Organs of the Digestive System
Background
The digestive system includes the organs associated with the alimentary canal and several accessory
structures. The alimentary canal, which is a muscular tube, passes through the body from the opening of
the mouth to the anus. It includes the oral cavity, pharynx, esophagus, stomach, small intestine, and large
intestine. The canal is adapted to move substances throughout its length. It is specialized in various
regions to store, digest, and absorb food materials and to eliminate the residues. The accessory organs,
which include the salivary glands, liver, gallbladder, and pancreas, secrete products into the alimentary
canal that aid digestive functions.
Materials Needed
Textbook
Human torso model
Skull with teeth
Compound light microscope
Prepared microscope slides of the
following:

Liver

Tongue

Stomach (fundic)

Pancreas

Small intestine (jejunum)

Large intestine (colon)
Purpose of the Exercise
Review the structure and function of the digestive organs and examine the tissues of these organs
microscopically.
Procedure A – Mouth and Salivary Glands
1. Label figures 49.1, 49.2, and 49.3.
2. Examine the mouth of the human torso model and the skull to locate the following structures: oral
cavity, vestibule, tongue, lingual tonsils, palate, palatine tonsils, pharyngeal tonsils (adenoids),
gums (gingivae), teeth.
3. Examine a tooth model and locate the following features: crown, neck, root.
4. Observe the head of the torso and locate the following: parotid salivary gland, parotid duct,
submandibular salivary gland, submandibular duct, sublingual salivary gland.
5. Examine a microscopic section of the liver, using low and high-power magnification.
6. Complete Part A of the laboratory report.
Procedure B – Pharynx and Esophagus
1. Label figure 49.4.
2. Observe the human torso model and locate the following features: pharynx, epiglottis, esophagus,
lower esophageal sphincter (cardiac sphincter).
3. Have your partner take a swallow from a cup of water. Carefully watch the movements in the anterior
region of the neck. What steps in the swallowing process did you observe?
4. Examine a microscopic section of the tongue, using low-power magnification. Note that layers of
muscle tissue in the wall. Locate some mucous glands in the submucosa. They appear as clusters of
lightly stained cells.
5. Complete Part B of the laboratory report.
Procedure C – The Stomach
1. Label figures 49.5 and 49.6.
2. Observe the human torso model and locate the following features: rugae, cardiac region, fundic
region, body region, pyloric region, pyloric canal, pyloric sphincter, lesser curvature, greater
curvature.
3. Examine a microscopic section of the stomach wall, using low-power magnification. Note how the inner
lining of simple columnar epithelium dips inward to form gastric pits. The gastric glands are tubular
structures that open into the gastric pits. Near the deep ends of these glands, you should be able to
locate some intensely stained (bluish) chief cells and some lightly stained (pinkish) parietal cells. What are
the functions of these cells?
4. Complete Part C of the laboratory report.
Procedure D – Pancreas and Liver and Gallbladder
1. Label figure 49.7.
2. Observe the human torso model, liver model, and pancreas model and locate the following structures:
pancreas, pancreatic duct, liver, round ligament, falciform ligament, coronary ligament,
gallbladder, hepatic ducts, common hepatic duct, cystic duct, common bile duct, hepatopancreatic
sphincter.
3. Examine the pancreas slide, using low-power magnification. Observe the exocrine cells that secrete
pancreatic juice.
4. Complete Part D of the laboratory report.
Procedure E – Small and Large Intestines
1. Observe the human torso model and locate each of the following features: small intestine, mesentery,
ileocecal sphincter, large intestine, anal sphincter muscles, anus.
2. Using low-power magnification, examine a microscopic section of the small intestine wall. Identify the
mucosa, submucosa, muscular layer, and serosa.
Note the villi that extend into the lumen of the tube. Study a single villus, using high-power magnification.
Note the core of connective tissue and the covering of simple columnar epithelium that contains some
lightly stained goblet cells. What is the function of the villi?
3. Examine a microscopic section of the large intestine wall. Note the lack of villi. Also note the tubular
mucous glands that open on the surface of the inner lining and the numerous lightly stained goblet cells.
