Focus on digestive disorders
According to the National Digestive Diseases Information Clearinghouse (NDDIC) of the United States Department of Health and Human Services (http:/
More than likely, you or a family member has experienced one or more of the digestive disorders listed in the table below. Using information provided on page 68, in Infographic 3.11, and through the NDDIC website at http:/
| DIGESTIVE DISORDERS— |
POSSIBLE CAUSES | PREVENTION AND/OR TREATMENT— |
|---|---|---|
| Constipation— |
Lack of dietary fiber and lack of physical activity | Consume a diet with adequate fiber (20– |
| Diarrhea | ||
| Diverticular disease | ||
| Gallstones | ||
| Gastritis | ||
| Gastroesophageal reflux disease (GERD) | ||
| Heartburn | ||
| Hemorrhoids | ||
| Inflammatory bowel disease (IBD) | ||
| Irritable bowel syndrome (IBS) | ||
| Ulcer | ||
| Vomiting |
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The process of digestion makes nutrients available for absorption and use in the body.
The primary organs of the gastrointestinal (GI) tract include the mouth, esophagus, stomach, small intestine, and large intestine. The lumen, or inner space of the GI tract, is lined by mucosal cells that allow our body to absorb nutrients, so that they can be transported by the blood or lymph to where they are needed.
The digestive system includes accessory organs that secrete fluids containing a variety of agents that aid in digestion and include the salivary glands, liver, gallbladder, and pancreas.
Mechanical digestion, which begins in the mouth, involves the physical fragmentation of foods into small particles. Food is mixed with digestive fluids, propelled along the GI tract through two patterns of contractions of the smooth muscles called peristalsis and segmentation.
Chemical digestion involves specific enzymes and other secretions that break down the chemical compounds in food.
Enzymes are protein molecules that catalyze, or speed up, the rate at which a chemical reaction produces new compounds with altered chemical structures.
Hormones are chemical messengers that participate in the control and regulation of body processes.
The stomach secretes gastric juices that contain hydrochloric acid and nutrient-
The small intestine is the primary site where the chemical digestion of food and the absorption of nutrients are accomplished. The small intestine has structural features—
Nutrients enter mucosal cells along the GI tract through simple diffusion and facilitated diffusion, as well as through active transport.
From the brush border, nutrients either enter the blood immediately, or first enter the lymphatic system and then are distributed to tissues and organs via the blood.
Probiotics are live, beneficial bacteria found in fermented foods that can restore or maintain a healthy balance of “friendly” bacteria in the GI tract. Prebiotics are nondigestible carbohydrates broken down by bacteria in the large intestine that foster the growth of beneficial bacteria.
Digestive disorders affect millions of people each year and diminish quality of life and overall health. Diet may play an important role in the prevention and treatment of these conditions.
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Review Questions
1. The primary organ for digestion and absorption in the body is the:
stomach.
liver.
colon.
small intestine.
1. d
2. All of the following are functions of the mouth in digestion, EXCEPT:
the mechanical breakup of food.
the moistening and mixing of food.
the secretion of protease to begin protein digestion.
the secretion of amylase to begin starch digestion.
2. c
3. Chemical digestion of food includes:
chewing of food in the mouth.
gastric acids in the stomach.
peristalsis and segmentation.
the incorporation of fatty acids into chylomicrons.
3. b
4. All of the following are true regarding enzymes that participate in the process of digestion, EXCEPT:
they are secreted by the salivary glands, stomach, pancreas, and small intestine.
they speed up chemical reactions that break down food.
they are changed by the chemical reactions they facilitate.
they can participate in chemical reactions many times.
4. c
5. Chemical substances that act as messengers between organs to cause the release of secretions needed for digestion and other body processes are termed:
chylomicrons.
lipoproteins.
enzymes.
hormones.
5. d
6. During digestion, the stomach gradually ejects small amounts of semi-
chyme; small intestine
bolus; esophagus
chylomicrons; colon
bile; jejunum
6. a
7. Structures that increase the surface area of the small intestine are called:
chyme.
villi.
mucosa cells.
sphincters.
7. b
8. Absorption is the process by which:
excess calories are incorporated into adipose tissue.
nutrients are converted into ATP.
food moves from the esophagus into the stomach.
nutrients pass through the intestinal mucosa into the blood or lymph.
8. d
9. Both facilitated diffusion and active transport of nutrients into cells require:
specific transport proteins.
energy.
transport fatty acids.
enzymes.
9. a
10. From inside the cells of the brush border most fats are absorbed into:
blood vessels.
lymph vessels.
triglycerides.
arterial cholesterol deposits.
10. b
11. Food sources of prebiotics that foster growth of good bacteria in the large intestine include all of the following, EXCEPT:
oats.
fermented products.
barley.
wheat.
11. b
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12. A digestive disorder that affects the muscle contractions of the colon and is characterized by a group of symptoms that include abdominal pain, bloating, diarrhea, and other possible GI symptoms is termed:
celiac disease.
gastrointestinal reflux disease.
irritable bowel syndrome.
diverticular disease.
12. c
Take It Further
Describe the differences in the muscular movements of peristalsis and segmentation, and the way they assist in digestion. After digestion, the next step is absorption by the mucosal cells of the small intestine. Describe the features of the small intestine that make it possible to maximize the absorption of nutrients.
Take charge of your digestive health
Now that you have learned about the structures and functions associated with the digestive process, you can begin to think critically about how the foods you eat may or may not support a healthy digestive environment.
To begin, keep a journal of everything you eat for three full days. It is important to include all food and drink items you consume during this three-
After completing your three-
To do this, follow the steps below:
1. Log onto the United States Department of Agriculture (USDA) website at www.supertracker.usda.gov. If you have not done so already, you will need to create a profile to get a personalized diet plan. This profile will allow you to save your information and diet intake for future reference. Do not use the general plan.
2. Click the Track Food and Activity option.
3. After you have entered your food for each day, you can then use the “My Reports” feature to analyze your intake. The “Food Groups and Calories” report shows your average intake for each food group. It also shows average calorie intake. The “Nutrients Report” shows an average intake of specific nutrients (such as sodium, calcium, and vitamin D), as well as the foods you consumed that provide the highest or lowest amount of each nutrient.
4. Once you have had a chance to generate and review these two reports, reflect on the results of your analysis by answering the following questions:
In which food groups are you meeting your daily targets? Based on what you have learned in this chapter, what, if any, are the digestive benefits of consuming your target amount in these groups?
In which food groups are you falling short of your daily targets? What are the possible digestive implications of not meeting your daily targets in these groups?
Does your analysis show that you are eating foods that offer additional digestive benefits, such as probiotics and prebiotics? Which foods in your intake fall in this category?
Based on your analysis, write two goals that relate to making dietary choices that promote proper digestion.