Download CHAPTER 17

CHAPTER 17
DIGESTIVE SYSTEM
OVERVIEW
This chapter is about the digestive system, which processes food so that nutrients can be absorbed and utilized by the cells. This
chapter begins with a description of the general functions of the digestive system and names the major organs of the digestive
system (Learning Outcomes 1,2). The structures and functions of the alimentary canal beginning with the mouth and teeth are
addressed (Learning Outcomes 3-6). The chapter continues with an examination of the secretions of the digestive system and the
mechanisms that regulate those secretions (Leaming Outcornes 7 9). Explanation of the control of movement of material through
the alimentary canal; descriptions of the mechanisn.rs of swallowing, vomiting, and defecating; and explanation of how the
products ofdigestion are absorbed conclude discussion ofthe stnrcture and function olthe digestive system (Leaming Outcornes
10-12). The chapter concludes with a description of aging-related changes in the digestive system (Leaming Outcome 13).
LEARNING OUTCOMES
After you have studied this chapter, you should be able to:
l7.I
Introduction (p. 652)
.
2.
Describe the general functions of the digestive system.
Name the major organs of the digestive system.
General Characteristics of the Alimentary Canal (p.652)
Describe the structure of the wail of the alimentary canal.
Explain how the contents of the alimentary canal are mixed and moved.
Mouth (p. 656)
Describe the functions of the structures associated with the mouth.
Describe how different types ofteeth are adapted for different functions, and list the parls
Salivary Glands Large Intestine (p. 660)
Locate each ofthe organs and glands; then describe the general function ofeach.
Identify the function ofeach enzyme secreted by the digestive organs and glands.
Describe how digestive secretions are regulated.
I
Explain control of movement of material through the alimentary canal.
I
Describe the mechanisms of swallowing, vomiting, and def'ecating.
Explain how the products ofdigestion are absorbed.
Lif'e-Span Changes (p. 690)
1
17.2
3.
4.
17.3
5.
6.
17.4-17.10
ofa tooth.
7.
8.
9.
0.
1.
12.
17.11
13.
Describe aging-related changes in the digestive system.
FOCUS QUESTION
How does the body make the nutrients in
a ham
sandwich available for utilization by the cells?
MASTERY TEST
Now take the mastery test. Do not guess. Some questions may have more than one correct answer. As soon as you complete the
test, correct it. Note your successes and failures so that you can read the chapter to meet your learning needs.
1.
The mechanical and chemical breakdown of food into forms that can be absorbed by cell membranes is
2.
The mouth, pharynx, esophagus, stomach, small intestine, and large intestine make up the
of the digestive system.
3.
4.
5.
The salivary glands, liver, gallbladder, and pancreas are considered
List the layers of the alimentary canal beginning with the innermost
a.
b.
6.
1ayer.
The vessels that nourish the structures of the alimentarv canal are found in the
c.
d.
mucous membrane
submucosa-
The two basic types of movernent of the alimentary canal are
movements.
l7l
muscular layer
serous layer.
movements and
7.
Does statement a explain statement b?
a.
b.
8.
Peristalsis is stimulated by stretching the alimentary tube.
Peristalsis acts to move food along the alimentary canal.
When the alimentary canal is being stimulated by the parasympathetic division,
a.
the impulses are arising in the
brain and the thoracic segment
ofthe spinal cord.
b.
newe impulses are conducted
c.
the activity
increased.
d.
sphincter tone in the anus is increased.
c.
d.
pleasure
ofthe organs ofthe digestive system
along the vagus nerve to the
esophagus, stomach, pancreas!
gallbladder, small intestine, and
parls of the large intestine.
9.
Which of the following is/are function(s) of the mouth?
a. speech
b. beginning digestion ofprotein
10.
I 1.
During swallowing, muscles draw the soft palate and uvula upward to
a.
b.
12.
13.
bicuspids.
canmes.
molars.
c.
d.
cementum.
dentin.
enamel.
plaque.
c.
d.
cleansing of mouth and teeth
dissolving chemicals necessary
for tasting food
helping in formation of food bolus
beginning digestion ofprotein
c.
submaxillary
sublingual
parotid
c.
d.
cardiac
tundic
body
pyloric
Forceful vomiting after feeding in a newbom is a sign of
The chiefcells ofthe gastric glands secrete
c.
d.
mucus.
hydrochloric acid.
digestive enzymes.
potassium chloride.
The digestive enzyme pepsin secreted by gastric glands begins the digestion of
a.
b.
24.
25.
c.
d.
When food enters the esophagus, it is transported to the stomach by a movement called
A chronic condition that replaces squamous epithelium with columnar epithelium is
region.
