Chapter 33: The Digestive System
LEARNING OUTCOMES
After completing Chapter 33, students should be able to:
33.1 Describe the organs of the alimentary canal and their functions.
33.2 Explain the functions of the digestive system’s accessory organs.
33.3 Identify the nutrients absorbed by the digestive system and where they are absorbed.
33.4 Describe the causes, signs and symptoms, and treatments of various common diseases and disorders of the digestive system.
Lecture Outline
Learning Outcome 33.1: Describe the organs of the alimentary canal and their functions.
•Lecture Topics
•Teach your students that digestion is the mechanical and chemical breakdown of foods into forms that your body cells can absorb. (Refer to PowerPoint Slide 4.)
•Begin the discussion of the digestive tract with the alimentary canal, distinguishing it from the accessory digestive organs. (Refer to PowerPoint Slides 5 – 7.)
•Ask your students to name the organs that make up the alimentary canal: mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, and anal canal. (Refer to PowerPoint Slides 8 – 16.)
•Explain that the alimentary canal consists of four layers and discuss the function of each layer:
•Mucosa: innermost layer that secretes enzymes and mucus, allowing for the absorption of nutrients.
•Submucosa: layer lined with blood vessels, connective tissue, nerves, and gland, which carries away the absorbed nutrients
•Muscular layer: consists of smooth [visceral] muscle that contracts to move material through the system.
•Serosa: outermost layer also known as the visceral peritoneum, which secretes serous fluid to keep organs from sticking to the alimentary canal. (Refer to Figure 33-2.)
•Review the functions of the following salivary glands:
•Parotid glands
•Submandibular glands
•Sublingual glands (Refer to Figure 33-6 and PowerPoint Slide 11.)
•Teach your students that the esophagus is a muscular tube that connects the pharynx to the stomach and explain the role of sphincters in digestion. (Refer to Figures 33-7 and 33-8 and PowerPoint Slide 17.)
•Review the anatomy of the stomach. Remind your students that the beginning portion of the stomach that is attached to the esophagus is called the cardiac region. The portion of the stomach that balloons over the cardiac region is the fundus. The main part of the stomach is called the body, and the narrow portion connected to the small intestine is the pylorus. The pyloric sphincter controls the movement of substances from the pylorus of the stomach into the small intestine. (Refer to Figures 33-8 and 33-9 and PowerPoint Slides 18 - 21.)
•Teach your students that eventually, the sigmoid colon straightens out to become the rectum. Note that the last few centimeters of the rectum are known as the anal canal, and the opening of the anal canal to the outside of the body is called the anus (Refer to Figure 33-10 and PowerPoint Slides 26 – 28.)
•Discussion Points
•Ask students to list the organs of the digestive system and write the responses on the board: mouth; pharynx; esophagus; stomach; small intestine; large intestine; rectum; anal canal; the accessory organs of the liver, gallbladder, and pancreas. Use these answers to prompt a discussion on the function of each organ.
•Explain to students that without a properly functioning digestive system, cells will not receive the nutrients needed to survive. (Refer to Figure 33-1.)
•Ask a volunteer to describe peristalsis: the movement or propulsion of substances through the alimentary canal. (Refer to Figure 33-2.)
•Remind your students that humans have 32 teeth—16 on the upper jaw and 16 on the lower jaw—which work to decrease the size of food particles. Discuss the functions of the following types of teeth: cuspids, bicuspids, and molars. (Refer to Figures 33-4 and 33-5 and PowerPoint Slide 12.)
•Discuss the role of the pharynx: to push food into the esophagus. Point out the divisions of the pharynx: nasopharynx, oropharynx, and laryngopharynx. (Refer to Figure 33-7.)
•Ask your students to describe the enzymes secreted by the small intestine: peptides, sucrose, maltase, lactase, and intestinal lactase. Remind them that the parasympathetic nervous system triggers the intestine to secrete these enzymes. (Refer to PowerPoint Slides 22 – 25.)
•Learning Activities
•Place the following words on the blackboard: buccal cavity, amylase, palate, lingual frenulum, uvula, pharynx, oropharynx, nasopharynx, and palatine tonsils. Ask your students to write a brief report on how mechanical and chemical digestion begin in the mouth using these words. Pick a few volunteers to read their reports to the class during a class discussion. (Refer to Figure 33-3.)
