Download 5 Digestive System and Nutrition

PART II
MAINTENANCE OF THE HUMAN BODY
5
Digestive System and Nutrition
6
Composition and Function of the Blood
7
Cardiovascular System
8
Lymphatic System and Immunity
9
Respiratory System
10 Urinary System and Excretion
Chapter 5 Digestive System and Nutrition
BEHAVIORAL OBJECTIVES
1. Trace the path of food through the digestive system from the mouth to the anus. [5.1, p.82, Fig. 5.1, Table 5.1]
2. Describe the features and structures of the mouth that prepare food for swallowing. [5.1, p.82-83, Fig. 5.2]
3. Explain how the structure of the pharynx ensures the passage of food into the esophagus and not the trachea.
[5.1, p.84, Fig. 5.3]
4. Discuss the features of the esophagus and how muscular contractions regulate passage of food into and out of
this structure. [5.1, p.85, Fig. 5.4]
5. Describe the structure and function of the four layers of tissues in the digestive tract. [5.1, p.85, Fig. 5.4]
6. Explain how the stomach is structurally adapted to high acidity. [5.1, p.86, Fig. 5.5]
7. Relate the function of the small intestine to its unique structure. [5.1, p.87, Fig. 5.6]
8. Explain how microvilli enhance absorption. [5.1, p.87, Fig. 5.6]
9. Discuss how digestive secretions are under hormonal control, and list the hormones involved. [5.1, p.88, Fig.
5.7]
10. Name and describe the sections of the large intestine and the functions of the colon. [5.1, pp.88-89, Fig. 5.8 &
5.9]
11. Explain how pancreatic secretions aid digestion. [5.2, p.90]
12. List several functions of the liver, and describe the gallbladder and the role of bile in digestion. [5.2, pp.90-91,
Fig. 5.10]
13. Describe the hepatic portal system. [5.2, p. 91, Fig. 5.11]
14. Name the major disorders of the liver and discuss their causes. [5.2, p.91]
15. List ways the liver helps to maintain homeostasis. [5.2, p.91]
16. Name the major digestive enzymes, the type of nutrient they digest, the products of digestion, and the organ in
which they are produced. [5.3, p.92; 93, Table 5.2]
17. Describe how the different classes of nutrients enter the body’s general circulation. [5.3, p.92]
18. Describe the role of the digestive system in homeostasis. [5.4, p.95]
19. Discuss how the digestive system interacts with other body systems to maintain homeostasis. [5.4, pp.94-95,
Human Systems Work Together]
20. Discuss proper nutrition and how carbohydrates, protein, and fat should be proportioned in the diet. [5.5, pp.9598, Fig. 5.13 & 5.14, Table 5.4]
21. Discuss safe ways to lose weight. [Health Focus, p.99]
22. Describe ways to control dietary intake of sugar, lipids, and sodium (salt). [5.5, pp.96, 98, 103, Tables 5.3, 5.5,
5.8]
23. Discuss the vitamin and mineral requirements in the diet. [5.5, pp.100-103, Tables 5.6, 5.7, 5.8 and Fig. 5.17]
24. Describe the three principal eating disorders and their treatments. [5.5, pp.104-105, Figs. 5.18, 5.19, & 5.20]
25. Understand and use the bold-faced and italicized terms included in this chapter. [Understanding Key Terms,
p.107]
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EXTENDED LECTURE OUTLINE
5.1 The Digestive System
The Mouth
A roof, formed by the hard and soft palates, separates the mouth from the nasal cavities Three pairs of salivary
glands secrete saliva (containing salivary amylase for digestion of starch to maltose) into the mouth, where the teeth
chew the food and the tongue forms a bolus for swallowing.
The Teeth
Each tooth has a crown and a root. The crown has a layer of enamel, dentin, and an inner pulp. The root has
dentin and pulp. Blood vessels and nerves are in the pulp.
The Pharynx
The air passage and food passage cross in the pharynx. When one swallows, the air passage is usually blocked off
and food must enter the esophagus. Swallowing is a reflex performed automatically.
The Esophagus
The esophagus is a muscular tube that conducts food through the thoracic cavity and diaphragm into the stomach.
Peristalsis begins in the esophagus. Sphincters guard the entrance and exit of the esophagus.