The area of the stomach that acts as a temporary storage area is the
a.
b.
23.
are
Stimulation of salivary glands by paraslmpathetic nerves will (increase/decrease) the production of saliva.
glands.
The salivary glands that secrete amylase are the
a.
b.
21.
22.
offood
incisors.
Which of the following tsnot a function of saliva?
a.
b.
18.
19.
20.
separate the oral and nasal cavities.
move the uurla from the path of the food bo1us.
The material that covers the crown of the teeth is
a.
b.
16.
17.
enlarge the area to
accommodate a bolus of food.
The teeth that bite offpieces
a.
b.
15.
c.
d.
move food into the esophagus.
The third set of molars is sometimes called the
a.
b.
14.
altering the size ofpieces offood
The tongue is anchored to the floor of the mouth by a fold of membrane called the
c.
carbohydrate.
fal
protein.
The intrinsic factor secreted by the stomach aids in the absorption of
lrom the small intestine.
The release ofthe hormone somatostatin (increases/decreases) the release ofhydrochloric acid by parietal cells.
172
is
26.
The release of gastrin is stimulated by
a.
b.
27.
28.
29.
c.
carbohydrate.
alcohol.
c.
d.
carbohydrate.
fat.
Pancreatic enzymes travel along the pancreatic duct and empty into the
c.
duodenum.
ileum.
jejunum.
Which of the following enzymes is present in secretions of the mouth, stomach, and pancreas?
c.
d.
amylase
lipase
tryps1n
lactase
Which of the following is secreted by the pancreas in an inactive form and is activated by a duodenal enzyme?
a.
b.
36.
37 .
fat.
Theenterogastricreflex(stimulates/inhibits)peristalsis.
The vomiting center is located in the
a.
b.
35.
somatostatin.
protein.
The substances absorbed from the stomach include
a. water.
a.
b.
34.
histamine.
offood in the small intestine eventually (inhibits/increases) gastric secretion.
The semifluid paste formed in the stomach by mixing food and gastric contents is
The foods that stay in the stomach the longest are high in
b.
31.
32.
33.
the parasympathetic nervous
system.
The presence
a.
b.
30.
c.
d.
the sympathetic nelvous system.
c.
d.
nuclease
trypsin
chymotrypsin
carboxypeptidase
The secretions ofthe pancreas are (acidic/alkaline).
The thick mucus that destroys lung and pancreatic tissue in victims of cystic fibrosis is the result
a.
abnormal mucus production that
causes increases in mucus.
c.
b.
a defect in mucous membrane
d.
of
defective chloride channels in the cell
membranes of many tissues.
adeficiencyofpancreatic enzyme production
shucture.
38.
39.
The liver is located in the
a.
b.
c.
40.
41.
carbohydrates.
fats.
proteins.
central vein.
liver capillaries.
hepatitis A.
hepatitis B.
hepatic sinusoids.
d.
e.
hepatitis D.
connective tissue ofthe lobes ofthe liver.
hepatitis E.
hepatitis C.
The function ofthe gallbladder is to
bile.
a. store
b. secrete
44.
c.
d.
The type(s) of hepatitis that is/are blood bome is/are
a.
b.
c.
43.
of
Extra iron is stored by the liver in the form of
Nutrients are brought to the liver cells via the
a.
b.
42.
quadrant of the abdomen.
The most vital liver functions are those that are related to metabolism
c.
d.
actlvate
concentrate
The hepatopancreatic sphincter is located between the
a.
pancreatic duct and the
bile
b.
duct'
common
c.
d.
hepatic duct and the cystic duct.
t73
common bile duct and the duodenum.
pancreatic duct and the duodenum.
45.
Which of the following is/are the function(s) of bile?
a.
b.
46.
47.
c.
d.
increase the solubility of amino acids
c.
d.
mucus secreted by the small intestine.
c.
d.
lipase.
a. red meat.
b. eggs.
c.
d.
leafy vegetables.
a. diffusion
b. osmosis
c.
d.
filtration
emulsification of fat globules
absorption offats
absorption of fat-soluble vitamins
List the poftions of the small intestine:
The velvety appearance ofthe lining ofthe small intestine is due to the presence of
a. cilia.
b. villi.
48.
a. sucrase.
b. maltase.
49.
50.
51
.
52.
53.
54.
milk and dairy products.
Which of the following transport mechanisms isiare not used by the small intestine?
Diarrhea results from an intestinal movement calied
Cholesterol is delivered to tissues by
bv-
active transport
; cholesterol is removed from tissues and delivered to the
.
The small intestine joins the large intestine at the
The only significant secretion
ofthe large intestine is
c.
d.
potassium.
mucus.
chyme.
water.
