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Pig Dissection Introduction The fetal pig, Sus scrofa, belongs to the phylum Chordata, Class mammaila, Order Artiodactyla, genus Sus, and species scrofa. The fetal pig is an excellent animal for dissection purposes due to its resemblance to a human. Teamwork A dissection is like an operation and requires teamwork. Your team will consist of: 1. Surgeon- person who physically makes incisions with the scalpel and forceps. 2. Assistant surgeon- assists the surgeon. 3. Reader- Reads instructions and directs the surgeon. 4. Recorder- Draw and label during the dissection. Materials A large dissection cutting board String Surgical scissors with one blunt tip Scalpel Dull probes T- Pins for holding down the skin flaps Forceps Ruler Care for Your Pig At all times during the dissection it is essential that you show respect for your animal. It is also important that your specimen is sprayed with Bioshield before placing it back in the plastic bag for storage, this will prevent the tissue from drying out or becoming moldy. Dissection skills Dissection is a learned skill. Some general rules to remember are: do not make deep cuts with scissors or scalpels; you may inadvertently damage underlying tissue. Know the anatomical terms such as caudal, cranial, dorsal, ventral, medial, and distal so that you can follow the directions as you study your organism. How to Begin: Day 1 Draining the Organism 1. The “surgeon” and “assistant surgeon” need to put on gloves. Meanwhile, the “recorder” needs to have your storage bag labeled with your names and period. 2. Open the bagover the sink, and carefully allow fluids to drain into the sink. Holding the pig with two gloved hands, rinse pigs thoroughly under running water. Place pig onto dissecting board. External investigation 1. Place pig stomach down. Make a sketch and label the major structures: Pinna-Ears, Nares-Nostrils, Eye, Anus, Urogenital opening, Mammary Papillae-nipples, Umbilical cord. a. Is your pig a female or a male? _______________________ In male fetuses, the urogenital opening is located just caudal from the umbilical cord. You should also find a scrotal sac just proximal to the umbilical cord. In females the urogenital opening is just ventral to the anus. b. What is the purpose of the umbilical cord? __________________________________. Pig Dissection Superficial Muscles 1. You will skin the front right leg, front right shoulder, right side of the chest, and the back exposing the muscles of the shoulder, leg and back. Shallowly cut around the distal end of the front right leg. Shallowly cut around the neck. Make an incision through the skin at the base of the neck, between the two ears, along the dorsal ridge to the center of the back. Make an incision from under the armpit up to the incision that you made on the back. Make an incision from the neck down to the center of the chest. Carefully remove the skin covering the front right leg, and shoulder. 2. Draw and label the Trapezius, Deltoideus, Latissimus dorsi, and Triceps long head. Internal Investigation: You will not remove organs at this time 1. Place your pig on its dorsal side. Secure your pig by tying a length of string to one limb and pass it under the cutting board and tie it to the opposite limb tautly. Repeat with the other limbs. 2. At the umbilical cord, make an incision through the body wall just deep enough to cut through the muscles. Cut around the umbilical cord. Make an incision across the chest from one armpit to the other. Make an incision across the belly just above the umbilical cord. Make a connecting incision that starts from the chin, goes across your chest incision, all the way down to your belly incision, opening up the respiratory and digestive cavity. Pull back the flaps and identify all the organs on the yellow side of the accessory “Fetal Pig Dissection Guide”. End of Day One: Make sure that your instructor sprays your specimen with Bioshield for preservation purposes. Place your pig into plastic bag and seal. Place dissecting tools, sharp end down into cleaning solution. With soap and water clean the dissection tray. Beginning of Day Two Internal Investigation: Identifying and removing internal organs Dissecting out the Respiratory System and the Heart 1. Secure your pig with the string wrapped around the cutting board as you did before. 2. Begin by identifying and removing the thymus gland. The thymus is a grayish mass that rests just ventral to the heart. The thymus is where T-Cells mature and learn to tell self from non-self. The assistant surgeon should keep removed organs organized. 