger fats form chylomicrons and are released to the lymphatic system. III. The Circulatory System Water‐soluble nutrients and small fats are routed to the liver before being transported to the cells. Fat‐soluble nutrients, entering from the lymph, bypass the liver at first and eventually enter the vascular system. A. The vascular system consists of arteries, capillaries and veins. 1. The hepatic portal vein directs blood from the GI tract to the liver. 2. The hepatic vein takes blood from the liver to the heart. 3. The liver protects against toxic substances. B. The lymphatic system consists of one‐way vessels to transport fluid. 1. Lymph is a clear, yellowish fluid without red blood cells or platelets that moves through the body by muscle contractions. 2. The thoracic duct is the lymph’s route to the heart. 3. The subclavian vein provides a return of lymph to the vascular system. 4. Lacteals are the lymphatic vessels of the intestine that absorb nutrients and pass them to the lymphatic system. IV. The Health and Regulation of the GI Tract The principle of homeostasis is important in the functioning of the digestive and absorptive systems. The body’s hormonal and nervous control systems keep conditions normal. A. Gastrointestinal Bacteria 1. A healthy GI tract has many different non‐disease‐causing bacteria known as flora or microflora. 2. Probiotics are bacteria found in the GI tract that can be beneficial to health. An example is the bacteria found in yogurt. HUN2201‐ Nutrition Anatomy (Chapter 3)‐ Study Outline 3 3. Prebiotics are foods that are used as food by intestinal bacteria. B. Gastrointestinal Hormones and Nerve Pathways 1. Hormones act as messengers, and those involved in the GI tract are known as enterogastrones. 2. Gastrin is secreted by the stomach. 3. Pyloric sphincter 4. Secretin is secreted by the duodenum. 5. Pancreatic secretions change based on the content of the diet. 6. The pancreas is protected against enzymes by creating enzyme precursors called proenzymes or zymogen. 7. Cholecystokinin targets the gall bladder. 8. Motility slows for foods that take longer to be digested. C. The System at Its Best 1. A healthy digestive tract is essential. 2. Balance, moderation, variety and adequacy of meals are important. V. Common Digestive Problems Many digestive problems reflect hurried lifestyles. Remedies include handling stress, relaxing, getting enough sleep, and eating in a leisurely manner, in addition to diet strategies. A. Choking 1. Food becomes lodged in the trachea. 2. The larnyx cannot make sounds. 3. The Heimlich maneuver may need to be used. 4. Strategies a. Small bites b. Chew thoroughly. c. Don’t talk or laugh with food in the mouth. d. Don’t eat when breathing hard. B. Vomiting 1. Body’s adaptive mechanism 2. Dehydration is a concern. 3. May be self‐induced as in eating disorders C. Diarrhea 1. Frequent, loose, watery stools 2. Irritable bowel syndrome or colitis is one of the common GI disorders. 3. Strategies a. Rest b. Drink fluids c. Medical help is needed if it persists. D. Constipation 1. Defecation habits are different among people. 2. Many causes are possible. 3. Hemorrhoids may be a problem. 4. Diverticulosis is a condition in which the intestinal walls weaken and bulge. The bulging pockets are called diverticula. Diverticulitis is a worsened condition and requires intervention. 5. Use of laxatives, enemas and mineral oil may not be necessary with lifestyle changes. 6. Colonic irrigation is the internal washing of the large intestine and can be hazardous. HUN2201‐ Nutrition Anatomy (Chapter 3)‐ Study Outline 4 7. Strategies a. High‐fiber diet b. Increased fluids c. Exercise regularly. d. Respond quickly to the urge to defecate. E. F. G. Belching and Gas 1. Strategies a. Eat slowly. b. Chew thoroughly. c. Relax while eating. d. Watch bothersome foods. 2. Hiccups are triggered by eating or drinking too fast. Heartburn and “Acid Indigestion” 1. Gastroesophageal reflux is the backward flow of stomach contents into the esophagus. 2. Antacids and acid controllers may help indigestion. 3. Strategies a. Small meals b. Liquids between meals c. Sit up while eating. d. Wait 1 hour after eating before lying down. e. Wait 2 hours after eating before exercising. f. Refrain from tight‐fitting clothing. g. Avoid bothersome foods. h. Refrain from tobacco use. i. Lose weight if overweight. Ulcers 1. Peptic ulcers can be gastric or duodenal. 2. Strategies a. Take prescribed medicine. b. Avoid caffeine‐ and alcohol‐containing foods. c. Minimize aspirin and ibuprofen use. d. No smoking. HUN2201‐ Nutrition Anatomy (Chapter 3)‐ Study Outline 5 Q & As for Discussion 1. Describe the obstacles associated with digesting food and the solutions offered by the human body. The epiglottis closes off the airways so that food and liquid do not enter the lungs. Food passes through the diaphragm to reach the stomach by way of the esophagus. Fluids are added to the food as it travels through the system allowing smooth passage. Water is reabsorbed in the large colon, thus conserving water and creating a semisolid waste. Peristalsis keeps the materials steadily moving through the system and sphincter muscles serve as one‐way gates allowing small quantities to pass at appropriate intervals. Stomach cells secrete mucus to protect them from acid and enzymes that would digest them. Rectal muscles prevent elimination until voluntarily performed. 2. Describe the path food follows as it travels through the digestive system. Summarize the muscular actions that take place along the way. Food enters the mouth and travels past the epiglottis, down the esophagus and through the cardiac sphincter to the stomach, then through the pyloric sphincter to the small intestine, on through the ileocecal valve to the large intestine, past the appendix to the rectum, ending at the anus. Muscular actions include: chewing, swallowing, peristalsis, segmentation, and sphincter contractions. 