Organs of the Digestive System Lab by MikeJenny

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									              Organs of the Digestive System
                         Laboratory Exercise 49

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
Liver model
Stomach model with pancreas
Skull with teeth
Tooth model
Compound light microscope
Prepared microscope slides of the following:
   • Parotid salivary gland
   • Esophagus
   • 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.



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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 a parotid gland, using low and high-power
   magnification. Note the numerous glandular cells arranged in clusters around
   small ducts. Also note a larger secretory duct surrounded by lightly stained
   cuboidal epithelial cells.
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 esophagus wall, using low-power
   magnification. Note that the inner lining is composed of stratified squamous
   epithelium and that there are 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.


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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. Label figure 49.8.
2. Observe the human torso model and locate each of the following features:
   small intestine, mesentery, ileocecal sphincter, large intestine, anal
   sphincter muscles, anus.
3. 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?



4. 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?



5. 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?




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Figure 49.1 Label the major features of the oral cavity.




Figure 49.2 Label the features associated with the major salivary glands.




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Figure 49.3 Label the features of this cuspid tooth.




Figure 49.4 Label the features associated with the pharynx.




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Figure 49.5 Label the major regions of the stomach and associated structures.




Figure 49.6 Label the lining of the stomach.




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Figure 49.7 Label the features associated with the liver, gallbladder, and pancreas.




Figure 49.8 Label the diagram of the digestive system.




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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. Adenoids

___ 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. Secretes the digestive enzymes in saliva       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. Serous cell

___13. Lymphatic tissue located near auditory tubes 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 _______________.



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3. The inferior portion of the pharynx is called the _______________.

4. The auditory tube opens through the wall of the _______________.

5. During swallowing, circular muscles called _______________ pull the walls of
   the pharynx inward.

6. The esophagus passes through the mediastinum posterior to the ____________
   as it descends into the thorax.

7. _______________ is the main secretion of the esophagus.

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.




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7. Name a substance needed for efficient absorption of vitamin B12.



8. Name a hormone secreted by the stomach that stimulates gastric glands to
   secrete.



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. Activates protein-digesting enzyme trypsin             a. Amylase

___ 2. Causes emulsification of fats                          b. Bile salts

___ 3. Carries on phagocytosis in liver                       c. Cholecystokinin

___ 4. Iron-storing substance in liver                        d. Enterokinase

___ 5. Carbohydrate-digesting enzyme                          e. Ferritin

___ 6. Fat-digesting enzyme                                   f. Kupffer cells

___ 7. Protein-digesting enzyme                               g. Lipase

___ 8. Stimulates gallbladder to release bile                 h. Nuclease

___ 9. Inhibits secretion of acid by parietal cells           i. Secretin

___10. Nucleic acid-digesting enzyme                          j. Somatostatin

___11. Stimulates pancreas to secrete fluids high in          k. Trypsin
       bicarbonate ions


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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.




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