1. Place the frog in the dissecting pan ventral side up.
2. Use scissors to life the abdominal muscles away from the body
cavity. Cut along the midline of the body from the pelvic to
the pectoral girdle.
3. Make transverse (horizontal) cuts near the arms and legs.
4. Life the flaps of the body wall and pin back.
*If your specimen is a female, the body may be filled with eggs and an
enlarged ovary. You may need to remove these eggs to view the organs.
Locate each of the organs below. Check the box to indicate
that you found the organs.
|Fat Bodies --Spaghetti shaped structures that have a bright orange or yellow color, if you
have a particularly fat frog, these fat bodies may need to be removed to see the other structures. Usually they are
located just on the inside of the abdominal wall.
|Peritoneum A spider web like membrane that covers many of the organs, you may have
to carefully pick it off to get a clear view
|Liver--The largest structure of the the body cavity. This brown colored organ is composed
of three parts, or lobes. The right lobe, the left anterior lobe, and the left posterior lobe.
The liver is not primarily an organ of digestion, it does secrete a digestive juice called bile. Bile is needed for
the proper digestion of fats.
|Heart - at the top of the liver, the heart is a triangular structure. The left and 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 from the heart is the conus arteriosis.
|Lungs - Locate the lungs by looking underneath and behind the heart and liver. They are
two spongy organs.
|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)
|Stomach--Curving from underneath the liver is the stomach.
The stomach is the first major site of chemical digestion. Frogs swallow their meals whole. Follow the stomach
to where it turns into the small intestine. The pyloric sphincter valve regulates the exit of digested food from
the stomach to the small intestine.
|Small Intestine--Leading from the stomach. The
first straight portion of the small intestine is called the duodenum, the curled portion is the ileum.
The ileum is held together by a membrane called the mesentery. Note the blood vessels running through the mesentery,
they will carry absorbed nutrients away from the intestine. Absorption of digested nutrients occurs in the small intestine.
|Large Intestine--As you follow the small intestine
down, it will widen into the large intestine. The large intestine is also known as the cloaca in the frog.
The cloaca is the last stop before wastes, sperm, or urine exit the frog's body. (The word "cloaca" means sewer)
|Spleen--Return to the
folds of the mesentery, this dark red spherical object serves as a holding area for blood.
Esophagus--Return to the stomach and follow
it 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 it and see where it leads.
STOP! If you have not located each of the organs above, do not continue
on to the next sections!
Removal of the Stomach: Cut the stomach out of the frog
and open it up. You may find what remains of the frog's last meal in there. Look at the texture of the stomach
on the inside.
What did you find in the stomach?
Measuring the Small intestine: Remove the small intestine
from the body cavity and carefully separate the mesentery from it. Stretch the small intestine out and measure
it. Now measure your frog. Record the measurements below in centimeters.
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 large intestine leads
to the __________________
14. Organ found within the mesentery
that stores blood: _____________________
15. The largest organ in the
body cavity: _____________________