•Arrange your students into small groups and provide poster board and markers to each group. Ask you students to work together to create a poster that depicts the process that occurs when food is eaten, processed, and finally expelled from the body as feces. For fun, the students could vote on the best poster and a small award could be given to the group that created the poster.
Learning Outcome 33.2: Explain the functions of the digestive system’s accessory organs.
•Lecture Topics
•Emphasize the fact that although they do not form part of the alimentary canal, the digestive system’s accessory organs play important roles in digestion. That is, they deliver enzymes and other substances to the alimentary canal to assist with the digestive process.
•Discussion Points
•Ask your students to name the accessory organs of the digestive system. Place these labels on the board and have your students to describe the function of each organ: liver, gallbladder, and pancreas. (Refer to Figures 33-11 and 33-12 and PowerPoint Slides 32 – 38.)
•Learning Activities
•Invite a radiologist or gastroenterologist to speak to the class about diagnosing liver and gallbladder diseases seen on MRIs. Ask the speaker to bring some films in to show the class the abnormalities and to speak about how studies of these organs are prepared for the patient.
Learning Outcome 33.3: Identify the nutrients absorbed by the digestive system and where they are absorbed.
•Lecture Topics
•Tell your students that Harvard Medical International states a connection has been made between higher-fiber diets and a decrease in colon diseases, including cancer. Have your students explain why this connection might be made. (Fiber increases water absorption and bulk, causing more rapid emptying of the colon and decreasing the production of benign growths like adenomas or polyps, which increase the risk of cancer. Fiber may also neutralize toxins produced by GI (gastrointestinal) tract bacteria.)
•Teach your students that foods rich in protein include meats, eggs, milk, cheese, fish, chicken, turkey, nuts, seeds, and beans. Point out that the body uses proteins for growth and tissue repair.
•Discussion Points
•Ask students to define nutrients (necessary food substances) and to provide some examples of nutrients: carbohydrates, proteins, lipids, vitamins, minerals, and water. (Refer to PowerPoint Slide 41.)
•Discuss the three types of carbohydrates that humans ingest: starches (polysaccharides), simple sugars (monosaccharides and disaccharides), and cellulose. Brainstorm with the class to make a list of foods that are good sources of carbohydrates (e.g., bread, pasta, fruit). (Refer to PowerPoint Slide 42.)
•Ask a volunteer to define lipids. (Fats). Tell students that lipids are used by the body to make energy when sugar is low, and that a certain amount of fat is also needed to absorb fat-soluble vitamins (A, D, E, and K). Be sure to draw their attention to Table 33-1: Common Vitamins and Their Importance in the Body, which summarizes some common vitamins and their functions. (Refer to PowerPoint Slide 43.)
•Have your students explain why the body needs protein (growth and repair of tissues). Ask them to name foods that are high in protein. (e.g., meat, eggs, milk, fish, poultry, nuts, cheese, and legumes) (Refer to PowerPoint Slide 44.)
•Ask your students: What minerals are important to our bodies? (Calcium, phosphorus, sulfur, sodium, chlorine, and magnesium.) Point out that the minerals iron, manganese, copper, iodine, and zinc are also needed, but only in trace amounts.
•Learning Activities
•Have your students research how aging affects the digestive system and write a brief report to share with the class. (Refer to PowerPoint Slide 46.)
•Invite a registered dietician or nutritionist to the class. In preparation for the visit, ask class members to keep a food diary of everything they've eaten or drunk for at least two weeks. Ask some volunteers to share their diary as a way to initiate a discussion about good eating habits, especially in our "fast food" type of world. Be sure students prepare questions for the speaker.
Learning Outcome 33.4:Describe the causes, signs and symptoms, and treatments of various common diseases and disorders of the digestive system.
•Lecture Topics
•Review each disease discussed in the textbook. Stress to students that their understanding of the causes, signs and symptoms, and treatment of these disorders will assist them in their role as medical assistants. (Refer to PowerPoint Slides 47 – 52.)
•Discussion Points
•Be sure your students understand the diagnostic and therapeutic procedures used to diagnose and treat digestive diseases (sigmoidoscopy, colonoscopy, endoscopy, colectomy, colostomy, gastrectomy, gastrostomy, jejunostomy).
•Encourage questions and discussions on the common diseases and procedures discussed in the textbook. Many students will have had experience with, or know someone who has had experience with, at least one of these conditions. Encourage open discussion within the class.
