Teacher's Guide for Fetal Pig Dissection

Student Worksheet: Fetal Pig Dissection | Also can be downloaded in .doc format

These sections have additional notes and guidance. Some things to consider before you start the lab.

1. Do you have space with a sink? Pigs are a lot more involved than frogs and the preservatives will need to be drained and pigs rinsed. This is not a good dissection for classrooms that do not have sinks.

2. Have your students completed the frog dissection? The pig is more advanced, students should have a basic understanding of dissection protocols.

3. Pigs will need to be ordered from a biological supply company. If they are not injected, the circulartory system is very difficult to view. Generally, 1 pig for two students is a good match, but you could get away with 3-4 students per pig.

4. Safety: Goggles are required for all dissections. Latex gloves are optional, though generally preferred. Students should always wash hands even if they wore gloves. Many chemicals will seep through the latex. I have switched to nitrile gloves because it provides more of a barrier from harsh chemicals, but they are slightly more expensive.

5. Assessment. I take a grade on the completion of this lab guide. But as worksheets go, you do want the students to work out the answers together and ask for help when needed. Generally I use a quick and easy method to grade it. Each section is worth 5 pts. If its completed and looks mostly right, then they get the full 5 pts. Reduce pts if there are blanks or incorrect answers.

The biggest part of their grade comes from the LAB PRACTICAL. This is where pigs are set up at stations with numbered or colored tags in the structures. Students have 1 minute at each station to identify the structure and write it on their answer sheet. This is done in complete silence with no working together. Depending on the class, I may or may not allow them a word bank. Honors classes do not get a word bank usually unless I have an IEP or student that needs differentiation. The sheets below can be printed for the practical, they are numbered 1-50, though you don't need to use all of the blanks. Just make sure your practical contains enough stations to keep students busy. If you have 30 students, you can have 25 stations with questions, and 5 "rest stations" interspersed.

Lab Practical Blanks | .doc file

Also print out the fetal pig lab guide - this just lists all of the structures they need to find with a checkbox. It makes for a good reference and study guide.

Fetal Pig Dissection: External Anatomy

External Anatomy

1. Determine the sex of your pig by looking for the urogenital opening. On females, this opening is located near the anus. On males, the opening is located near the umbilical cord. Check the bags and packaging, they are often labeled with the pig's sex. Make sure you mix them up within the classroom.

If your pig is female, you should also note that urogenital papilla is present near the genital opening. Males do not have urogenital papilla.

Both males and females have rows of nipples, and the umbilical cord will be present in both.
What sex is your pig? _________

2. Make sure you are familiar with terms of reference: anterior, posterior, dorsal, ventral. In addition, you'll need to know the following terms

Medial: toward the midline or middle of the body
Lateral: toward the outside of the body
Proximal: close to a point of reference
Distal: farther from a point of reference

*label the sides on the pig picture above. On the pig picture, they should just labe the anterior, posterior, dorsal, ventral.

3. Open the pig's mouth and locate the hard and soft palate on the roof of the mouth. Can you feel your own hard and soft palates with your tongue?

Note the taste buds (also known as sensory papillae) on the side of the tongue. Locate the esophagus at the back of the mouth. Feel the edge of the mouth for teeth. Does the fetal pig have teeth? _yes
Are humans born with teeth? ___ no _

Locate the epiglottis, a cone-shaped structure at the back of the mouth, a flap of skin helps to close this opening when a pig swallows. The pharynx is the cavity in the back of the mouth - it is the junction for food (esophagus) and air (trachea). To find the epiglottis, you will need to make deep cuts at the edges of the mouth, I also place a lot of pressure on the jaw to break it and to get the mouth to fully open. Students will often be too gentle opening the mouth.