The only nutrients normally absorbed in the large intestine are
Which of the following are synthesized by the bacteria of the colon?
a.
b.
57.
intestinal amvlase.
Lactose intolerance leads to an inability to digest
a.
b.
55.
56.
capillaries.
The intestinal enz;We that breaks down fats is
c.
d.
gas
electrolytes
vitamin
and
K
ascorbic acid
The most noticeable signs ofaging on digestion appear in the
a.
b.
c.
d.
mouth.
accessory organs.
t74
small intestine.
large bowel.
liver
STUDY ACTIVITIES
Definition of Word Parts (p. 651)
Define the following word parts used in this chapter.
aliment-
caicec-
chymdecidufrenulgastrhepat-
hiat-
linguperipv1-
rectsorpt-
vill-
17.1 Introduction @. 652)
A.
Define digestion.
r75
Label the numbered structures on the diagram ofthe digestive system
B.
A
{n*+ri\
\i/'
2./s
ACCESSORY ORGANS
ALIMENTARY CANAL
1
Secrete saliva, which contains
enzymes that initiate breakdown
of carbohydrates
5
Mechanical breakdown
of food; begins chemical
digestion of carbohydrates
b
Connects mouth with
esophagus.
7
Peristalsis pushes
food to stomach
I
Secretes acrd and
enzymes. Mixes lood
with secretions to
begin enzymatic
digestion of proteins
Produces bile, which
emulsifies fat
3Stores bile and
introduces it into
small intestine
9
Mixes food with bile
and pancreatic juice.
Final enzymatrc breakdown
of food molecules;
main site of
nutrient absorption
Produces and secretes
pancreatic juice, containing
digestive enzymes and
bicarbonate ions,
into small intestine
10
Absorbs water and
electrolytes to form feces
11
Regulates elimination
of feces
12
176
17.2 General Characteristics of the Alimentary Canal (p. 652)
A.
Fill in the following chart.
Structure and Function of the Alimentary Canal
Composition
Function
Mucosa or mucous membrane
Submucosa
Muscular layer
Serosa or serous membrane
B.
C.
D.
The two types of movement of the alimentary tube are
Parasympathetic stimulation provokes a/an
provokes a/an
in the activity of the tube.
and
Bowel sounds heard through a stethoscope placed on the abdomen are due to
17.3 Mouth (p. 656)
A.
What are the functions of the mouth?
B.
Answer the following conceming the cheeks and 1ips.
1.
Describe the structure of the cheeks.
2.
Describe the structure of the lips.
3
C.
D.
.
Why are cheek cells used as a source of DNA for genetic testing?
Answer the following concerning the tongue.
1.
Describe the muscular structure of the tongue.
2.
What is the function of the tongue?
Answer these questions conceming the palate.
1
.
What are the parts of the palate?
2.
What is the function of the palate?
3.
Why is infection of the palatine tonsils significant?
r77
_.
in the activity of the tube; sympathetic stimulation
Where are the adenoids located?
E.
Answer the following conceming the teeth.
1.
Use yourselfor a partner to locate the central incisors; lateral incisors; cuspids; first bicuspids; second bicuspids;
and first, second, and third molars. Are the wisdom teeth present?
2.
Describe the development of teeth.
3.
In the following iilustration ofa tooth, label the parts identified by letters.
4.
Identifu the functions of the following kinds of teeth.
incisors
canines (cuspids)
premolars and molars
r78
17.4 Salivary Glands (p. 660)
A.
B.
Answer these questions concerning salivary glands and their secretions.
1.
What is the function of salivary glands?
2.
What stimulates them to secrete saliva?
Fill in the following chart.
Salivary Glands
Gland
Location of the
Gland
Secretion
Location of the Duct
Parotid
Submandibular
Sublingual
17.5 Pharynx and Esophagus (p. 661)
A.
Describe the nasophaqmx, oropharynx, and laryngophaq'nx. In the description, include the muscles in the wall
of the larynx.
B.
List the events of swallowing.
C.
Describe the structure and functions ofthe esophagus.
D.
The esophagus passes through the diaphragm via an opening called the
E.
What is a hiatal hemia?
F.
What is the significance of Barrett's esophagus?
17.6 Stomach (p. 665)
A.
Answer the following conceming the stomach and its parts
1.
What are the functions of the stomach?
t79
2.
Label the indicated regions of the stomach identified by letters
B.
Describe the mucous membrane of the stomach.
C.
Fill in the following chart.
Secretions of Gastric Glands
Cell Type
Secretions
Mucous cell
Chief ce1l
Parietal cell
D.
How are gastric secretions regulated?
E.
Describe the three phases ofgastric secretion.
F.
What is the "aikaline tide"?
