Mammalian Dissection: Fetal Pig Integrated Science 4 Honors

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1 Mammalian Dissection: Fetal Pig Integrated Science 4 Honors Name Per. Introduction Organisms are classified based on similarities and differences to: 1) make sense of the millions of organisms on record, and 2) predict the evolutionary relationships among them. In this laboratory, you will gather evidence on a mammal s (fetal pig s) anatomy and physiology as a basis for comparison with other vertebrates. Part A. External Anatomy Use your Integrated Science book (Chap 24 and 25) and or other available resources to label the following items on the diagram below. 1. Label the following regions: dorsal, ventral, anterior, posterior, cranial region, pectoral region, pelvic region, and caudal region. In addition, note the areas where the thoracic cavity and abdominal cavity are found. 2. Label these external structures: umbilical cord, snout (nares), eye, ear (pinna), mouth, leg, hoof, anus. Part B. Dissection Procedures Beginning of each dissection day: 1. Obtain specimen, gloves, twine/string, and dissection kit (with scissors, tweezers, probe(s), scalpel/blade). Dissection: 2. Place the specimen on its dorsal side on a dissecting tray. Use the twine to tie the pig s legs as demonstrated. Then make incisions through the body wall in the order shown in the dissection guide. Make initial incisions with scalpel/blade and longer cuts with scissors. Be careful to cut around the umbilical cord and make your cuts deep enough (use scissors) to cut just through the muscles. Pin the flaps of muscles away to expose the abdominal cavity and other internal cavities. 3. To expose the thoracic cavity make a horseshoe cut out of the ribs with the blunt-tipped dissecting scissors as shown on the figure with the dotted line. To identify gender, look for the urogenital papilla on the posterior end ventral to the anus and tail. If it is there, your pig is female. If not, it is male. Follow additional instructions for dissection in handouts or from your teacher. You can also go online to the website listed above. Part C. Observations/Data 1. Observe your dissected mammal specimen (fetal pig). You will make a series of biological drawings that will serve as your data for this laboratory activity. All biological drawings must have a title and a scale. Good biological drawings may/should also include written notes to support the drawing. Dissection manuals will be available to help you. The chart below indicates the organs you will be responsible for identifying and learning, as well as the color coding system you will use in your drawings.

2 Organ System Cardiovascular/ Circulatory Color Cavity (where primarily found) Thoracic Organs (draw and label, identify on specimen, know function) Heart, Blood Vessel (artery or vein) Respiratory Thoracic Diaphragm, Trachea, Lungs Digestive Abdominal (ventral) Stomach, Liver, Pancreas, Small Intestines, Large Intestines, Rectum, Cecum Urinary/ Excretory Abdominal (dorsal) Kidney, Ureter, Urinary Bladder Reproductive Nervous Abdominal (dorsal) Cranial Male: Testes, Urethra Female: Ovary, Oviduct, Uterus Spinal Cord, Brain (brain stem, cerebellum, cerebrum), Eyes 2. On the attached Specimen Drawing templates, color and label structures from each of the major organ systems as indicated above. You will be responsible for making (6) drawings: 1) Abdominal and Thoracic Cavities ventral view in situ (as you see it with nothing removed) 2) Heart mid-line section of extracted organ 3) Digestive System ventral view of extracted system 4) Abdominal Cavity ventral view in situ with digestive system removed 5) Brain dorsal view of extracted brain 6) Brain ventral view or mid-line section of extracted brain 3. Identify the important organs that are visible in the thoracic and abdominal cavities Complete the first required drawing from above. 4. In the thoracic cavity, carefully remove the heart, keeping as much of the blood vessels as possible attached. Identify the blood vessels and heart structures that are involved in the double-loop circulation. With your instructor s guidance, make a mid-line cut through the heart. Complete the second required drawing from above. 5. In the abdominal cavity, carefully remove the digestive tract. Do this by making a single cut above the stomach and below the large intestine/rectum. You should be able to remove the system intact. This will reveal the important organs in the dorsal layer of the abdominal cavity. Using the extracted digestive system, complete the third required drawing from above. 6. Identify the organs remaining in the dorsal layer of the abdominal cavities. Complete the fourth required drawing from above, noting the gender of your specimen. Find a team in your class with a specimen of the opposite gender and make a quick observation of the similarities and differences with your specimen. 7. Using careful technique, extract the pig s brain. Do this by first removing skin from the skull. Carefully cut through the skull from back to front along the midline. Cut around the bottom edge of the skull to remove the skull in two parts. This should expose the brain. Make a cut at the rear of the brain, where the spinal cord enters. Using your blunt probe work under the brain to break any remaining connections. Remove the brain intact 8. Identify the spinal cord, cerebellum, cerebrum and brain stem. Complete your fifth drawing from a dorsal view identifying as many structures as possible. 9. For your final drawing you will have an option. Complete your sixth drawing from either a ventral view or by cutting the brain in half and presenting a mid-line view. Label as many structures as possible. 10. Use all available resources (textbook, worksheets, dissection manuals) to complete the structure/function worksheet. Part D. Clean up At the end of each dissecting day, return you specimen to a labeled plastic bag, saving all of the dissecting fluid. Clean and dry lab tray, tools, and work area. This will be checked by your teacher. Clean out the sink at your lab station. Wash your hands!

3 Analysis and Discussion 1. Complete the table below, considering adaptations observed during the laboratory activity. Adaptation Function Evolutionary Importance and/or Evidence of Specimen s Metabolic Rate. Example: Fat and Fur 1. Body Insulation Thick layers of fat and hair help retain body heat. This is an important adaptation for endothermic organisms because it helps to prevent heat loss Answer the following using complete sentences: Metabolism (endothermy or ectothermy) is a physiological characteristic and is impossible to directly observe with a dead specimen. Nevertheless, indirect evidence is present. Discuss any structural features that you have observed that could provide indirect evidence of your specimen s metabolic rate. Consider, in particular, how the structures you discuss may be different from structures in organisms that use a different metabolic system.

4 Specimen Drawings Thoracic and Abdominal Cavities: Ventral View in situ

5 Heart (extracted): Mid-line section Digestive System (extracted): Ventral View

6 Ventral Abdomen View of Fetal Pig (digestive removed) Abdominal Cavity- Ventral view in situ with digestive organs removed Sex:

7 Brain (extracted): Dorsal View Brain (extracted): Ventral View or Mid-Line Section