STUDENT LABORATORY PACKET

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1 L10 Frog Dissection_Internal Page 1 of 10 STUDENT LABORATORY PACKET LAB # 10 Bull Frog: Internal Examination Student s Name Edited version from Prentice Hall Lab. Manual Lab Instructor Date Points Objectives: 1. To observe the internal anatomy of the frog 2. To compare the systems in a frog to a human Pre Lab (Do Before Coming to Lab Bring 2 diagrams showing the internal anatomy of a frog. Describe each HUMAN system (you will later compare the humans systems to the frog after the dissection). 1. Human Circulatory System: a) Heart: o Total number of chambers o Number of atria o Number of ventricles b) Describe the path that blood flows during pulmonary circulation starting with the right atrium and ending with the left ventricle. Include whether or not oxygenated or deoxygenated blood is in each structure. 2. Human Digestive System: a) What type of diet do humans have? What type of heterotroph are humans? b) List the order of the structures food passes through during digestion: c) List the accessory organs and their functions: d) How many lobes does the human liver have? 3. Human Urinary System: a) What materials exit the human urinary system? 4. Human Respiratory System: a) List the type of respiratory surface found in humans: b) What is the mechanism of gas exchange? (How is oxygen and carbon dioxide exchanged?) c) How are lungs adaptations for gas exchange on land? 5. Reproduction and Development: NOT related to humans. Define each: a) Compare internal and external fertilization. b) Compare internal and external development.

2 L10 Frog Dissection_Internal Page 2 of Laboratory Exercise Materials: a preserved single injected frog, dissecting tray, scissors, hand lens, latex gloves, probes, forceps, dissecting noodles, plastic ruler, dissecting microscope. Procedure: Note: All students should wear gloves. If you have an allergy to latex, wear plastic gloves. Please do not mutilate your specimen. It was once living. 1. Get your labeled frog from your instructor. Be careful handling them since you cut their mouth. Take the usual lab pre-cautions: tie back long hair, wear gloves, and wear an old T shirt/smock. Suggestion have one student be the reader. He/she should read the procedure aloud. 2. Place the frog on the dissecting tray, ventral side up, anterior end pointing away from you. Refer to the diagram on the right to see where the incisions should be made. Cut through the skin only along line a, all the way to the chin. Then cut the skin along incision lines b, c, d, and e. Pin the loose skin to the dissecting tray to expose the muscles of the frog. Note the many fine blood vessels on the underside of the skin. a. Why does the skin contain so many fine blood vessels? (Hint: Think of what you learned about the skin in last week s lab). 3. Using scissors, cut the muscles along incision line a up to the forelimbs (not all the way to the jawbone). Make a shallow cut through the muscle only so that you do not damage the organs underneath. When cutting near the forelimbs, you have to cut through the bone of the rib cage. The heart is directly beneath the rib cage, so work carefully. 4. Continue cutting along incision line a to the jawbone, cutting through muscle only do not destroy the floor of the mouth. Then make cuts through the muscle along incision lines b, c, d, and e. Take hold of the two forelimbs and stretch them widely apart so that the chest cavity opens. Place a large dissecting pin in each limb at an angle of about 45 degrees. Pin back the muscles, exposing as much of the internal organs as possible. 5. If the frog is a female, two large masses of black eggs may be hiding the internal organs. The eggs are in a thin ovary tissue so that you can see the separate eggs. After examining them, remove the egg masses by lifting them carefully and cutting the two ovaries free from the body. a. Is your frog a female or a male? Is this the same gender you determined from the external examination? 6. Using the diagrams at the back of the lab and the ones you brought, briefly see which organs you can identify. As you go through the procedure, you will remove the organs one at a time. After removal, they should be placed in the appropriate box on the chart so your teacher can check your group s work. 7. The frog stores extra food at times of heavy feeding (in the summer) in the form of fat bodies. When food is scarce, or during hibernation, the fat bodies provide energy for life processes. They are necessary to provide

3 L10 Frog Dissection_Internal Page 3 of 10 energy for the production of eggs and sperm in the spring breeding season. Observe the yellow, finger-shaped fat bodies. In the male frog, the fat bodies will be more visible when you do the urinary tract examination. Remove them and place them in the chart. a. How long are the fat bodies?. 8. Locate the heart. It is in a triangular pericardial sac (a very thin, transparent layer of skin surrounding the heart). Open the pericardial sac. Using a scalpel, remove the heart and place it in the dissecting tray. Slice the heart open sideways (make a coronal cut, which is how you dissected the sheep heart) to see the chambers. If you are unable to observe the chambers, view a different group s dissected heart or the one at the teacher s desk under a dissecting microscope. a. How many atria are there? Ventricles? b. How can you distinguish between the two types of chambers? c. Draw a picture of the open heart, labeling the chambers: 9. Place the heart back into the chest cavity of the frog. Fold the skin of the frog so it covers and protects the organs and secure it with a rubber band with your group s number on it. Place it in the bag at the teacher s desk Laboratory Activity Week The liver is the largest organ in the frog body. It is also the largest gland in the human body. a. How many lobes does this liver have? 11. Attached to the underside of the liver is the gallbladder. A bile duct connects the gallbladder to the intestine. It is a green-yellow sac attached to the liver. Examine the connection between the gall bladder and the liver. a. What is stored in the gall bladder? What is its role in digestion? 12. Remove the liver and gall bladder and place them on the chart. 13. The stomach is a C-shaped bag under the liver. It is on the frog s right side. The anterior end of the stomach is connected to the esophagus; the posterior end is connected to the small intestine, a small-coiled tube. 14. Find the pancreas, a feather-shaped organ located just dorsal to the stomach and attached to the bile duct by a small tube, the pancreatic duct. Remove the pancreas and place it on the chart. 15. Trace the small intestine toward the posterior of the frog using the blunt probe. Be careful not to tear any tissue. The small intestine joins the shorter large intestine. It leads deep into the posterior abdominal cavity. Just anterior to the anus, between the hind limbs, the large intestine is joined by the urinary bladder, a twolobed, thin-walled sac that may be lying on top of to one side of the large intestine. Locate the cloaca (externally), an orifice (opening) where the legs meet. Feces, urine, eggs and sperm all leave the through this orifice where the urinary, digestive and reproductive systems converge.

