Basics of Dissection
Objectives:· Observe organization of body systems
· Investigate structure of organs & tissues
· Explore correlation of structure and function
· Practice good dissection technique
Introduction / Background
The word dissection means “to make visible”. In this laboratory exercise you will examine the anatomy of a rat as a model for human anatomy.
All mammals, including humans and rats, are anatomically similar. The similarity of the organ systems in organization, form and function may be considered evidence of common ancestry.
Keep in mind two general ideas as you proceed with this dissection: First, the rat and human anatomy are comparable, making the rat a useful subject to study the organization of body systems. Secondly, the arrangement of the organs within the body of the rat (and human) allows efficient interaction with other components of the organ system and with other organ systems.
For the structures you will identify in this dissection, you should determine the following:
1. The organ system associated with each structure
2. How the structure interacts with other components of the organ system, as well as with other body systems
3. The function of the organ system and specific function of the structure (if applicable).
Know Your Tools
§ Dissecting pan /
§ Dissecting (T) pins /
§ Disposable pipettes
§ Forceps – Straight, curved /
Scalpel
§ Scissors /
§ Blunt probe
§ Dissecting needle
Measurements
All measurements are metric.
Since most biological specimens are irregularly shaped, here are a few “tips” to help you get accurate measurements:
Length (centimeters - cm, millimeters - mm)
Tip: If your animal is bent or twisted, stretch a piece of string from crown of the head to the base of the tail. You can then lay the string out straight for an accurate length of your specimen.
Volume – milliliters - ml / cubic centimeters – cc (1 ml = 1 cc)
Use water displacement method: Fill an appropriately sized beaker half full with water. Write down the volume. Put the organ into the beaker and note the increase in volume. Record the difference between these two measurements.
Weight (grams)
1. Zero the scale before beginning; make sure all weights on the triple beam balance are moved completely to the left.
2. Use an appropriately sized container for weighing your specimen or organ. Weigh the empty container by moving the weights on the balance. Weights must drop into slots for weight to be accurate. Record the weight of the empty container (tare weight).
3. Place the sample in the container, move the weight bars and record the weight.
4. To calculate the weight of your specimen: Subtract the tare weight of the container (step 2) from the weight you measured in step 3.
Dissection Safety Rules
§ Complete all pre-lab activities before beginning the dissection. The most important safety rule is to know what you are doing!
Preserved specimen
§ Avoid contact with chemicals used to preserve specimen. Rinse specimen completely before dissection and wear disposable gloves.
§ Wear safety goggles to prevent the splashing of any chemicals into the eyes. Know where the eye-wash fountain is if needed.
§ You may want to remove contact lenses beforeworking with chemicals or preserved dissections. Contact lenses canabsorb chemicals, causing eye irritation or damage to the lenses.
Non-preserved (fresh or frozen) specimen
§ Use caution to prevent direct contact with blood or tissues. The specimen may contain bacteria that could make you VERY sick.
§ Clean all work areas, dissecting pans, tools, and anything that may have come into contact with the specimen with disinfectant (provided).
§ Optional, but recommended: lab apron and goggles.
§ Wash hands thoroughly and use alcohol hand rub after cleaning up your work area.
General Safety Precautions when working on dissections
§ Properly pin or tie dissection specimen to dissecting pan. Do not dissect while holding specimen in your hand.
§ Handle scalpel or razor blade correctly and with extreme care. Hold a scalpel like a pencil, and cut in short motions. Always cut away from your body and away from lab partners.
§ Never ingest specimen parts. Don’t even joke about it.
§ Never remove specimens, body parts or tools from the classroom. All of the dissected material must remain in the dissecting pan during the lab.
§ Properly dispose of dissected materials in the bags provided.
§ Do not put any solid materials into the sink – no matter how small they may seem!
§ Store specimens “in progress” in special bags as directed by your teacher.
§ All group members are required to clean up the work area, including disinfecting lab tables and returning clean, dry equipment and dissecting pans.
§ Wash all equipment thoroughly, dry, and return to the box you were given when the dissection is completed. Clean up is part of the lab requirement.
§ Wash hands thoroughly and use alcohol hand rub after cleaning up your work area.
Unsafe or inappropriate behavior will result in
dismissal from the lab and a zero for this assignment.
Clean up
1. Your Specimen
Ø If you have not finished with your specimen:
Wrap your rat in wet paper towels and put it into the Ziploc bag you were given. Make sure your group is identified on the baggie. Put the rat in the plastic box in the front of the room.
Ø When you have finished all your observations:
Put your rat and all biological trash in the Ziploc bag you were given. This should be put into the black trash bag or box in the front of the room.
2. Your Tools and Workspace
Ø Keep hands away from scalpel blade! Clean your scalpel with hot soapy water, wipe your scalpel on a paper towel and place it in the box that came with it.
Ø Clean all dissecting tools with hot soapy water and rinse in the pan of bleach water provided.
Ø Dry all equipment thoroughly so tools do not rust.
Ø Return tools in the box your group was given.
Ø Clean your work area thoroughly with disinfectant.
3. Your Self
Ø If you used a dissecting apron, wipe it with disinfectant and hang to dry.
Ø Wash your hands thoroughly with warm, soapy water and dry with paper towels.
Ø Use hand sanitizer.
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