Fetal Pig Anatomy Dissection

Sorry guys but you will not get the chance to examine the internal organs of a real human body. Instead, human anatomy can be studied by examining the systems of a pig, an animal similar to a human. The pigs we are dissecting are called fetal pigs. Fetal pigs have not been born. Evidence that they are fetal can be seen by examining the abdominal ventral area for the attached umbilical cord.

In this investigation, you will: a. Properly dissect a fetal pig’s digestive, respiratory and circulatory systems to examine and identify its major organs and structures b. Label diagrams of a pig’s systems

Materials: Scissors Dissecting probe Lab aprons Scalpel Dissecting pins Metric ruler Dissecting tray Goggles String

Procedures: External Anatomy  Determine the sex of your pig. Both sexes have a double row of nipples along the ventral body surface therefore; these structures will not help you determine sex. A male pig has a small genital opening on the ventral surface below the area where the umbilical cord enters. A female pig has a vaginal opening next to the anus. These two openings are found under the pig’s tail. A male pig has only the anal opening. If your pig is female, you should also note that urogenital papilla is present near the genital opening. What is the sex of your pig?______

 With scissors, make a 3-cm incision in each corner of the pig's mouth. Your incision should extend through the jaw. Spread the jaws open and examine the tongue. Be careful of the sharp canine teeth in the mouth! Observe the ridged palate on the roof of the mouth. The front part of the palate is the hard palate, while the posterior part is the soft palate. Examine the tongue and note tiny projections called sensory papillae. Next, locate the teeth of the pig. Canine teeth are longer for tearing food, while incisors are shorter and used for biting. Pigs are omnivores, eating plants and animals.  Locate the epiglottis, a cone-shaped structure at the back of the mouth. Above the epiglottis, find the round opening of the nasopharynx. This cavity carries air from the nostrils to the trachea, a large tube in the thoracic which supplies air to the lungs.  Under the epiglottis is a slit. This slit is the glottis which is the opening to the trachea. Above the glottis, find the opening to the esophagus. This appears as a horizontal slit.  The openings at the most anterior end of the snout are the nares. As in the frog, these structures allow air to pass in and out of the nasal chamber.  Label the drawing of the inside of the pig's mouth. Label the following on the diagram below: Tongue Hard palate Papillae (Use twice) Epiglottis Soft palate Canines Esophagus Glottis Nasopharynx Nares

 Clean up your materials and work area. Put the pig in a zip-lock plastic bag. Label your bag with your names. Clean and return your lab equipment and pig, wash your table and then thoroughly wash your hands with soap. Internal Anatomy  Be sure to wear your lab apron and eye cover. Obtain your dissecting equipment and pig. Place the fetal pig ventral side up in the dissecting tray. Tie a string securely around a front limb. Run the string under the tray, pull it tight, and tie it to the other front limb. Repeat this procedure with the hind limbs to hold the legs apart so you can examine internal structures.  Study the diagram below. The dashed lines show the lines of the incisions that you will make.

 With scissors, make the incisions. Be sure to keep the tips of your scissors pointed upward because a deep cut will destroy the organs below. Also, remember to cut away from yourself.  After you have made your incisions through the body wall, you will see the peritoneum, a thin layer of tissue that lines the body cavity. Cut through the peritoneum along the incision lines.  Spread the flaps of the body wall apart. Cut the umbilical vein which extends through the liver.  Once the vein is cut, carefully pull the flap of skin, including the end of the umbilical cord between the hind legs. You are now able to see the organs of the abdominal cavity.  At this point, you should place your pig in the sink and wash out the body. Using paper towels, dab the water out of the body cavity.

Digestive System  The liver is a large, lobed, brown organ occupying the top portion of the abdominal cavity. A coiled mass of thick, tube-like tissue is the large intestine. The small intestine is a coiled mass of thin tube- like tissue.  A coiled mass of thick, tube-like tissue is the large intestine. The mass of coiled thin, tube-like tissue is the small intestine held together by mesentery. Above the pig’s liver is a think muscle called the diaphragm. It separates the abdominal cavity from the thoracic (chest) cavity.  Pull the umbilical cord down between the hind legs of your pig. The umbilical cord just after entering the pig’s body divides into two blood vessels called the umbilical blood vessels. They lie on each side of a flat structure called the urinary bladder.  A saclike structure attached to the underside of the liver is the gall bladder. It is usually green and is partly embedded in the liver. Leading from the gall bladder and extending along the underside of the liver is a tube called the bile duct. Directly below the liver on the right (pig’s left side) is a large pouch. This is the stomach. Leading into the top portion of the stomach is the esophagus. It appears to be rather short because it passes upward behind the liver. Attached along the right edge of the stomach is a round, reddish organ, the spleen. The spleen looks more like a flap lying near the stomach. A rough or coarse organ lying directly below and extending along the underside of the stomach is the pancreas. Extending from the stomach toward the left side (pig’s right) is a tube which is the beginning of the small intestine. This part is the duodenum. Both the pancreas and the gall bladder empty digestive chemicals into this structure. The bile duct which leads from the gall bladder to the duodenum should be visible. The duct leading from the pancreas is small and difficult to locate. At the junction between the small and large intestines is a small, fingerlike projection. This structure is the caecum (our appendix).  Push the intestines as far to your left as possible. Also, pull the urinary bladder and umbilical cord down. A tube leading from the large intestine out of the abdominal cavity towards the pig’s tail is the rectum. The opening of the rectum to the outside on the animal’s body is the anus.  Identify and label the organs of the digestive system listed below: Liver Stomach Rectum Large intestine Duodenum Esophagus Small intestine Spleen Umbilical blood vessel Caecum Pancreas Umbilical cord Gall bladder Bile duct Anus

Identify the organ (or structure) ______Produces bile and detoxifies the blood. ______The “dead end” at the junction of the small and large intestines. ______Separates the thoracic and abdominal cavity; aids breathing. ______Membrane that holds the coils of the small intestine in place. ______Liquefies foods using acids and begins protein digestion.. ______The holding chamber for feces before it exits at the anus. ______Bumpy structure under the stomach that produces insulin. ______Location where most of the chemical digestion and absorption takes place. ______Part of the immune system that removes old red blood cells. ______Absorbs water from the remaining indigestible food matter.

