Dissection Instructions

1. Place the frog in the dissecting pan ventral side up.

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2. Use scissors to lift the abdominal muscles away from the body cavity.Cut along the midline of the body to the forelimbs.3.Make transverse (horizontal) cuts near the arms and legs.4.Life the flaps of the body wall and pin back.

*Ifyour specimen is a female, the body may be filled with eggs. You may need to remove these eggs to view the organs.

Locateeach of the organs below. Check the box to indicate that youfound the organs.


1. FatBodies --Spaghetti shaped structures that have a bright orange oryellow color, if you have a particularly fat frog, these fat bodies mayneed to be removed to see the other structures. Usually they are locatedjust on the inside of the abdominal wall.

2. Peritoneum ­ A spider-web like membrane that covers many of the organs, most easily seen covering the heart.

3. Liver--Thelargest structure of the the body cavity. This brown colored organ iscomposed of three lobes. The right lobe, the leftanterior lobe, and the left posterior lobe. The live secretes a digestive juice calledbile which is needed for the proper digestion of fats.

4. Heart - at the top of the liver, the heart is a triangular structure. The leftand right atrium can be found at the top of the heart. A single ventricle located at the bottom of the heart. The large vessel extending out fromthe heart is the conus arteriosis.

5. Lungs - Locate the two spongy lungs by looking behind the heart and liver..

6. Gall Bladder --Lift the lobes of the liver,there will be a small green sac under the liver. This is the gall bladder,which stores bile. (hint: it kind of looks like a booger)

7. Stomach--Curving from underneath the liveris the stomach. The stomach is the first major site of chemical digestion.Frogs swallow their meals whole. Follow the stomach to where it turnsinto the small intestine. The pyloric sphincter valve regulatesthe exit of digested food from the stomach to the small intestine.

8. Pancreas - This structure is located on the inside curve of the stomach. It it a gland that often falls apart during the preserving process so it many not be visible on your frog.

9. SmallIntestine--Leading from the stomach. The first straight portionof the small intestine is called the duodenum, the curled portionis the ileum. The ileum is held together by a membrane calledthe mesentery. Note the blood vessels running through the mesentery,they will carry absorbed nutrients away from the intestine. Absorptionof digested nutrients occurs in the small intestine.

10. LargeIntestine--As you follow the small intestine down, it willwiden into the large intestine. The large intestine leads to the cloaca, which is the last stop before solid wastes,sperm, eggs, and urine exit the frog"s body. (The word "cloaca" meanssewer.) The opening to the outside of the doy is the anus.

11. Spleen--Return to the folds of the mesentery, this dark redspherical object serves as a holding area for blood.

12. Esophagus--Return to the stomach and followit upward, where it gets smaller is the beginning of the esophagus.The esophagus is the tube that leads from the frogs mouth to the stomach.Open the frogs mouth and find the esophagus, poke your probe into itand see where it leads.


Removal of theStomach: Cut the stomach out of the frog and open it up. You may find whatremains of the frog"s last meal in there. Look at the texture of the stomachon the inside.

Whatdid you find in the stomach?

Measuring the Smallintestine: Remove the small intestine from the body cavity and carefullyseparate the mesentery from it. Stretch the small intestine out andmeasure it. Now measure your frog. Record the measurements below in centimeters. Frog length:_______ cm Intestine length ________ cm

Urogenital System

The frog"s reproductiveand excretory system is combined into one system called the urogenital system.You will need to know the structures for both the male and female frog

Kidneys - flattened bean shaped organs located atthe lower back of the frog, near the spine. They are often a dark color. Thekidneys filter wastes from the blood. Often the top of the kidneys have yellowish stringy fat bodies attached.

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Testes - in male frogs, these organs are located atthe top of the kidneys, they are pale colored and roundish. Oviducts - females do not have testes, though youmay see a curly structure around the outside of the kidney, these arethe oviducts. Oviducts are where eggs are produced. Males can havestructures that look similar, but serve no actual purpose. In males, theyare called vestigial oviducts.

Bladder - An empty sac located at the lowest partof the body cavity. The bladder stores urine.

Cloaca - mentioned again as part of the urogenitalsystem - urine, sperm and eggs exit here.

Label the parts of the urogenital system.

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Post Lab Questions

1. The membrane holds the coils of the small intestine together: _________________________2.This organ is found under the liver, it stores bile: ___________________________3. Name the 3 lobes of the liver: _____________________, ____________________, ____________________4. The organ that is the first major site of chemical digestion: _______________________5. Eggs, sperm, urine and wastes all empty into this structure: __________________________6. The small intestine leads to the: _______________________________7. The esophagus leads to the: ______________________________8. Yellowish structures that serve as an energy reserve: _________________________9. The first part of the small intestine(straight part): ____________________________10. After food passes through the stomach it enters the: _________________________11. A spiderweb like membrane that covers the organs: ___________________________12. Regulates the exit of partially digested food from the stomach: _____________________13. The digestive system ends at the opening called the:________________________14. Organ found within the mesentery that stores blood: __________________________15. The largest organ in the body cavity: __________________________

Label the Diagram

A. __________________________________B. __________________________________C. __________________________________D. __________________________________E. __________________________________F. __________________________________G. __________________________________H. __________________________________I. __________________________________J. __________________________________K. __________________________________L. __________________________________M. __________________________________N. __________________________________P. __________________________________

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This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Credits: Title Frog at Top - http://www.clker.com/clipart-coolred-eyed-frog.htmlFrog Urogenital Systems were modifed from http://biodidac.bio.uottawa.ca/ Frog Labeling modifed from an unknown scource, letters were added as were missing organs

This is part of a dissection series that includes: Frog External Anatomy | Frog Dissection | Frog Brain and LegPictures of Dissected from with labels are available at Frog Dissection Gallery