4 L10 Frog Dissection_Internal Page 4 of Remove the alimentary canal (digestive system) from the lower esophagus (above the stomach) to the anus and place it on the chart. Note the relative size of the stomach and the length of the small intestine. The small intestine is twisted into a helical form by the mesentery (a thin, fan-shaped membrane). If you carefully loosen/cut the membrane, you will notice how long the small intestine is. In the adult human, it is about 24 feet long. There should be a small spherical, dark red spleen attached to the mesentery between the stomach and the large intestine. a. Measure the length of the small intestine and large intestine. b. What are the functions of the small intestine and large intestine? 17. Have your teacher check the group organ chart. 18. At the anterior end of the abdominal cavity, find the two dark-red lungs. They appear deflated, long and thin or as inflated, long oval balloons. Note that the lungs are connected anteriorly with the larynx and glottis. 19. Place the alimentary canal back on the dissecting tray. Cut the stomach from the alimentary canal and cut it open using the scalpel. Examine its contents under the dissecting microscope. a. Describe the contents of the stomach. 20. If more time is remaining, open the small and large intestine in the dissecting tray and examine them under the dissecting microscope Analysis: Compare the frog and human systems. Refer back to the pre-lab and lab activity, if necessary. 1. Circulatory System: a. Compare the total number of chambers, the number of atria and the number of ventricles in the frog and human heart. b. Compare the difference in pulmonary circulation in frogs and humans. 2. Digestive System: a. Compare the diets of humans and frogs. What type of heterotroph is each? b. Are the digestive organs food passes through in the frog and human the same? Explain. c. Do frogs and humans have the same accessory organs? Which ones do they have in common? d. How many lobes are in the frog liver? In the human liver?

5 L10 Frog Dissection_Internal Page 5 of Urinary System: a. What materials exit the human urinary system? How is this different than the materials that exit through the cloaca of the frog? 4. Respiratory System: a. What types of respiratory surfaces are found in a frog? In a human? b. How does gas exchange differ between humans and frogs? How is it similar? c. How are the types of respiratory surfaces found in humans and frogs related to each organism s habitat? 5. Reproduction and Development: a. What type of fertilization (internal or external) do frogs have? Humans? b. What type of development (internal or external) do frogs have? Humans? Copy your lab onto the Student Answer Packet. Only the student answer packet will be collected and graded.

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8 L10 Frog Dissection_Internal Page 8 of 10 Student Answer Packet LAB # 10 Bull Frog: Internal Examination Student s Full Name Lab Instructor Date Period FINAL GRADE Pre-Lab Completed as homework: Max. value 5pts. pt. Procedure/Observations: Max. value 15 pts. pts. The numbers of the questions correspond to the numbers in the procedure of the lab: 2. Why does the skin contain so many fine blood vessels? (Hint: Think of what you learned about the skin in last week s lab). 5. Is your frog a female or a male? Is this the same gender you determined from the external examination? 7. How long are the fat bodies?. 8. a. How many atria are there? Ventricles? b. How can you distinguish between the two types of chambers? a. Draw a picture of the open heart, labeling the chambers: Laboratory Activity Week How many lobes does this liver have?

9 L10 Frog Dissection_Internal Page 9 of What is stored in the gall bladder? What is its role in digestion? 16. a. Measure the length of the small intestine and large intestine. b. What are the functions of the small intestine and large intestine? 19. Describe the contents of the stomach. Analysis: Max. value 25 pts. pts. 1. Circulatory System: a. Compare the total number of chambers, the number of atria and the number of ventricles in the frog and human heart. b. Compare the difference in pulmonary circulation in frogs and humans. 2. Digestive System: a. Compare the diets of humans and frogs. What type of heterotroph is each? b. Are the digestive organs food passes through in the frog and human the same? Explain. c. Do frogs and humans have the same accessory organs? Which ones do they have in common? d. How many lobes are in the frog liver? In the human liver?

10 L10 Frog Dissection_Internal Page 10 of Urinary System: a. What materials exit the human urinary system? How is this different than the materials that exit through the cloaca of the frog? 4. Respiratory System: a. What types of respiratory surfaces are found in a frog? In a human? b. How does gas exchange differ between humans and frogs? How is it similar? c. How are the types of respiratory surfaces found in humans and frogs adaptations to each organism s habitat? 5. Reproduction and Development: a. What type of fertilization (internal or external) do frogs have? Humans? b. What type of development (internal or external) do frogs have? Humans?