You may find the following website to be very useful for reference and studying: http://www.whitman.edu/content/virtualpig
Dissection Terms
Anterior – toward the head
Posterior – toward the feet or rear
Dorsal – toward the back
Ventral – toward the front
Rostral – toward the head or nose
Caudal – toward the tail or rear
Superior – above, over, on top
Inferior – below, under
Lateral – toward the side, away from the midline
Medial – toward the midline, away from the side, in the middle
Sagittal Plane – divides body into right and left sides
Coronal (Frontal) Plane – divides body into front and back regions
Transverse Plane – divides body into upper and lower regions
External Anatomy:
Determine the gender of your pig by looking at its posterior end under the tail. If there is a single opening, your pig is a male. If there are two openings, your pig is a female.
Gender of your pig ____________________
Gestation for the fetal pig is 112-115 days. The length of the fetal pig can give you a rough estimate of its age. Use a ruler and measure your pig from its nose to its posterior end.
11mm – 21 days
17 mm – 35 days
2.8 cm – 49 days
4 cm – 56 days
22 cm – 100 days
30 cm – birth
How old do you estimate your pig is? __________ days
Observe the toes of the pig. How many toes are on the feet? ___________________
Do they have an odd or even number of toes? _________________
Look on the underside of the chin. You should see a small bump that looks like a mole, and it should have hair growing from it. This is called the hairy papilla, and it is where you will begin your incisions.
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Incisions:
1.
Using a scalpel, cut the cheeks from the opening of the mouth dorsally toward the ears. This should allow the mouth to open fully, exposing the back of the throat.
2.
Using a scalpel, cut in a straight line from the hairy papilla to the umbilical cord of the pig.
3.
At the umbilical cord, cut around it on either side.
4.
From the umbilical cord, make diagonal incisions that extend to the hind legs. This should allow a flap of abdominal tissue to fold downwards.
5.
Make two lateral incisions superior to the hind legs, and two more inferior to the ribcage. This allows the abdominal wall to fold outward, exposing the abdominal cavity.
6.
Using scissors or bone shears, cut through the central portion of the ribcage.
7.
Make two lateral incisions inferior to the forelimbs. This allows the ribs to fold outward, exposing the thoracic cavity.
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For the Lab Practical, you should know the locations in the pig’s body of all the following organs, and their functions. Use the checklist to keep track of all the organs and body parts you need to see.
Located medially in the center of the chest cavity is the heart. It has 4 chambers and pumps blood to the pig’s body.
Located laterally on either side of the chest cavity are the lungs. Each lung has two lobes, and has a spongy texture.
They perform gas exchange for the pig.
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 neck anterior to the heart. Its anterior opening is covered by the epiglottis, which prevents food from entering the trachea. You will probably have to cut into the mouth to see the epiglottis.
At the anterior end 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.
The diaphragm is the muscle dividing the thoracic and abdominal cavity and is the thin band of tissue located inferior to the ribcage. The diaphragm aids in breathing, and when it spasms, it causes hiccups.
The liver is the largest organ in the body. It is dark red, has 3 lobes and is on the right side of the pig just inferior to the diaphragm. It cleans the blood of toxins and makes bile for digestion.
The gall bladder is a greenish balloon-shaped organ located inferior to 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.
The stomach is a pouch-shaped light-colored organ that rests just caudal to the diaphragm and is on the pig's left side.
The stomach is responsible for churning and breaking down food. At the top of the stomach, you'll find the esophagus, which connects the mouth and stomach. You can also see the beginning of the esophagus behind the trachea in the neck region.
At each end of the stomach are valves that regulate food entering and leaving the stomach. At the anterior end near the esophagus is the cardiac sphincter valve, and at the posterior end near the duodenum (small intestine) is the pyloric
sphincter valve. If you are up for it, view the inside of the stomach by slicing it open lengthwise.
The stomach leads to the small intestine, which is composed of the duodenum (straight portion just posterior to the stomach) and the ileum (curly part). In the small intestine, further digestion occurs and nutrients are absorbed through the arteries in the mesentery.
The ileum of the small intestine is held together by mesentery, which is a thin layer of tissue. Gently lift the small intestine to see the mesentery and the mesenteric blood vessels.
The pancreas is a bumpy organ located along the inferior side of the stomach. Gently lift the stomach to look underneath for the pancreas. A pancreatic duct leads to the duodenum. The pancreas makes insulin for uptake of sugars from the blood, and digestive enzymes for food breakdown.
The spleen is a flattened organ that lies along the stomach and toward the extreme left side of the pig. It is shaped like a tongue. The spleen stores and cleans blood and is not part of the digestive system.
At the posterior end of the ileum (small intestine), 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. It is similar to the appendix in humans.
The large intestine, or colon, is packed into a tightly coiled ball that lies near the small intestine, and can be traced to the caudal end of the digestive system. The large intestine reabsorbs water from the digested food, and any undigested food is excreted.
The rectum lies on the dorsal side of the abdominal cavity of the pig and stores solid waste before it is excreted. It is the last portion of the large intestine. The rectum opens to the outside of the pig, through a sphincter muscle called the anus.
Lying laterally on the dorsal side of abdominal cavity near the spine are the kidneys. These bean-shaped organs remove waste and harmful substances from the blood, and these substances are excreted as urine.

The tubes leading caudally from the kidneys that carry urine are the ureters. The ureters carry urine to the urinary
bladder, which is located near the umbilical cord. The urethra passes urine outside the pig. In the female pig, the urethra opens ventral to the anus.
In the female, the uterus is a curled structure ventral to the rectum but dorsal to the urinary bladder, and extends laterally to both sides. This is called a bilateral or “horned” uterus, and it allows gestation of multiple young at a time. At both ends are small bean-shaped structures, which are the ovaries, which store eggs.
In the male, the penis forms part of the umbilical cord structure. Look for a single opening for the urethra near the tip of the umbilical structures. The testes form a large bulge at the posterior end of the pig, inferior to the anus.