The Wall of the Digestive Tract
The wall of the disgestive tract has these layers: mucosa (mucous membrane) submosca (loose connective tissue),
muscularis (smooth muscle) and serosa(serous membrane).
The Stomach
The stomach expands and stores food. While food is in the stomach, it churns, mixing food with the acidic gastric
juices (contain HCl and pepsin for the digestion of protein to peptides) to produce chyme.
The Small Intestine
The duodenum receives bile from the gallbladder and pancreatic juices (contain pancreatic lipase, trypsin for
digestion of protein to peptides, and lipase for digestion of fat to glycerol and fatty acids). Pancreatic juice is basic
because of the presence of NaHCO3). The walls of the small intestine have fingerlike projections called villi where
nutrient molecules are absorbed into the cardiovascular and lymphatic systems. The lymphatic capillary in a villus is
called a lacteal. Enzymes that finish the process of digestion are produced by the intestinal wall.
Regulation of Digestive Secretions
Gastrin produced by the lower part of the stomach stimulates the stomach to produce digestive juice. Secretin and
CCK (cholecystokinin) produced by the duodenal wall, stimulate the pancreas to secrete digestive juice and the
gallbladder to release bile.
The Large Intestine
The large intestine consists of the cecum, colon (ascending, transverse, descending, and sigmoid), and the rectum,
which ends at the anus. The large intestine does not produce digestive enzymes; it does absorb water, salts, and
some vitamins.
Polyps
Polyps are small growths arising from the epithelial lining.
Diarrhea and Constipation
The major causes of diarrhea are infection of the lower tract and nervous stimulation. Water and fiber in the
diet can prevent constipation.
Mader VRL CD-ROM
Image 0095a.jpg (Fig. 5.1)
Image 0095bl.jpg (Fig. 5.1)
Image 0095cl.jpg (Fig. 5.1)
Image 0096l.jpg (Fig. 5.2a)
Image 0097l.jpg (Fig. 5.2b)
Image 0098l.jpg (Fig. 5.3)
Image 0099l.jpg (Fig. 5.4)
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Mader VRL CD-ROM, con’t.
Image 0100l.jpg (Fig. 5.5)
Image 0101al.jpg (Fig. 5.6)
Image 0101bl.jpg (Fig. 5.6)
Image 0102l.jpg (Fig. 5.7)
Image 0103l.jpg (Fig. 5.8)
Image 0104l.jpg (Fig. 5.9)
Dynamic Human CD-ROM
Digestive/Anatomy/3D Viewer
Digestive/Anatomy/Gross Anatomy
Digestive/Histology/Tooth
Digestive/Histology/Tongue
Digestive/Histology/Submandibular Gland
Digestive/Histology/Esophagus
Digestive/Histology/Fundic Stomach
Digestive/Histology/Duodenum
Life Science Animations VRL 2.0
Digestive/Histology/Duodenal Villus (i)
Animal Biology/Digestive System/Human Digestive Tract
Animal Biology/Digestive System/Digestion
Animal Biology/Digestive System/Anatomy of Intestinal
Lining
Mader ESP Modules Online
Transparencies
Animal Biology/Digestive System/Digestion (Mouth to
Stomach)
Animal Biology/Digestive System/Digestion (Stomach)
Animal Biology/Digestive System/Stomach Digestion
Animal Biology/Digestive System/Digestion (Stomach to Small
Intestine)
Animal Biology/Digestive System/Small Intestine Digestion
Animals/Digestion/Introduction
Animals/Digestion/Human Digestion
Animals/Digestion/Mouth and Esophagus
Animals/Digestion/Stomach
Animals/Digestion/Small Intestine
Animals/Digestion/Large Intestine
66 (Fig. 5.1)
67 (Fig. 5.2)
68 (Fig. 5.3)
69 (Fig. 5.4a)
70 (Fig. 5.5a)
71 (Fig. 5.6)
72 (Fig. 5.7)
73 (Fig. 5.8)
74 (Fig. 5.9)
5.2 Three Accessory Organs
The three accessory organs of digestion—the pancreas, liver, and gallbladder—send secretions to the duodenum via
ducts.