3. Name five organs that secrete digestive juices. How do the juices and enzymes facilitate digestion? Salivary glands, stomach glands, pancreas, liver, gallbladder, and intestinal glands. Salivary glands secrete saliva that contains amylase enzyme that breaks down starch. Gastric juice is secreted by the cells in the stomach wall and contains pepsin and HCl that break down proteins. Pancreatic juice contains bicarbonate that neutralizes acidic gastric juices as well as other enzymes that break down CHO, protein and fat. The gallbladder secretes bile which emulsifies fat. 4. Describe the problems involved with absorbing nutrients and the solutions offered by the small intestine. The body must find a way to absorb many molecules. It solves this by its anatomy—the small intestine has hundreds of folds, each covered with thousands of villi, which in turn are composed of hundreds of cells, which in turn are covered with microvilli, providing a very large surface area for nutrient molecules to make contact and be absorbed. 5. How is blood routed through the digestive system? Which nutrients enter the bloodstream directly? Which are first absorbed into the lymph? Heart to arteries to capillaries (in intestines) to vein to capillaries (in liver) to vein to heart. Water‐soluble nutrients and small products of fat digestion enter the bloodstream directly; large fats and fat‐soluble nutrients are first absorbed into the lymph. 6. Describe how the body coordinates and regulates the processes of digestion and absorption. The body’s hormonal system and nervous system coordinate all the digestive and absorptive processes. The contents in the GI tract either stimulate or inhibit digestive secretions by way of messages that are carried from one section of the GI tract to another by both hormones and nerve pathways. 7. How does the composition of the diet influence the functioning of the GI tract? Enzyme activity changes proportionately in response to the amounts of carbohydrate, fat and protein in the diet. Hormones in the GI tract inform the pancreas as to the amount and type of enzymes to secrete in response to diet; the presence of fat slows GI motility. 8. What steps can you take to help your GI tract function at its best? Obtain adequate sleep, engage in physical activity, keep a positive state of mind, and eat meals with these characteristics: balance, moderation, variety, and adequacy. HUN2201‐ Nutrition Anatomy (Chapter 3)‐ Study Outline 6 Chapter 3 Crossword Puzzle 1 2
3 5 4 6 7 8 9 10 Across 3. the food pipe; the conduit from the mouth to the stomach 5. a narrow blind sac extending from the beginning of the colon that stores lymph cells 7. the organ that manufactures bile and is the first to receive nutrients from the intestines 9. the organ that stores and concentrates bile 10. the top portion of the intestine HUN2201‐ Nutrition Anatomy (Chapter 3)‐ Study Outline Down
1. cartilage in the throat that guards the entrance to the trachea and prevents fluid or food from entering it when a person swallows 2. the lower portion of the intestine that completes the digestive process and consists of four segments 4. a muscular, elastic, saclike portion of the digestive tract that grinds and churns swallowed food 6. a gland that secretes digestive enzymes and juices into the duodenum 8. the windpipe 7 Worksheet Digestion, Absorption, & Transport—DAT For each of the nutrients listed below, indicate the mechanism of action for each of the processes identified above. Nutrient Digestion/Enzyme Absorption
Hormonal Activation Regulation Carbohydrates Mouth → salivary Primary site = small Directly into the Insulin, glucagon amylase intestine, via active bloodstream Stomach → no active transport process Small intestine → pancreatic amylase Large intestine → fiber action Lipids Proteins Vitamins Minerals Water 1. 2. What dietary factors not listed above influence the processes of DAT? What structural factors not listed above influence the processes of DAT? HUN2201‐ Nutrition Anatomy (Chapter 3)‐ Study Outline 8 Worksheet: Food Habits, Digestion, and Absorption Digestion transforms the foods we eat into nutrients and absorption moves nutrients from the GI tract into the blood. Optimal digestion and absorption depends on the good health of the digestive tract, which is affected by such lifestyle factors as sleep, physical activity, state of mind, and the meals you eat. 1. Identify which of these foods and food habits promote or impede healthy digestion and absorption. Foods and Food Habits Promote
Impede a. Take small bites of food. b. Chew thoroughly before swallowing. c. Exercise immediately after eating to prevent weight gain. d. Eat a low‐fiber diet. e. Drink plenty of fluids. f. Eat a few large meals instead of several smaller ones. g. Eat quickly and then lie down to rest. h. Create a meal using citrus fruits and meat. i. Tackle family problems at the dinner table. 2. Do you experience GI distress regularly? 3. What changes can you make in your eating habits to promote GI health? HUN2201‐ Nutrition Anatomy (Chapter 3)‐ Study Outline 9 Handout: Transport of Nutrients into the Blood Nutrient Transport into Blood Water‐soluble nutrients Carbohydrates Monosaccharides Directly into blood Lipids Proteins Amino Acids Directly into blood Vitamins Vitamins B and C Directly into blood Minerals Directly into blood Fat‐soluble nutrients Lipids Long‐chain fatty acids Made into triglycerides Monoglycerides Made into triglycerides Triglycerides To lymph, then blood Cholesterol To lymph, then blood Phospholipids To lymph, then blood Vitamins Vitamins A, D, E and K To lymph, then blood HUN2201‐ Nutrition Anatomy (Chapter 3)‐ Study Outline ...
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- Fall '08
- Large intestine, digestive tract, GI Tract, nutrition anatomy, b. Chew