Name: _________________________________ Date: ___________ Frog Dissection Procedures **Important SAFETY INFORMATION 1. Students are to wear safety goggles at ALL times 2. Long hair is to be pulled back and not hanging down 3. Scissors and scalpels will be used with the BEST of care in order to avoid injury. 4. Students are to clean laboratory area as well as hands before and after lab. Failure to follow any of the above rules will result in the immediate dismissal from the laboratory. I ______________________ understand the above statement and know the consequences if I fail to follow lab rules. Signature Date EXTERNAL DISSECTION Procedure: 1. Put on safety goggles and gloves if wanted. 2. Place a frog on a dissection tray. To determine the frog’s sex, look at the hand digits, or fingers, on its forelegs. A male frog usually has thick pads on its "thumbs," which is one external difference between the sexes, as shown in the diagram below. Male frogs are also usually smaller than female frogs. Observe several frogs to see the difference between males and females. **What is the sex of your frog? Name: _________________________________ Date: ___________ 3. Use the diagram below to locate and identify the external features of the head. Find the mouth, external nares, tympani, eyes, and nictitating membranes. **What is the function of the nictitating membrane? 4. Turn the frog on its back and pin down the legs. Cut the hinges of the mouth and open it wide. Use the diagram below to locate and identify the structures inside the mouth. Use a probe to help find each part: the vomerine teeth, the maxillary teeth, the internal nares, the tongue, the openings to the Eustachian tubes, the esophagus, the pharynx, and the slit-like glottis. **Where is the frog’s tongue attached? Why do you think that is? Name: _________________________________ Date: ___________ INTERNAL DISSECTION Procedure: 1. Put on safety goggles and gloves if wanted. 2. Retrieve a frog from the teacher and place it on a dissection tray. 3. Look for the opening to the frog’s cloaca, located between the hind legs. Use forceps to lift the skin and use scissors to cut along the center of the body from the cloaca to the lip. Turn back the skin, cut toward the side at each leg, and pin the skin flat. The diagram below shows how to make these cuts. 4. Lift and cut through the muscles and breast bone to open up the body cavity. If your frog is a female, the abdominal cavity may be filled with dark-colored eggs. If so, remove the eggs on one side so you can see the organs underlying them. **Was it difficult to cut through the muscles and breast bone? Why do you think that is? **Were there any eggs inside your frog? Was your prediction of the frog’s sex correct? Name: _________________________________ Date: ___________ 5. Use the diagram below to locate and identify the organs of the digestive system: esophagus, stomach, small intestine, large intestine, cloaca, liver, gallbladder, and pancreas. **List the path that food takes through the digestive system. **Remove the small intestine. Measure and find the length of the small intestine. ______ cm Open up the stomach. Describe what you find inside the stomach. Open the large intestine and describe what you find inside. 6. Again refer to the diagram to identify the parts of the circulatory and respiratory systems that are in the chest cavity. Find the left atrium, right atrium, and ventricle of the Name: _________________________________ Date: ___________ heart. Find an artery attached to the heart and another artery near the backbone. Find a vein near one of the shoulders. Find the two lungs. **Why are a frog’s lungs so small in comparison to its size? 7. Observe the yellow fat bodies that are attached to the kidneys. Find the ureters; the urinary bladder; the testes and sperm ducts in the male; and the ovaries, oviducts, and uteri in the female. **Fat bodies are used to help keep frogs warm. Why do you think frogs store their fat in their stomach cavity instead of under the skin like humans? 8. Dispose of your materials according to the directions from your teacher. 9. Clean up your work area and wash your hands before answering the post-lab questions. Name: _________________________________ Date: ___________ POST DISSECTION QUESTIONS 1. How were the items in the stomach and large intestine different? Why do you think that is? 2. Based on what you found in your frog’s digestive system, what do you think this type of frog might eat? 3. Frogs are amphibians. Which features of the frog’s anatomy might help them live both in water and on land? How do they help? 4. What was the largest organ that you found inside your frog? 5. How is the tongue adapted to help it catch prey? 6. What organ systems were you able to identify in your frog? Name: _________________________________ Date: ___________ 7. How is frog dissection helpful in understanding more about humans? 8. What was the most interesting/surprising thing you found during the dissection? 9. Overall, what did you think of the dissection? Why?