•Learning Activities
•Have each student choose a digestive disease or disorder and complete additional research on the background of the disease, its causes or contributing factors, preventive measures (if any), treatment, and the prognosis for patients. This project may be an oral or written presentation.
Case Studies
•The following case studies can be presented to students so that you can assess their responses to situations they may encounter in the workplace setting.
•James Cho is a new patient who arrives at your clinic with a chief complaint of abdominal pain and vomiting, fatigue, and weight loss. He notes that although he has experienced overall weight loss, his stomach "looks huge." As his history is taken, he notes no alcohol use. In speaking with him, you notice a yellow tinge to the whites of his eyes. During examination, the physician notes organomegaly (organ enlargement) in the RUQ.
•What disease could James be suffering from? (Cirrhosis.) Which organ is enlarged? (Liver.) What is the clinical name for the yellow tint of his sclera? (Jaundice, or icterus.) If James does not drink alcohol, what are other possible causes for his condition? (Hepatitis B or C, autoimmune disease, or a possible reaction to medication.)
•Deanna Mathers is a 30-year-old woman with known eczema. She has been complaining recently of intermittent abdominal pain and fever, with severe bouts of diarrhea alternating with constipation. She does note that there has been blood in her stool, but states that she does not have hemorrhoids. Her physician comments that her eczema may be a clue as to her GI disturbance.
•What do you think her diagnosis may be? (Crohn's disease.) What are some of the treatment options? (Anti-inflammatory drugs; antibiotics; changes in diet; a partial or, in severe cases, total colectomy to remove the diseased intestine.)
Assessment
•Encourage students to use the various features in the Student Workbook for self-assessment. These features include vocabulary and content reviews, applications, case studies, and competency checklists (to assess mastery of procedures introduced in the chapter). You can assess students' grasp of the materials through a chapter test, using the vocabulary and content reviews. You can also refer to the activities and exercises on the Online Learning Center (OLC) and within the medical assisting student CD packaged with the student textbook.
Medical Assisting Media
Found on Connect Plus™
•Electronic Health Records (E.H.R.) SpringCharts® Exercises
•LearnSmart™
•BodyAnimat3d
•Administration and Clinical Administration Videos
•eBook (if you’ve adopted ConnectPlus)
•Online Learning Center™:
Resources
In addition to the publications listed on the OLC, you may find the following materials useful.
Books
Ballard, Carol. 2009. The Digestive System 2nd edition. Chicago, IL. Heinemann.
Hassett, Sue. 2009. Living with Celiac Disease. Philadelphia, PA. Xlibris Publishing.
Merrill, Gary. 2008. Our Marvelous Bodies: An Introduction to the Physiology of Human Health. Chapel Hill, NC. Longleaf Services.
Steinhardt, A. Hillary, Cepo, Julie. 2008. Crohn's and Colitis Diet Guide: Includes 150 Recipes. Ontario, Canada. Rose, Robert, Incorporated.
Articles
Brown, L.A. 2006. The fiber factor. Better Nutrition 68:30-31.
Drugs for the treatment of gastroesophageal reflux. 2006. Digestive Disorders:10-17.
Johns Hopkins Kimmel Cancer Center. 2006. Genome code cracked for breast and colon cancers. AScribe Health News Service, September 7.
What you might not know about digestive disorders. 2006. Digestive Disorders:10-11.
Audiovisuals
Cancer and Diet: Using Food to Eliminate Cancer. 2006. Bayview Films. DVD.
Computer Software
My Body, Myself. CD-ROM. Fogware Publishing. Windows 98/ME/XP Platforms.
Chapter 33 Textbook Answers
Case Study Critical Thinking
•The gallbladder stores bile for the body and releases it when prompted by the hormone cholecystokinin.
•She could have a lithotripsy procedure or medications to dissolve or break up the gallstones.
•If gallstones are not removed, inflammation of the cystic duct can spread to the common hepatic duct, and liver damage can result. Inflammation can also spread to the pancreatic duct, because it opens into the common bile duct, and serious pancreatic damage can occur.
•Most likely, Sylvia will not have to alter her diet because the liver will still produce bile. Because bile can no longer be stored, more of it will be emptied into the small intestine, possibly causing diarrhea.
Exam Preparation Questions
1.aMucosa
2.cLiver
3.buvula
4.dhernia
5.bCrohn’s disease
6.eBile
7.eTriglycerides
8.aTo help the large intestine empty more regularly.