Locate the four layers of the wall. What is the function of the mucus secreted by these glands?
4. Complete Part E of the laboratory report.
Critical Thinking Application
How is the structure of the small intestine better adapted for absorption than the large intestine?
Figure 49.1 Label the major features of the oral cavity.
Figure 49.2 Label the features associated with the major salivary glands.
Figure 49.3 Label the features of this cuspid tooth.
Figure 49.4 Label the organs of the digestive tract.
Figure 49.5 Label the major regions of the stomach and associated structures.
Figure 49.6 Label the lining of the stomach.
Figure 49.7 Label the features associated with the liver, gallbladder, and pancreas.
Part A
Match the structures in column B with the descriptions and functions in column A.
Place the letter of your choice in the space provided.
Column A
Column B
___ 1. Bonelike substance beneath tooth enamel
a. Cheeks
___ 2. Smallest of major salivary glands
b. Amylase
___ 3. Tooth specialized for grinding
c. Crown
___ 4. Chamber between tongue and palate
d. Dentin
___ 5. Projections on tongue surface
e. Frenulum
___ 6. Cone-shaped projection of soft palate
f. Incisor
___ 7. Lateral boundaries of oral cavity
g. Molar
___ 8. Attaches tooth to jaw
h. Oral Cavity
___ 9. Chisel-shaped tooth
i. Palate
___10. Roof of oral cavity
j. Papillae
___11. Space between the teeth, cheeks, and lips
k. Periodontal ligament
___12. Anchors tongue to floor of mouth
l. Gingivae
___13. Pink ridge around base of teeth
m. Sublingual gland
___14. Portion of tooth projecting beyond gum
n. Uvula
___ 15. Splits starch into disaccharides
o. Vestibule
Part B
Complete the following:
1. The part of the pharynx superior to the soft palate is called the _____________________.
2. The middle part of the pharynx is called the ___________________________.
3. The inferior portion of the pharynx is called the _________________________.
4. The auditory tube opens through the wall of the ________________________.
5. Swallowing is also called __________________________.
6. The esophagus passes through the mediastinum posterior to the ____________ as it descends into the
thorax.
7. The esophagus is lined with ___________________________ epithelium.
8. The esophagus penetrates the diaphragm through an opening called the _______________________.
9. Summarize the functions of the esophagus.
Part C
Complete the following:
1. Name the four regions of the stomach.
2. Name the valve that prevents regurgitation of food from the small intestine back into the stomach.
3. Name the three types of secretory cells found in gastric glands.
4. Name the gastric cells that secrete digestive enzymes.
5. Name the gastric cells that secrete hydrochloric acid.
6. Name the most important digestive enzyme in gastric juice.
7. Name a substance needed for efficient absorption of vitamin B12.
8. Name a hormone secreted by the stomach that inhibits gastric glands secretion.
9. Name the semifluid paste of food particles and gastric juice.
10. Summarize the functions of the stomach.
Part D
Match the structures in column B with the descriptions and functions in column A.
Place the letter of your choice in the space provided.
Column A
Column B
___ 1. Inhibits gastric secretion and motility
a. Amylase
___ 2. Stimulate production of acids and enzymes
b. Gastrin
___ 3. Targets maltose, make monosacharides
c. Cholecystokinin
___ 4. Stimulate production of pancreatic enzymes
d. Amylase
___ 5. Produces short peptide chains
e. Peptidases
___ 6. Stimulate release of insulin
f. Gastric inhibit Peptide
___ 7. Targets complex carbohydrates
g. Pepsin
___ 8. Produces amino acids
h. Maltase
___ 9. Targets triglycerides, forming monoglycerides
i. Secretin
___10. Enzyme produced in stomach
j. Pancreatic lipase
___11. Targets complex carbohydrates
k. Trypsin
Part E
Complete the following:
1. Name the three portions of the small intestine.
2. Describe the functions of the mesentery.
3. Name the lymphatic capillary found in an intestinal villus.
4. Name the tubular glands found between the bases of the intestinal villi.
5. Name five digestive enzymes secreted by the small intestinal mucosa.
6. Name the sphincter that controls movement of material between the small and large intestines.
7. Name the small projection that contains lymphatic tissue attached to the cecum.
8. Summarize the functions of the small intestine.
9. Summarize the functions of the large intestine.