Respiratory System  Extend the cut in your pig’s chest cavity made during the examination of the digestive system. Continue cutting in a straight line along the middle of the chest up to the chin.  Locate the trachea, a long tube composed of ring-like sections extending along the middle of the chest cavity. Lying ventral to the trachea or windpipe, locate the pinkish-brown, V-shaped structure called the thyroid gland. What is the purpose for the cartilage rings on the trachea? ______ Push aside muscle attached to the top portion of the trachea. A slight bulge in the trachea is the larynx or voice box. Cut lengthwise into the larynx with scissors to expose the vocal cords.  Locate the left and right lungs. These organs are composed of soft tissue and have many lobes which occupy most of the chest cavity.  Remove any tissue covering the lower portion of the trachea. The trachea branches into each lung. These branches are the left and the right bronchi.  Between the chest and abdominal cavity is a very thin sheet-like muscle. The muscle, called the diaphragm separates the thoracic cavity from the abdominal cavity and it also aids in inhaling and exhaling.  Label the structures of the respiratory system below: Trachea Diaphragm Left bronchus Larynx Left lung Right bronchus Vocal cords Right lung

Right Side Left side

 Where the bronchi enter the lungs, the bronchi again branch off into bronchial tubes. These branches continue to branch off until they are very small and do not contain cartilage rings. They end as many small air sacs called alveoli. Alveoli are very thin walled and are surrounded by capillaries of the lungs. It is in the alveoli where gas exchange occurs between blood and air.

Circulatory System  Locate the heart. It is covered by a thin tissue called the pericardium. Remove this membrane to study the heart. The coronary blood vessels are the web-like blood vessels on the surface of the heart to supply the heart tissue with blood. What would happen if one of the coronary blood vessels becomes blocked? ______ Pigs, like all mammals, have four-chambered hearts. The right side of the heart pumps blood to the lungs, while the left side of the heart pumps blood to all other parts of the body. Locate the right and left sides of the heart. Separating the two sides of the heart is a muscular tissue called the septum.  Each side of the heart has an upper and a lower chamber. Upper chambers are called atria and receive blood, while lower chambers are called ventricles and pump blood out of the heart. Locate the right and left atria and ventricle. What is the advantage of a 4 chambered heart? ______ Notice that the surface of the heart is covered with blood vessels. These are part of the coronary circulation, a set of arteries and veins whose only job is to nourish the heart tissue. Blockage in these vessels causes heart attacks.  Anterior to the heart, locate another large vein that enters the right atrium. This vein, the superior vena cava, brings blood to the right atrium from the anterior part of the body.  Now lift the heart to view its dorsal surface. Observe the inferior vena cava that carries blood from the posterior part of the body and empties it into the right atrium.  Find the pulmonary artery which leaves the right ventricle. After birth, this vessel carries blood to the lungs. However, in a fetus, a shunt called the ductus arteriosus allows fetal blood to bypass the lungs and go directly to the aorta, the largest artery of the body. Locate the pulmonary veins that enter the left atrium. After birth, these vessels carry oxygenated blood from the lungs to the heart.  Identify the aorta, a large artery that transports blood from the left ventricle. Many arteries that carry blood throughout the body branch off of the  Remove the heart by severing the blood vessels attached to it.  Hold the dorsal and ventral surfaces of the heart with your thumb and forefinger and rest the ventricles on your dissecting tray. With a scalpel, cut the heart into dorsal and ventral halves. Caution: The scalpel is very sharp. Use it carefully and always cut away from yourself.  Remove any material inside the heart and expose the walls of the atria and the ventricles. Compare the walls of the atria to the walls of the ventricles.______ Study the internal features of these chambers and note where vessels leave or enter each chamber. Locate the tricuspid valve between the right atrium and ventricle and the mitral valve between the left atrium and ventricle. Between the right ventricle and the pulmonary artery is the pulmonary valve and between the left ventricle and the aorta is the aortic valve. These structures prevent blood from flowing backward in the heart. What would happen if the heart did not have valves?______

 Label the diagram below of the mammalian heart: Inferior vena cava Right AV Valve Left atrium Superior vena cava Left AV Valve Right ventricle Aorta Pulmonary valve Left ventricle Pulmonary artery Aortic valve Septum Pulmonary vein Right atrium Left side Right side Urogenital System  Locate the kidneys and the tubes leading from the kidneys that carry urine called the ureters. The ureters carry urine to the urinary bladder, located between the umbilical vessels. Lift the bladder to locate the urethra, the tube that carries urine out of the body. Note the vessels that attach to the kidney , these are the renal vessels  Male Find the scrotal sacs at the posterior end of the pig (between the legs), testes are located in each sac. From each testis, find the coiled epididymis. Sperm cells produced in the testes pass through the epididymis and into a tube called the vas deferens (in humans, a vasectomy involves cutting this tube). 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.  Female In the female pig, locate two bean shaped ovaries located just below the kidneys and connected to the curly oviducts. 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.  On the diagrams below of the female and male urogenital systems, label the following: Ovary Ureter Urinary bladder Kidney Uterus Vas deferens Oviducts Urethra Testes

Female Male