4. Gestation for the fetal pig is 112-115 days. The length of the fetal pig can give you a rough estimate of its age.
11mm - 21 days | 17 mm - 35 days | 2.8 cm - 49 days
4 cm - 56 days | 22 cm - 100 days | 30 cm -- birth

5. Observe the toes of the pig. How many toes are on the feet? _________________
Do they have an odd or even number of toes? ______odd toed - artiodactyls_________________

6. Observe the eyes of the pig, carefully remove the eyelid so that you can view the eye underneath. Does it seem well developed? Do you think pigs are born with their eyes open or shut? _____________eyes developed, they usually open their eyes within first day__________________

7. Carefully lay the pig on one side in your dissecting pan and cut away the skin from the side of the face and upper neck to expose the masseter muscle that works the jaw, lymph nodes, and salivary glands. The salivary glands kind of look like chewing gum, and are often lost if you cut too deeply. Salivary glands are usually in the same spot, near the cheek and jaw. Lymph nodes can be in different spots and be difficult to locate.

**Make sure you know the locations of all the bold words on this handout**

incisions

The Anatomy of the Fetal Pig (internal)

In this activity, you will open the abdominal and thoracic cavity of the fetal pig and identify structures. Remember, that to dissect means to "expose to view" - a careful dissection will make it easier for you to find the organs and structures. Be sure to follow all directions.

The Incision

Place your fetal pig in the dissecting pan ventral side up. Use string to "hog-tie" your pig so that the legs are spread eagle and not in your way. Use scissors to cut through the skin and muscles according to the diagram. Do not remove the umbilical cord. In the first section, you will only examine the abdominal cavity (the area below the ribcage).

After completing the cuts, locate the umbilical vein that leads from the umbilical cord to the liver. You will need to cut this vein in order to open up the abdominal cavity.

Your pig may be filled with water and preservative, drain over the sink if necessary and rinse organs. Locate each of the organs below, check the box

1. Diaphragm. This muscle divides the thoracic and abdominal cavity and is located near the ribcage.
The diaphragm aids in breathing. checkbox
2. Liver. This structure is lobed and is the largest organ in the body. The liver is responsible for making bile for digestion. checkbox
3. Gall bladder. This greenish organ is located underneath the liver; the bile duct attaches the gall bladder to the duodenum. The gall bladder stores bile and sends it to the duodenum, via the bile duct. checkbox
4. Stomach. A pouch shaped organ that rests just underneath and to the pig's left. At the top of the stomach, you'll find the esophagus. The stomach is responsible for churching and breaking down food. checkbox
5. At each end of the stomach are valves that regulate food entering and leaving the stomach. At the esophagus is the cardiac sphincter valve, and at the duodenum is the pyloric sphincter valve. View the inside of the stomach by slicing it open lengthwise. checkbox
6. The stomach leads to the small intestine, which is composed of the duodenum (straight portion just after the stomach) and the ileum (curly part). checkbox
7. The ileum is held together by mesentery. In the small intestine, further digestion occurs and nutrients are absorbed through the arteries in the mesentery. These arteries are called mesenteric arteries.checkbox
8. Pancreas: a bumpy organ located along the underside of the stomach, a pancreatic duct leads to the duodenum. The pancreas makes insulin, which is necessary for the proper uptake of sugars from the blood.checkbox
9. Spleen: a flattened organ that lies across the stomach and toward the extreme left side of the pig. The spleen stores blood and is not part of the digestive system. On the underside of the spleen, locate the splenic artery. checkbox
10. At the end of the ileum, where it widens to become the large intestine, a "dead-end" branch is visible. This is the cecum. The cecum helps the pig digest plant material. checkbox
11. The large intestine can be traced to the rectum. The rectum lies toward the back of the pig and will not be moveable. The rectum opens to the outside of the pig, or the anus. The large intestine reabsorbs water from the digested food, any undigested food is stored in the rectum as feces.checkbox
12. Lying on either side of the spine are two bean shaped organs: the kidneys. The kidneys are responsible for removing harmful substances from the blood, these substances are excreted as urine. (more on this later) checkbox
13. Two umbilical vessels can be seen in the umbilical cord, and the flattened urinary bladder lies between them.checkbox

Identify the structures on the diagram.