9.bConstipation
10.cGastritis
Medical Terminology Practice
1.bi/cusp/id = bi means “two” + cusp means “projection” + id means “having the characteristic of”; bicuspid is a tooth that has two prominences or projections.
2.carboxy/peptid/ase = carboxy refers to carboxyl chemical groups + peptid refers to peptides (chemicals made of amino acids) + ase means “enzyme”; carboxypeptidase is an enzyme that breaks up peptides by removing carboxyl groups. This is one of the mechanisms by which proteins are digested.
3.diverticul/osis = diverticula are abnormal dilations or pouches in the intestinal wall + osis means “condition or disease”; diverticulosis is a condition in which diverticula are present in the intestine, but are not inflamed.
4.hepato/cyte = hepato refers to the liver + cyte means “cell”; hepatocytes are cells in the liver that process nutrients in blood and make bile.
5.idio/path/ic = idio means “self” or “from within” + path means “disease” + ic means “pertaining to”; idiopathic diseases are those with no known cause.
6.laryngo/pharynx = laryngeo refers to the larynx + pharynx is the throat; laryngopharynx is the part of the pharynx that lies behind the larynx.
7.nucle/ase = nucle refers to nucleic acids + ase means “enzyme”; a nuclease is an enzyme that digests nucleic acids.
8.poly/saccharide = poly means “many” + saccharide means “sugar”; polysaccharide is a type of carbohydrate that has many sugar molecules bonded together.
9.pylor/ic = pylor refers to the pylorus, or part of the stomach that connects to the small intestine + ic means “pertaining to”; pyloric means “pertaining to the pylorus.”
10.sub/lingual = sub means “under” + lingual refers to the tongue; sublingual means “under the tongue.”
Chapter 33 Student Workbook Answers
Vocabulary Review
Matching
1.i
2.t
3.c
4.y
5.a
6.l
7.v
8.d
9.o
10.f
11.s
12.x
13.b
14.p
15.j
16.q
17.g
18.w
19.e
20.h
21.k
22.m
23.u
24.n
25.r
True or False
(These are possible answers. Accept all reasonable responses.)
26.F: The parietal peritoneum is the lining of the abdominal cavity.
27.F: The mucosa is the innermost layer of the alimentary canal and is responsible for absorbing nutrients.
28.T
29.F: Amylase begins the digestion of carbohydrates.
30.T
31.F: The pharyngeal tonsils are also known as the adenoids.
32.F: The epiglottis covers the opening of the larynx.
33.F: The main part of the stomach is called the body.
34.T
35.F: If a patient’s stomach has been removed, a J tube may be inserted for feeding.
36.T
37.F: The liver is located in the right upper quadrant of the abdomen.
38.F: The descending colon becomes the sigmoid colon.
39.F: The liver makes bile, which is then stored in the gallbladder.
40.T
Content Review
Multiple Choice
1.c
2.c
3.b
4.d
5.e
6.a
7.c
8.b
9.e
10.d
Sentence Completion
11.parotid
12.diarrhea
13.esophageal hiatus
14.Nutrients
15.Intrinsic factor
16.K
17.acinar cells
18.Constipation
19.bicarbonate ions
20.small intestine
Short Answer
21.A.salivary glands
B.liver
C.gallbladder
D.pancreas
E.mouth
F.pharynx
G.esophagus
H.stomach
I.small intestine
J.large intestine
K.rectum
L.anus
22.A.esophagus
B.cardiac region
C.duodenum
D.pyloric sphincter
E.pyloric canal
F.pylorus
G.fundus
H.body
I.rugae
23.A.serosa
B.ascending colon
C.ileocecal sphincter
D.opening of vermiform appendix
E.cecum
F.vermiform appendix
G.rectum
H.muscular layer
I.mucosa
J.transverse colon
K.descending colon
L.sigmoid colon
M. anal canal
24.A.The production of visual receptors, mucus, the normal growth of bones and teeth, the repair of epithelial tissues
B.The metabolism of carbohydrates and fats, and cell growth
C.The production of collagen, amino acids, and hormones; the absorption of iron
D.the production of myelin and the metabolism of carbohydrates and nucleic acids
E.The production of amino acids, DNA, and red blood cells
F.The prevention of the breakdown of certain tissues