Exercise 25 - Digestive and Gas Exchange Systems

STUDENT OBJECTIVE

Students observe feeding behavior of Hydra, dissect the digestive and respiratory systems of the fetal pig, study the histology of the small intestine and lung, and observe the anatomy of gills and tracheole systems.

EQUIPMENT AMOUNT (Class of 24 with 8 groups)
Compound microscope 1/student
Dissecting microscope 1/student
Spirometers and accessories 1/group
Aquarium 1/lab


MATERIALS

Slides and coverslips 1 box/lab
Lens tissue 8 pkgs/group
Pasteur pipettes 1/student
Dissecting trays with wax 1/student
Dissecting instruments: scissors, forceps, blunt probe,
     string, razor blades or scalpel 1/student
Culture dishes 1/student
Petri dishes filled with paraffin 1/student
Hand lotion 1 bottle/lab
Spot plates for holding and washing Artemia 1/student
Pins 1 pkg/lab
Thread 1 spool/lab
Small bowls 1/student
Preserved specimens
  Fetal pigs 1/student
  Storage materials (fiber tags, string, permanent marker,
     plastic bags, garbage can-20 gal) 1/lab
Prepared slides (may be shared to reduce cost)
  Hydra, longitudinal section (Turtox#Z3.131)* 1/student
  Mammalian small intestine, cross section (Turtox# Z17.22) 1/student
  Mammalian lung (CBS#7745)* Demonstration
Living specimens
  Hydra 1/student
  Crayfish 1/group
  Artemia (brine shrimp) or Daphnia cultures 1 culture/lab
  Crickets, grasshoppers, or roaches 1/student

SOLUTIONS

India ink
10 mM and 100 mM glutathione (Sigma)*
Carbon dioxide source
Saline (0.7% NaCl)

PREPARATION

Four Weeks before Lab

Fetal pigs, Hydra, Daphnia, and crayfish should be ordered for arrival one week prior to lab.

One Week before Lab

  1. Stock glutathione preparation:
    a. 100 mM glutathione 3.1 g glutathione/distilled water to make 100 ml
    Dissolve in water.
    b. 10 mM glutathione preparation:
    Take 10 ml of 100 mM glutathione and dilute to 100 ml.

  2. An aquarium should be set up to accommodate the crayfish the week before the lab.

  3. Make small dissecting dishes by melting household paraffin over boiling water and pouring into petri dishes until half filled. When the wax solidifies, cover and store until needed. These dishes can be reused in later labs.

  4. Saline preparation:

    Dissolve 1.4 g NaCl in 199 ml water.

NOTES

  1. Wax that is pitted with holes in dissection pans can be restored to a smooth finish by fanning the surface with a Bunsen burner.

  2. Hand lotion should be provided for the students in exercises that use formalin and require an inordinate amount of hand washing.

  3. Any culture dish (soft glass) that has had formalin in it, should be acid washed before any live cultures are added.

  4. Place insects in a freezer for 30 to 45 minutes to anesthetize. Alternatively, a stream of carbon dioxide from a gas cylinder directed into a 125 ml flask can be used.

CLASSROOM SUGGESTIONS

  1. Students should write their names on fiber tags with soft pencil or permanent ink marker and attach the tags to the back legs of the fetal pigs. Pigs can then be slipped into plastic bags and stored in a sealed plastic garbage pail. Separate pails can be used for different lab sections.

  2. Minimum homework would be a short essay comparing incomplete and complete digestive systems or lung and tracheole gas exchange systems.

ANSWERS TO CRITICAL THINKING QUESTIONS

  1. The extremely long trachea contains a large volume of "dead" air-air that is not involved in gas exchange. To move this large volume of air, the giraffe has oversized lungs.

  2. All the structures involved in chewing-the lips, tongue, teeth, hard palate.
    Muscles responsible for peritalsis-smooth muscle of esophagus, stomach wall, and small intestine.

SUPPLEMENTAL MATERIALS

Bio Sci II, videodisc--contains pictures of dissected fetal pig as well as histology illustrations. Dubuque, IA: Wm. C. Brown Publishers. See appendix.

Digestive System: Structure and Function, slide set. Rochester, NY: Ward's. #78WO600

Dissection of Fetal Pig, audio filmstrip set. Burlington, NC: Carolina Biological Supply. #52-5780

Respiration--External and Internal, audio filmstrip. West Los Angeles, CA: Science Software Systems, Inc. #475-0000

Respiratory System: Structure and Function, audio/filmstrip. Rochester, NY: Ward's. #78-W0630

BACK