THE DIGESTIVE SYSTEM

 

I. GROSS ANATOMY:  Locate the following structures on the x-rays, preserved cat, and on the various torso models available.  Digestive Models


   A. oral cavity

        1. tongue

            a. circumvallatepapillae

            b. fungiform papillae

            c. filiform papillae

            d. lingual and palatine tonsil

        2. teeth (incisors, canines, premolars, molars)

            a. crown

            b. neck

            c. root

            d. enamel

            e. dentin

            f. cementum

            g. pulp cavity

            h. dental caries

            i.  root canal

            j. apical foramen

        3. hard and soft palates
   B. salivary glands

        1. parotid gland

        2. submandibular gland

        3. sublingual gland
   C. pharynx (nasopharynx, oropharynx, and laryngopharynx)
   D. esophagus
   E. esophageal hiatus (in diaphragm)
   F. stomach

        1. cardiac sphincter (Gastroesophageal sphincter)

        2. greater curvature (with greater omentum)

        3. lesser curvature (lesser omentum not visible)

        4. cardiac region, fundus, body, pyloric region

        5. rugae

        6. gastric ulcer
   G. pyloric sphincter
   H. small intestine
        1. duodenum
        2. jejunum
        3. ileum
        4. hepatopancreatic ampulla and sphincter of Oddi

        5. plicae circularis

        6. villi (with artery, vein, and lacteal)

        7. mesentery
   I. ileocecal valve
   J. large intestine (colon)
      1. cecum
      2. appendix
      3. colon:  ascending, transverse, descending, sigmoid portions
      4. rectum
      5. tenia coli
      6. haustra
      7. internal and external anal sphincter
   K. liver (lobes: right , left, caudate, quadrate; falciform ligament; hepatic duct and common bile duct)
   L. gall bladder with cystic duct
   M. pancreas with pancreatic duct

 

II. HISTOLOGY:  Examine the following slides and learn to recognize the structures listed. HISTOPICS
    A. Tongue--papilla, taste buds, stratified squamous epithelium, skeletal muscle
    B. Stomach--mucosa, submucosa, muscularis externa, serosa, cardiac region, body, gastric pits, simple columnar epithelium, gastric glands, smooth muscle, rugae 
    C. Gall bladder--simple columnar epithelium, rugae, smooth muscle,
    D. Small intestine--mucosa, submucosa, muscularis externa, serosa, duodenum, jejunum, ileum, simple columnar epithelium, goblet cells, villi, lumen, plicae    circularis, Brunner's glands, Peyer's patches, smooth muscle,  

    E.  Pancreas--acinar cells containing digestive enzymes, islets of Langerhan's

    F.  Liver (visible on the gallbladder slide)-- lobules, central vein, sinusoidal capillaries
 
FOR THE PRACTICAL, BE ABLE TO IDENTIFY THE STRUCTURES ABOVE (both Gross and Histological) AND GIVE A FUNCTION OF EACH.  BE ABLE TO INDICATE THE ROLE OF THE STRUCTURE IN CHEMICAL OR MECHANICAL DIGESTION.
 
III. CAT DISSECTION: Use the provided cat dissection to identify the appropriated digestive organs.

   A.  Cat Dissection List:  See if you can identify some of the following structures from the cat dissection.  All may not be visible!

    B.  Quiz Yourself

IV. PHYSIOLOGY: In order to study results of chemical digestion, sample food items from major food groups will be available to you.  You will expose these samples to a variety of simulated digestive juices as follows, and observe the results.  In this way you are studying chemical digestion in vitro (in the test tube) instead of in vivo (in the organism).  Much of our knowledge of physiology and biochemistry has come from such controlled experiments in simulated conditions.

 A. Food samples:
     1. cooked egg albumen (a protein)
     2. starch (a carbohydrate)
     3. vegetable oil (a fat)

 B. Procedure:
      1. At sign reading "Protein Digestion--Do NOT shake tubes" 
          a. "Protein and Water"
          b. "Protein and Oral Juice"
          c. "Protein and Stomach Juice"
          d. "Pepsin solution, no HCl" (Simulating Stomach Juice without HCl)
          e. "Protein and Pancreatic Juice"
 

STUDENT ACTIVITY for PROTEIN DIGESTION: EXAMINE THE ABOVE TUBES (1a, 1b, 1c, 1d, and 1e) AND MAKE WRITTEN DESCRIPTIONS OF YOUR OBSERVATIONS.   

      a.

      b.

      c.

      d.

      e.