180
Function and Action
G.
List the substances absorbed from the stomach.
H.
Answer the following concerning filling and emptying actions.
1.
What is chyme, and how is it produced?
2.
What factors affect the rate at which the stomach empties?
3.
Describe vomiting.
17.7 Pancreas (p. 671)
A.
Where is the pancreas located?
B.
Answer the following concerning pancreatic juice.
1.
Describe the action of the following pancreatic enzyrnes
amylase
lipase
trypsin
chyrnotrypsin
carboxlpeptidase
2.
Describe acute pancreatitis.
3.
What substance makes the pancreatic juice alkaline?
4.
Describe the neural mechanisms that regulate pancreatic secretion.
5.
How does cholecystokinin affect pancreaticjuice?
l8l
17.8 Liver (p.673)
A.
Answer the following conceming the liver.
L
Describe the location and structure ofthe liver. Include the circulation to the liver.
2.
What is the role of the liver in carbohydrate metabolism?
3.
What is the role of the liver in fat metabolism?
4.
What is the role of the liver in protein metabolism?
5.
How does hepatic coma develop?
6.
What is the role of the liver in iron homeostasis?
7.
What is the digestive function of the liver?
B.
Describe the types of hepatitis. Be sure to include the treatment and mode of transmission of each type.
C.
Answer the following questions conceming bile.
D.
L
Describe the composition of bile.
2.
3.
Bile pigments, bilirubin and biliverdin, are the breakdown products of
What causes jaundice?
Answer the following questions about the gallbladder.
Where is the gallbladder located and what is its flrnction?
1.
2.
Describe the ducts between the gallbladder and the duodenum. Please include a discussion ofthe sphincters.
3.
How are gallstones formed?
4.
How is the release ofbile regulated?
5.
What are the functions of bile?
t82
17.9 Small Intestine (p. 678)
A.
Name and locate the three portions of the small intestine.
B.
The peritoneal membrane that forms a membranous apron over abdominal contents is the
C.
Label the structures in the following illustration: simple columnar epithelium, lacteal, blood capillary network,
intestinal gland, goblet cells, arteriole, venule, lymph vessel, viltus.
7
8
o
D.
What is the function of the villi?
Describe the mechanisms that regulate intestinal secretions.
183
F.
Major Digestive Enzymes
Enzyme
Source
Digestive Action
Salivary enzymes
Amylase
Gastric enzymes
Pepsin
Gastric lipase
Pancreatic enzymes
Amylase
Pancreatic lipase
Trypsin
Chymotrypsin
Carboxypeptidase
Nucleases
Intestinal enzymes
Peptidase
Sucrase, maltase, lactase
Intestinal lipase
Enterokinase
r84
J
G.
H.
Answer the following concerning absorption in the small intestine.
1.
List the substances absorbed in the small intestine.
2.
Describe fat absorption. Begin with the role of chylomicrons.
3.
What ions are readily absorbed?
4.
What ions are poorly absorbed?
Answer the following conceming the movements of the small intestine'
1. a.
b.
The normal movements of the small intestine
are
and
The major mixing movement is
2.
How are these movements regulated?
3.
The result of peristaltic rush is
4.
What separates the small and large intestine? How does this structure work?
-,
185
movements-
17.10 Large Intestine (p. 686)
A.
Label the parts of the large intestine identified
by numbers'
5
b
Answer these questions about the large intestine.
1.
List and locate the parts ofthe large intestine.
2.
How does the structure of the large intestine differ from that of the small intestine?
Answer these questions conceming the functions of the large intestine'
I
. How is the rate of mucus
2. What
f.
secretion controlled?
is the function of mucus?
What substances are absorbed in the large intestine, and what transport mechanisms are used?
4. What is the function
of the bacteria in the colon?
186
D.
Answer the following conceming the movements of the large intestine.
i . Describe the movements of the large intestine.
2.
E.
List the events ofthe defecation reflex-
What is the composition of feces?
17.11 Life-Span Changes (p. 690)
A.
Describe life-span changes in the following parts of the digestive system.
mouth
esophagus
stomach
small intestine
large intestine
pancreas
liver
gallbladder
187
Clinical Focus Question
Your grandmother is 80 years old, and both she and your grandfather describe themselves as being in excellent health. Your
grandmother runs the household for the two of them as she has always done, including preparing all the meals. Your grandmother
tells you that both your grandparents have had some bowel "irregularity" lately and asks you to recommend a laxative. Based on
your knowledge of the alimentary tube, what information would you collect and what advice would you give her?
When you have completed the study activities to your satisfaction, retake the mastery test and compare your performance with
your initial attempt. Ifthere are still areas you do not understand, repeat the appropriate study activities.
188