Frog Dissection
Place Frog in Pan • Place him/her in the dissection pan. The frog should be lying on his dorsal (back) side with his belly facing up.
Pin the Frog • To secure the frog for the dissection, pin each of his four limbs to the pan.
Begin the First Skin Incision • Once the legs of the frog are securely pinned to the dissection tray you can start your first incision: • Use the forceps to lift the skin midway between the rear legs of the frog. • Using the scalpel, make a small cut through the lifted skin. • This cut should be made in the along the center, or midline, of the frog, bisecting it equally.
Continue Skin Incision • Now, using the scissors, continue the incision up the midline all of the way to the frog's neck. Be very careful not to cut too deeply.
Finish the First Skin Incision • When your scissors reach the frog's neck, you have cut far enough.
Cut Above Front Legs • Using either the scissors or the scalpel, make horizontal incisions through the skin between the front legs.
Cut Above Rear Legs • Still using either the scissors or the scalpel, make horizontal incisions through the skin just above the rear legs.
Separate Skin & Muscle • Once you have finished the incisions between the front and rear legs of the frog you need to separate the skin flaps from the muscle below. To do this: • Pick up the flap of skin with the forceps, and • Use a scalpel to help separate the skin from the muscle below.
Pin Skin Flaps • Once you have finished the incisions between the front and rear legs of the frog you need to separate the skin flaps from the muscle below. To do this: Pick up the flap of skin with the forceps, and Use a scalpel to help separate the skin from the muscle below
Begin 1st Muscle Incisions • Begin the incisions in the abdominal muscles in the same way as when cutting through the skin: • Use the forceps to lift the muscle midway between the rear legs of the frog. • Use the scalpel to start the incision in the direction of the chin
Continue Muscle Incision • Now, using the scissors, continue the incision up the midline all the way to the frog's neck. Be careful not to cut too deeply. The muscle is thin and you don't want to damage the organs underneath
Turn Scissor Blades • This is very important. When you reach a point just below the front legs, turn the scissor blades sideways to cut through the bones in the chest. This should prevent damage to the heart or other internal organs
Finish 1st Muscle Incision • When your scissors reach a point just below the frog's neck you have cut far enough.
Make 2nd Muscle Incisions • Next, using either the scalpel or scissors, make horizontal incisions through the muscle between the front legs.
Second Muscle Incisions • Still using either the scissors or scalpel, make horizontal incisions just above the back legs.
Separate Muscle & Organs • To open up the abdominal area you need to pull back the muscle flaps. To do this: • Hold the flaps of the muscle with forceps, and • Use a scalpel to separate the muscle from the tissues below.
Pin the Muscle Flaps • Once the muscle flaps have been separated from the underlying tissue, they must be pinned back. This will allow easy access to the frog's internal organs.
Open Triangular Flaps • To finish opening up the frog's body cavity, fold back the triangular flaps of skin and muscle which are above the front legs. To do this: • Hold the flap of muscle and skin with the forceps, and • Use a scalpel, if necessary, to help separate the flaps from the underlying tissues.
Pin the Triangular Flaps • As above, once the muscle flaps have been separated from the underlying tissue, they must be pinned back to allow access to the body cavity.
Liver • You are now at the first layer of the dissection. At this point you will be able to see the entire liver and heart. • The liver is a large, brownish colored organ covering most of the body cavity. In the pictures above it is circled by a yellow border.
Heart • The heart is a small triangular shaped organ between the front legs and anterior to the liver. In the pictures above it is circled by a yellow border.
Stomach and Intestines • The “J” shaped organ held by the forceps.
Gall Bladder • When you raise the liver up you will see a small, greenish sac underneath it. This is the gall bladder. In the pictures above it is circled by a yellow border.
Stomach • The stomach is a large, firm, sac-like organ on the left side of the frog. In the pictures above it is circled by a yellow border.
Small Intestine • The small intestine is a long, folded, tube-like organ that is posterior to (below) the stomach. It is similar in color to the stomach, but smaller in diameter. In the pictures above it is circled by a yellow border.
Lungs • The lungs are at the anterior end of the body cavity on either side of the heart. In a preserved frog, they are small, reddish-pink organs. The frog's left lung is circled in each of the pictures above
Ovaries • Found in female frogs only. Locate the ovaries. They are dark organs which may fill most of the frog's body cavity, depending on the time of year that the frog was collected.
Frog Fat
