Anatomy and physiology labs

EXPERIMENT 3: FETAL PIG DISSECTION - ENDOCRINE SYSTEM Like many other systems, the endocrine system of the fetal pig provides a good representation of the anatomy of the human endocrine system. This experiment will guide you through an exploration of the larger endocrine system glands.

PROCEDURE 1. To begin, lay down your underpad and place your dissecting tray on top of it. Be sure you have all of your safety equipment

on before beginning.

2. Once prepared, gently open the bag your pig is in.

Note: DO NOT destroy this bag or empty out the preserving solution within the bag. You will need it for the whole semester.

3. Lay your pig onto the dissecting tray, ventral side facing up. Slide the strings over the dissection tray to hold the pig in place.

4. To view the internal anatomy of the fetal pig, it is necessary to cut through the muscle covering the body. If your lab kit includes The Muscular System lab, you have already completed these incisions and simply need to peel back the skin flaps and pin them to your dissection tray. If you have not completed these incisions, follow steps 5 – 9 using Figure 7.

Experiment 3Fetal Pig Dissection - The Endocrine System Materials Fetal Pig

Dissection Tray

Dissection Tools

String (attached to pig’s hooves)

Experiment Inventory

Figure 7: Cut lines for exposing the body cavity of the fetal pig.

5. Incision 1: Using the forceps, grasp the umbilical cord tightly. While pulling upward on the umbilical cord, use a scalpel or dissecting scissors to make an incision along the mid-ventral line of the body, starting about 1 cm superior to the umbilical cord and continuing to the upper portion of the throat. Then, make a circular incision around the umbilical cord.

Note: Always cut away from your body when possible. Use appropriate force to ensure you cut through only the muscle and do not puncture internal organs. It is better to go back and retrace your incision than to cut too deeply.

6. Incision 2: The inferior incision will depend on the sex of our specimen. See Figure 7 for the appropriate cuts for male (2M) and female (2F) pigs.

7. Continue to deepen incisions 1 and 2 until the body cavity, or coelom, is exposed.

8. Incision 3, 4, 5: To fully open the body cavity, make lateral incisions on either side of the mid-ventral incisions. Make the following incisions:

• V-shape at shoulder level (Incision 3).

• U-shaped across the hindlimbs connecting with Incision 2 (Incision 4).

• Lower edge of the ribs following the contour of the ribcage (Incision 5).

9. Use the scalpel and forceps to free the muscle from the thoracic cage.

10. After making these incisions, you should be able to peel back the four thoracic flaps on either side of the mid-ventral line.

Note: Do not peel back the pelvic flap. This must be kept intact for future dissections of muscle to reveal the underlying organs. Pin the flaps of muscle to your dissecting tray mat.

11. Use a dissecting scissor to cut through the ribcage.

Note: The ribs of the fetal pig are not fully developed and can be separated with a sharp blade. Use extreme caution as to not damage the underlying internal organs.

12. Examine the coelom (the fluid-filled sac that contains the organs) of the fetal pig. You will notice coelomic fluid surrounding the internal organ, lubricating them.

13. Observe the mesenteries. These thin sheets of connective tissue suspend the organs and hold them in place.

14. A large muscular structure called the diaphragm divides the body cavity into two parts: the thoracic cavity and the abdominal cavity. Use your scalpel to free the diaphragm from the connective tissue, but do not remove it.

15. The thyroid gland of the fetal pig is located inferior to the larynx, along the trachea.

Note: You may have to lift the thymus to view the thyroid gland. It is a small, reddish, bilaterally symmetric mass.

16. Locate the pancreas, an elongated, granular mass positioned between the stomach and the small intestines. You will not be able to see the Islets of Langerhans, but remember their importance in secreting insulin and glucagon.

17. Take a picture of your pig’s exposed pancreas for the upload document. Make sure your name and access code are handwritten on a piece of paper that is clearly visible in the background of the photograph.

18. The crescent-shaped adrenal gland is located on the superiomedial margin of each kidney. These glands appear lighter in color than the kidneys; however, they may be difficult to see. The layers of this gland are responsible for secreting glucocorticoids (middle cortex), androgens (inner cortex), and neurotransmitters (adrenal medulla).

19. To finish, locate the bag the pig came in. Gently place the pig back into the bag, and tightly secure the bag with a rubber band, or place the pig in the zip-seal bag provided in the dissection box.

20. Place the pig back into the cool environment you had previously stored it in. Remember, the best place to keep the pig is in a cool, dark place.

21. After your pig has been put away, clean off your dissecting tray and dissecting tools with soap and water. Biological scraps should not be thrown into the garbage. Securely store the biological scraps until the end of the term so that they can be properly disposed of at one time.

22. Clean the area in which you worked with soap and water. As long as the underpad has not been damaged, keep it for future experiments.