• Obtain your petri dishes containing your cut planarians.
• Make observations and complete the table in Part A of the Lab Report (questions 1-21).
• Note - for Diagrams of each planarian, upload your picture in the proper place in the Lab Report.
Safety and Hygiene
1. Do not place your hands near your mouth or eyes while handling preserved specimens. Although the preservative used is non-toxic to the skin, it may cause minor skin irritations. If the preservative gets on your skin, wash immediately with soap and water.
2. If the preservative gets in your eyes, rinse thoroughly with the safety eyewash.
3. Wear lab gloves and goggles the entire time the fetal pigs are out. Even if you don't plan to touch the pig during the group dissection you need to have your gloves and goggles on.
Obtain a Fetal Pig
• Once your group has obtained a fetal pig from your instructor, remove it from the plastic bag (save the bag for later).
• Rinse off the excess preservative by holding it under running water.
• Lay the pig on its side in the dissecting pan.
• Before dissecting your fetal pig locate the umbilical cord. Examine the 3 openings in the umbilical cord. • The largest is the umbilical vein, which carries oxygenated blood from the placenta to the fetus.
• The two small openings are the umbilical arteries, which carry blood away from the fetus to the placenta.
Before you make any cuts, it is necessary to secure your fetal pig in the dissection tray.
Click here for Ward's Science Fetal Pig Visual Dissection Guide1. Place your pig in the dissection tray, ventral surface facing up. Tie one end of string to the right front limb distal to the elbow. Bring the string under the tray and back up on the left side. Tie the other end of the string distal to the left elbow. The wrists should be spread apart and under some tension. Do the same for the back limbs, tying the string just above the ankles. The legs should also be spread apart and under some tension.
2. With the scalpel, make a shallow incision below the rib cage and cut towards the tail end to 1 cm anterior (before) the umbilical cord. Refer to the diagram on Page 3 of the Ward's Science Fetal Pig Visual Dissection Guide for help making the proper cuts.
3. If you pig is female, make a complete circular cut around the umbilical cord. Continue from the cord on the midline to the anal region.
4. If your pig is male, make two incisions, one on each side of the midline to avoid cutting the penis, which lies beneath. These two incisions continue to the anal region from the arc around the cord.
5. Make a lateral incision from the umbilical cord to the groin on each side.
6. Use the diagram on Page 3 of the Ward's Science Fetal Pig Visual Dissection Guide to continue cutting open the abdominal cavity of your pig. At this point you may want to give your pig another rinse with water. Occasionally the abdominal cavity will be filled with preservative, latex, or fluid. The latex sometimes fills the cavity when blood vessels burst during the injection process. T
Try to trace the flow of blood through the fetus.
Blood enters the fetus from the oxygen rich umbilical vein.
Some blood will enter the still developing liver. The rest of the blood will bypass the mostly non-functioning liver via the ductus venosus. From there it will enter the large inferior vena cava. This will be filled with blue latex since in the adult it carries deoxygenated blood.
Blood will then enter the right atria and then bypass the right ventricle via the foramen ovale - the hole in the wall between the two atria. You will need to carefully remove the heart from the thoracic cavity and cut it open. use the coronary arteries and veins on the hearts surface as a landmark for where the wall separating the chambers is located.
Any blood that does not pass through the foramen ovale will enter the right ventricle and then the pulmonary trunk. The blood that enters the pulmonary trunk can still the bypass the pulmonary circuit via the ductus arteriosus. This is located between the pulmonary trunk and the aorta.
Blood that enters into the left atria from either the right atria or pulmonary arteries will enter into the left ventricle and then the out through the aorta.
Blood retuning from the systemic circuit leave the fetus via the paired umbilical arteries. These are located on either side of the allantoic (urinary) bladder.
• Make sure you have located all the structures listed in Part B in the Lab Report.
Clean you work area and properly return your Fetal pig
1. Lab gloves and paper towels go in the regular trash. Discarded pieces of pig go into the red plastic biohazard bag located in the laboratory room.
2. At the end of the lab put your pig back in the plastic bag and tie the bag closed.
3. Place the bagged pig in the storage tub in the front of the lab
4. Rinse the dissecting tray and stack it neatly by the sink.
5. Wipe up your station clean.
6. Clean and return your dissecting tools.
Answer the questions in Part C of your Lab Report.