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The Pancreas
The pancreas produces pancreatic juice, which contains digestive enzymes to break down carbohydrate (i.e.,
pancreatic amylase), protein (i.e. trypsin), and fat (i.e., lipase).
The Liver
The liver produces bile, which is stored in the gallbladder. The liver receives blood from the small intestine by way
of the hepatic portal vein. It has numerous important functions, and any malfunction of the liver is a matter of
considerable concern.
Liver Disorders
Jaundice, hepatitis, and cirrhosis are three serious disorders that affect the functioning of the liver.
The Gallbladder
The gallbladder stores bile until it is sent to the duodenum. Bile emulsifies fat exposing small droplets to the action
of lipase. Gallstones are crystals of cholesterol.
Mader VRL CD-ROM
Image 0105l.jpg (Fig. 5.10)
Image 0106l.jpg (Fig. TA5.1)
Image 0107l.jpg (Fig. 5.11)
Dynamic Human CD-ROM
Digestive/Histology/Liver
Digestive/Histology/Gallbladder
Digestive/Clinical Concepts/Gallstones
Life Science Animations VRL 2.0
Animal Biology/Digestive System/Formation of Gallstones
Mader ESP Modules Online
Animals/Digestion/Accessory Organs
Transparencies
75 (Fig. 5.10)
76 (Fig. 5.11)
5.3 Digestive Enzymes
Digestive enzymes are present in digestive juices and break down food into the nutrient molecules glucose, amino
acids, fatty acids, and glycerol (see Table 5.2). Glucose and amino acids are absorbed into the blood capillaries of
the villi. Fatty acids and glycerol rejoin to produce fat, which enters the lacteals. Digestive enzymes, like other
enzymes, speed specific reactions and function best at a warm body temperature and optimum pH.
Conditions for Digestion
For digestion to occur the correct enzyme, optimum pH, optimum temperature and the correct substrate must be
present.
Mader VRL CD-ROM
Image 0108l.jpg (Fig. 5.12)
Dynamic Human CD-ROM
Digestive/Explorations/Digestion Overview
Digestive/Explorations/Pepsin Formation
Digestive/Explorations/Intestinal Villus
Mader ESP Modules Online
Animals/Digestion/Enzymes and Hormones
Transparencies
77 (Table 5.2)
78 (Fig. 5.12)
5.4 Homeostasis
In general the digestive system contributes to homeostasis by supplying the body with nutrient molecules that are
used as a source of energy and building blocks or synthetic reactions. A Human Systems Work Together diagram
shows how the digestive system works with other systems in the body to maintain homeostasis.
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Mader VRL CD-ROM
Image 0109al.jpg (Fig. TA5.2)
Image 0109bl.jpg (Fig. TA5.2)
Dynamic Human CD-ROM
Digestive/Clinical Concepts/Barium Radiograph
Digestive/Clinical Concepts/Dental Cavity
Digestive/Clinical Concepts/Endoscopy
Life Science Animations VRL 2.0
Transparencies
Digestive/Clinical Concepts/Ulcer
Animal Biology/Digestive System/Dental Caries
Animal Biology/Digestive System/Plaque Formation
Animal Biology/Digestive System/Ulcers
Animal Biology/Digestive System/Endoscopy
79 (Fig. TA5.1)
5.5 Nutrition
The U.S. Department of Agriculture recommends a diet high in carbohydrates, at least five servings of fruits and
vegetables and limited but adequate protein. Fats and oils should be used sparingly.
Carbohydrates
To meet energy needs, dietitians recommend consuming food rich in complex carbohydrates like breads and pasta.
Simple carbohydrates like table sugar (sucrose) are not recommended. Fiber helps regularity and may help prevent
cancer.
Proteins
Dietary meat does assure that all the essential amino acids are acquired but this is also possible by consuming a
combination of legumes, grains, vegetables, seeds and nuts (see Table 5.4).
Lipids
Lipids, like fats and oils, should be used sparingly because they contribute to the development of plaque on blood
vessels walls.
Fake Fat
Olestra is made to look, taste, and act like fat but the digestive system cannot digest it. The fat soluble
vitamins are taken up by and pass through the digestive system with olestra. Carotenoids are also under
absorbed.