1. _____esophagus___

2. _____liver_______________

3. _____gall bladder_________

4. ____bile duct___________

5. ____stomach____________

6. ____duodenum_____________

7. ____pancreas______________

8. ____small intestine_______

9. ____spleen_____________

10. ___cecum_____________

11. ___large intestine__________

12. ___rectum_____________

13. ___umbilical arteries__________

pig diagram

Identify the organ (or structure)

14. _____pyloric sphincter valve____ Opening (valve) between stomach and small intestine.
15. _____gall bladder_____________ Stores bile, lies underneath the liver.
16. ___________cecum___________ A branch of the large intestine, a dead end.
17. ___________diaphragm________ Separates the thoracic and abdominal cavity; aids breathing.
18. ________mesentery___________ Membrane that holds the coils of the small intestine.
19. ________duodenum___________ The straight part of the small intestine just after the stomach.
20. _______bile duct______________ Empties bile into the duodenum from the gall bladder.
21. _______rectum_______________ The last stretch of the large intestine before it exits at the anus.
22. _______pancreas_____________ Bumpy structure under the stomach; makes insulin
23. _______bladder_______________ Lies between the two umbilical vessels.

Urinary and Reproductive Systems

1. Locate the kidneys; the tubes leading from the kidneys that carry urine are the ureters. The ureters carry urine to the urinary bladder - located between the umbilical vessels. To find the ureters, expose the kidney and wiggle it, the ureter is attached and you'll see it move.
2. Lift the bladder to locate the urethra, the tube that carries urine out of the body. checkbox
3. Note the vessels that attach to the kidney - these are the renal vessels checkbox

Male
1. Find the scrotal sacs at the posterior end of the pig (between the legs), testis are located in each sac. Open the scrotal sac to locate the testis. checkbox
2. On each teste, find the coiled epididymis. Sperm cells produces in the teste pass through the epididymis and into a tube called the vas deferens (in humans, a vasectomy involves cutting this tube).checkbox
3. The penis can be located by cutting away the skin on the flap near the umbilical cord. This tube-like structure eventually exits out the urogenital opening, also known as the urethra. checkbox The penis of the fetal pig is actually pretty difficult to find because it is internal (this can lead for much hilarity in the lab as students try to locate the structure. A simple technique I use to find it is to find the area just behind the urethral opening and roll this area (its also where the umbilical arteries are attached) between the thumb and forefinger. You should feel a solid tube like structure just under the skin - this is the penis.

Female
4. In the female pig, locate two bean shaped ovaries located just posterior to the kidneys and connected to the curly oviducts. checkbox
5. Trace the oviducts toward the posterior to find that they merge at the uterus. Trace the uterus to the vagina. The vagina will actually will appear as a continuation of the uterus. checkbox

LABEL THE DIAGRAMS

urinary system femalemale

Dissection of the Thoracic Cavity

You may need to cut through the pig's sternum and expose the chest cavity (thoracic cavity) to view. You will need to cut all the way up into the pig's neck, almost to the chin and open the thoracic cavity. Identify each of the following organs.

