Internal Anatomy of the Frog Keep in mind the following questions… To which system does it belong? What is the main function? How is it connected to other organs in the system? How does its form & structure relate to its function?

Dissection of the Frog Lay the frog in the dissection tray, ventral side up, anterior end away from you. Once the legs of the frog are securely pinned to the dissection tray you can start your first incision.

Begin the First Skin Incision Use the forceps to lift the skin (or pinch) midway b/w the rear legs of the frog. Using the scapel, make a small cut through the lifted skin. This cut should be made along the midline of the frog bisecting it equally.

Continue Skin Incision 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 & Rear Legs Using either the scissors or the scapel, make horizontal incisions through the skin between the front legs. Still using either the scissors or the scapel, make horizontal incisions through the skin just above the rear legs.

Separate Skin & Muscle Once you have finished the incisions between the front & rear legs of the frog you need to separate the skin flaps from the muscle below. Pick up the flap of skin with the forceps Use a scalpel to help separate the skin from the muscle below.

Pin Skin Flaps Once the skin flaps have been cut back to the point pictured here, all you need to do is pin them to the dissection tray.

First Muscle Incision 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 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 & 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 Incision Next, using either the scapel or scissors, make horizontal incisions through the muscle between the front legs. 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. Hold the flaps of the muscle with forceps Use a scalpel to separate the muscle from the tissues below.

Pin the Muscle Flaps Once the muscle flaps have been separted from the underlying tissue, they must be pinned back. This allows 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 & muscle which are above the front legs. Pin back to allow access to the body cavity.

Some Internal Anatomy Images Remember to ask yourself: To which system does it belong? What is the main function? How is it connected to other organs in the system? How does its form & structure relate to its function?

Male Frog a. Large intestine. b. Small intestine. 1. Lung lobes. 2. Heart. 3. Liver lobes. 4. Gall bladder. 5. Stomach. 6. Small intestine 7. Testis 8. Fat body 9. Urinary bladder

Female Frog 1. Liver lobes. 2. Heart. 3. Ovary with eggs. 4. Gall bladder. 5. Small intestine. 6. Stomach. 7. Oviduct.

Small Intestine

Liver

Ovaries

Stomach

Resources Virtual Tutorial www.curry.edschool.virgina.edu/go/frog/skin/home.html