3. Identify the trachea and the larynx (voice box). Also identify the thyroid gland that sits near the larynx. The thyroid gland produces triiodothyronine (T3) and thyroxine (T4), which are “steroid like” hormones that increase the metabolic rate of all the cells in the body. Follow the trachea from the oral cavity down to the lungs. The right lung has four lobes and the left lung has three. 4. The heart, covered by the pericardial sac, sits between the lungs. Remove the pericardial sac and carefully pull back the lungs so that you can identify the aorta and the vena cavas. 5. Carefully remove the trachea, snip near the throat, the lungs, and the heart. Cut through the vena cavas and the aorta to remove the heart. Do not take out the esophagus, which sits just behind the trachea. Bisect the Heart 1. With the scalpel, bisect the heart, draw and label. 2. The Heart and Respiratory system are located in the thoracic cavity. Notice how the thoracic cavity is separated from the abdominal cavity by the diaphragm. Also notice how the esophagus, aorta, and caudal vena cava pass through the diaphragm and membranes separating the thoracic and abdominal cavities. Pig Dissection Removing the Digestive System 1. Use your scissors to cut the joints on both sides of the mouth. Observe the teeth, tongue, hard palate, and soft palate. The hard palate separates the mouth form the nasal cavity. The soft palate is just caudal to the hard palate. 2. How many teeth do you observe?______ 3. Observe how the esophagus connects the throat to the stomach. You will need to cut through the membranes that hold the intestines in place. 4. Look underneath the liver to find the Gall Bladder. 5. Draw and label the connection between the pancreas (grayish in color), the bile duct, and the small intestine. This should be close to where the stomach connects to the small intestine. This portion of the small intestine is called the duodenum. 6. Remove the liver. How many lobes does it have?______ What are three functions of the liver?_______________________,___________________,&_____________________ 7. Although not part of the digestive system, the spleen will be found underneath the stomach. The spleen filters the blood to remove old red blood cells. Remove this organ now. 8. Carefully remove the entire digestive tract at this time. Be sure not to remove the kidneys. You will be removing the esophagus, the stomach, the small intestine, and the large intestine. Leave an inch or so of the rectum. Notice the cecum, small finger like projection where the small intestine and the large intestine meet. This functions to digest plant material. 9. Once removed, measure the length of the entire digestive tract. How long is it?________ 10. Is there anything in the digestive tract? Why or why not?____________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ End of Day Two: Make sure that your instructor sprays your specimen with Bioshield for preservation purposes. Place your pig into plastic bag and seal. Place removed parts in a separate smaller bag. Place dissecting tools, sharp end down into cleaning solution. With soap and water clean the dissection tray. Beginning of Day Three Urogenital System 1. Extend the incision from the caudal side of the umbilical toward the tail. Open up the urogenital system as shown in the following diagrams. Depending on the sex of your specimen, either use figure six or seven to identify the following organs. Pig Dissection 2. Draw and label the urogenital system of your pig. 3. What are the functions of: a. Kidneyb. Uretersc. Urethrad. Urinary bladdere. Ovariesf. Oviductg. Uterush. Vaginai. Scrotumj. Testes- Nervous System 1. Remove the skin and tissue from the dorsal half of the head until the skull is exposed. Start at the base of the skull, in the occipital region, and carefully chip away the bone revealing the brain. Work until the entire brain is exposed. The brain is covered by three membranes, or meninges. Very carefully remove the meninges so that you may see the folds of the cerebral cortex. Diagram what you see. Be able to recognize the cerebrum, the longitudinal fissure that separates the cerebral hemispheres, the cerebellum, and the brain stem or medulla oblongata. Clean-up Place your pig into plastic bag and seal. Place removed parts in a separate smaller bag. Place dissecting tools, sharp end down into cleaning solution. With soap and water clean the dissection tray. Day 1 Surgeon_________________ Asst. Surg._______________ Reader__________________ Recorder________________ Day 2 Surgeon_________________ Asst. Surg._______________ Reader__________________ Recorder________________ Day 3 Surgeon_________________ Asst. Surg._______________ Reader__________________ Recorder________________