1. Find the diaphragm again. Remember that the diaphragm separates the abdominal cavity from the thoracic cavity and it aids in breathing. Above the diaphragm, center of chest, is the heart. checkbox
2. Remove the pericardium, which is a thin membrane that surrounds the heart checkbox.
3. The structures visible on the heart are the two atria (12,13), the ventricle (14) which has two chambers not visible from the outside. checkbox
4. The most obvious vessel on the front of the heart is the pulmonary trunk (1) . It curves upward and joins the aorta (2) - a vessel which arches from the heart and curves around to go to the lower part of the body -where it is called the abdominal (dorsal) aorta (9). The aorta supplies the body with blood. checkbox
5. The aorta will curve back and then branch in two spots - the right brachiocephalic (3) and the left subclavian (5) checkbox
6. The right brachiocephalic then branches into arteries - the common carotid (4) and the right subclavian (10) The subclavians supply blood to the arms and follow the clavicle bone checkbox
7. The common carotid (4), which will branch into the left (7) and right carotid arteries (8). The carotid arteries supply blood to the head and neck. checkbox
8. Observe the coronary vessels (6) on the outside of the heart - these vessels supply blood to the muscle of the heart. checkbox
9. Easy arteries to find are the ones that run near the ribs. These are the intercostal arteries (11). checkbox
10. Lift the heart to look on its dorsal side (toward the back), you should be able to see the anterior and posterior vena cava, which brings blood from the body back to the heart. In addition, you should also be able to find the left and right jugular veins that drain blood from the head and run parallel to the carotids.checkbox
circulatory system
11. Push the heart to the side to locate two spongy lungs located to the left and right side. The lungs are connected to bronchial tubes (not visible) which connect to the trachea (forming a Y). checkbox
12. The trachea is easy to identify due to the cartilaginous rings, which help keep it from collapsing as the animal inhales and exhales. The trachea should be located in the chin area above the heart. checkbox
13. Lying atop the trachea, locate the pinkish-brown, V shaped structure called the thyroid gland. This gland secretes hormones that control growth and metabolism. checkbox
14. At the anterior (toward head) of the trachea, you can find the hard light colored larynx (or voice box). The larynx allows the pig to produce sounds - grunts and oinks. checkbox

Identify by number:


Aorta __2__ Dorsal Aorta _9__Pulmonary Trunk _1_
Common carotid _4__ Left & Right Carotid _7,8__
Coronary vessels _6__ Left Subclavian__5__
Right Subclavian __10__ Right Brachiocephalic _3___
Right Atrium __12__ Left Atrium _13__
Intercostal __11___ Ventricle __14_

Identify the structure.

1. _______pericardium________ Membrane over the heart.
2. _____trachea________ Airway from mouth to lungs
3. ____carotids_______ Blood supply to head
4. ____ventricles_________ Lower heart chambers
5. ____dorsal aorta_______ Blood supply to lower body
6. ____diaphragm_______ Muscle to aid breathing
7. ____vena cava_______ Returns blood to heart
8. ____aorta (or pulmonary)____ Large vessel at top of heart
9. ____larynx______ Used to make noises
10. ___coronary______ Arteries on heart surface.

Fetal Pig - Dissection of the Lower Arteries

I often do this part as an "optional section". Some students will work very fast and will need something to do while others catch up. I have also offered extra credit to students who can expose these arteries to view (cleanly), which gives them extra incentive to work on it. The problem is, if you are spending time with groups that are farther behind, then you don't have a lot of time to help students with the arteries. Giving them extra credit encourages them to try, but also requires them to work on their own.

1. Trace the abominal aorta (also called the dorsal aorta) to the lower part of the body, careful tweezing of the tissue will reveal several places where it branches, though some of the arteries may have been cut when you removed organs of the digestive system. checkbox
2. The hepatic artery leads to the liver. (may not be visible) checkbox
3. The splenic artery leads to the spleen (may not be visible) checkbox
4. The renal arteries lead to the kidney. checkbox
5. The mesenteric artery leads to the mesentery and branches into many smaller vessels. Look in the small intestine to find this artery. checkbox
6. Trace the abominal aorta and note where it joins the umbilical arteries. You will need to cut the muscle in the leg to trace the next vessels. Use a pin to carefully tease away the surrounding muscle and tissue. checkbox
7. The abominal aorta splits into two large vessels that lead to each leg - the external iliac arteries will turn into the femoral arteries as they enter the leg checkbox
8. Follow the umbilical artery toward the pig, you'll find that it branches and a small artery stretches toward the posterior of the pig - this is the ilio-lumbar artery. checkbox
9. Follow the external iliac into the leg (carefully tease away muscle),it will branch into two arteries: the femoral (toward the outside of the leg) and the deep femoral (toward the back of the leg) checkbox

lower arteries

flow chart