Vitamins
Vitamins are organic compounds that the body is unable to produce but needs for metabolic purposes. Many
vitamins are portions of coenzymes. Table 5.6 lists the fat-soluble and Table 5.7 lists the water-soluble vitamins.
Antioxidants
The vitamins A, E, and C are antioxidants that protect cell contents from damage due to free radicals.
Vitamin D
A precursor molecule in skin is converted to vitamin D after exposure to UV light rays. Vitamin D is
modified first in the kidneys and then the liver until calcitriol results. Calcitriol is needed for calcium
absorption.
Minerals
The body contains more than 5 grams of each macromineral and less than 5 grams of each micromineral. Table 5.8
lists both types of minerals.
Calcium
Calcium is needed to have strong bones and older women in particular are at risk for osteoporosis, a
degenerative bone disease due to insufficient intake of calcium and/or uptake of calcium by their bones.
Sodium
Most Americans have too much sodium in their diet. Salt intake leads to hypertension in some persons.
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Eating Disorders
Obesity
Obesity is defined as a body weight of more than 20% above the ideal weight for that person. Obesity can
have genetic, hormonal, and behavioral causes. For many a sensible diet and exercise program can control
obesity.
Bulimia Nervosa
Bulimia nervosa is characterized by a restrictive diet, excessive exercising and purging.
Anorexia Nervosa
Anorexia nervosa is characterized in the same way as bulimia except that the individual has a distorted
body image and feels fat even when emaciated.
Mader VRL CD-ROM
Image 0110l.jpg (Fig. 5.13)
Image 0111l.jpg (Fig. 5.14)
Image 0112l.jpg (Fig. 5.15)
Image 0113l.jpg (Fig. 5A)
Image 0114l.jpg (Fig. 5.16)
Image 0115l.jpg (Fig. 5.17)
Image 0116l.jpg (Fig. 5.18)
Image 0117l.jpg (Fig. 5.19)
Image 0118l.jpg (Fig. 5.20)
Image 0119l.jpg (Fig. TA5.3)
Life Science Animations VRL 2.0
Animal Biology/Digestive System/Ideal American Diet
Mader ESP Modules Online
Animals/Digestion/Nutrition
Why You Should Buy Organic Coffee: It Helps Migratory Birds
and Other Forest species
Could Your Inner Clocks Make You the Junk Food Junkie?
Got Milk?? Part 2
Food of the Gods
Ireland: The White Potato
Ethiopia: Coffee
Southeastern Asia: Tea
Indonesia: Golden Rice Is Life
Bulimia
80 (Fig. 5.13)
Case Studies Online
Transparencies
81 (Fig. 5.15)
82 (Fig. 5.17)
83 (Fig. TA5.2)
SEVENTH EDITION CHANGES
New/Revised Text:
This was chapter 4 in the previous edition.
5.5 Nutrition. In the discussion of calcium, the usefulness of vitamin D and other vitamins in preventing
osteoporosis is presented. The Health Focus “Weight Loss the Healthy Way” has been revised to improve clarity.
New/Revised Figures:
5.3 Swallowing; 5.7 Hormonal control of digestive gland secretions
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STUDENT ACTIVITIES
Diet log
1. Keep a comprehensive log of everything you eat for one week—including all snacks. Now compare this to the
food pyramid. How well balanced is your diet? Is it difficult to eat well when you “eat out” often? What
would be the easiest and least expensive way to improve your diet? What benefits might you gain by doing
this?
The hug of life
2. Have a trained rescuer explain and demonstrate the Heimlich maneuver. Discuss the dangers of performing
this too energetically. Should you attempt this maneuver on anyone choking? How would you know when to
perform this? Is there a different procedure used for an unconscious person? An infant?
Popular Diet Plans
3. Ask a registered dietician to come to class to discuss the merits and drawbacks of several popular diet schemes
(e.g., NutriSystems, Jenny Craig, Weight Watchers, TOPS, SlimFast). Allow students ample time to ask
questions. Be certain to have the dietician cover the following topics:
a. Will the person gain back lost weight after this diet plan?
b. Is it healthy for the body over the long term?
c. What weight-control plan should people follow?
d. What are the drawbacks to yo-yo dieting?
e. Why is a diet likely to fail unless exercise is incorporated?
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