ANSWER THESE QUESTIONS:

      1. WHICH TUBE(S) SHOW(S) EVIDENCE OF CHEMICAL BREAKDOWN OF
             THE PROTEIN  IN THE EGG WHITE? HOW CAN YOU TELL? 

 

        2. WHY IS TUBE "d" NOT AN ACCURATE SIMULATION OF GASTRIC
            JUICE?  HOW DID THE  RESULTS OF THIS TUBE COMPARE TO TUBE
            "c"?  WHAT IS THE ONLY DIFFERENCE  BETWEEN THE CONTENTS OF
            "c" AND "d"?  IS LOW PH NECESSARY FOR PROTEIN  DIGESTION? 

 

        3. WHY IS IT NECESSARY TO INCLUDE TUBE "a" IN THIS SERIES,
            CONTAINING ONLY  WATER AND EGG WHITE?


 
      4. WHY IS THE INCUBATION PERIOD NECESSARY?  WHY IS THE
        TEMPERATURE FOR  INCUBATION REQUIRED TO BE 37 DEGREES C? 

 

 
 

      2. At a sign reading "Starch Digestion"
           a. "Starch Solution and Water"
           b. "Starch Solution and Oral Juice"
           c. "Starch Solution and Stomach Juice"
           d. "Starch Solution, Pepsin, pH 7" (Simulating Stomach Juice without HCl)
           e. "Starch Solution and Pancreatic Juice"
           f. 1 dark dropper bottle of I-KI (iodine-potassium iodide)
           g. 1 spot plate
 

STUDENT ACTIVITY for STARCH DIGESTION:  EXAMINE TUBES 2a, 2b, 2c, 2d, and 2e  for the presence of starch by the following method.  Transfer a sample from each tube into a separate depression on a spot plate. (Be sure to keep a record of which solution is placed in which section of the plate, or perform the tests one at a time, rinsing and drying the plate between tests.)  Add one drop of iodine-potassium iodide to each depression.  Observe and record the results.  Note that a reaction will occur between the I-KI and starch producing a deep blue or purplish color.  Fill out this chart:
 
        Contents of Bottle      Color after I-KI added        Presence of Starch (Y or N)
2a:
 		    
2b:
 		    
2c:
 		    
2d:
 		    
2e:
 		    

ANSWER THESE QUESTIONS:

    1. BY EXAMINING YOUR RESULTS, DETERMINE WHICH SOLUTIONS
        SHOW EVIDENCE OF STARCH BREAKDOWN.


     
    2. HOW DID YOU MAKE THIS DETERMINATION?


     
    3. WHERE IN THE BODY DOES STARCH BREAKDOWN BEGIN?


     
    4. WHAT ENZYME IS ACTIVE IN STARCH BREAKDOWN?


     
    5. IN WHICH MAJOR ORGANIC CATEGORY DOES STARCH BELONG?


     

    

      3. At a sign reading "Fat Digestion" a test tube rack with:
           a. "Oil and Water"
           b. "Oil and Bile Duct Juices" (containing bile salts)
  

STUDENT ACTIVITY for FAT DIGESTION: While holding the stoppers with your finger, shake each tube and return to its place in the test tube rack.  Observe continually and answer the following questions:
    1. WHAT HAPPENS TO THE CONTENT OF EACH TUBE AFTER 10 SECONDS?



    2. AFTER 1 MINUTE?



    3. AFTER 5 MINUTES?



    4. DOES EACH TUBE STILL CONTAIN THE SAME AMOUNT OF OIL?


     
    5. INTERPRET WHAT THIS MEANS IN REGARD TO THE POSSIBLE ROLE
        OF BILE DUCT JUICE  IN THE DIGESTION OF OIL.


     

   

FOR THE LAB PRACTICAL, SAMPLE TUBES FROM THE VARIOUS DEMONSTRATIONS MAY BE SET UP AT A TEST STATION.  BE ABLE TO ANSWER THE QUESTIONS ABOUT THE TUBES.  THESE QUESTIONS WILL BE DRAWN FROM THE QUESTIONS ASKED WITHIN THIS EXERCISE.  ALSO, BE ABLE TO NAME THE NORMAL BODY SOURCE OF EACH OF THE DIGESTIVE JUICES SIMULATED.