Snake Dissection

<<Dissection Tools & Kits

One practical way to see for yourself how an amphibian and reptile differ is to compare the anatomy of two species, such as a frog and a snake. Although you can observe the external anatomy on live ones at a pet store or in the wild, it's hard to discover anything about their insides without doing a dissection.

Even if you don't want to dissect a snake (or a turtle, for another interesting reptile specimen), you might find the following description of a snake's anatomy helpful. You can compare it to our online frog dissection guide, with pictures and detailed instructions. (You can also find virtual frog dissections online, instead of doing your own.) This is an ideal project for junior high and high school students who are studying animal classification.

Snake Anatomy

Click this link for a printable snake dissection diagram with labeled parts (.pdf). Use this as a guide for locating organs.

Inspect the external anatomy of the snake. Why do you think the scales on the specimen's back (dorsal side) are different than the scales on its belly (ventral side)? The ventral scales correspond to the number of ribs that the snake has and allow greater flexibility of movement.

Make a long incision down the center of the ventral surface, from the cloacal opening to the throat. Carefully pull back the skin and pin it down on either side, cutting the membrane layer underneath as necessary. Once the snake is opened, observe how it looks inside. Then slice the membrane away until it separates from the organs. (This membrane holds the organs securely in place in the living snake.) This is the longest part of the dissection process, but go slowly and cut carefully.

Identify the major organs listed below. The heart, stomach, gallbladder, liver, and large and small intestine will probably be the easiest to find. These are listed in order roughly from head to tail.

Trachea: A dark-colored tube in throat that brings air to the lung.
Heart: Located just below trachea. It is a three-chambered like a frog heart.
Right lung: Most snakes have only one functioning lung, a long narrow sac starting near the heart. Look for it between the liver and stomach. The specimen might also have another, smaller lung.
Liver: A long, thin orangish-colored organ on the left side (as you look at it).
Stomach: A long sac that connects to the esophagus in the throat and small intestine lower down. Is your specimen's stomach empty or full? If full, you might want to check out the contents to discover what the snake was eating.
Gallbladder & pancreas: The gallbladder is small and round, usually greenish-colored from the bile for digestion stored in it. You might have to remove some of the yellow fat bodies to see it. (A healthy snake will have many fat bodies.) The pancreas looks just like an extension of the intestine, right next to the stomach.
Small & large intestine: The small intestine starts right below the stomach and forms many coils.
Gonads: These might look similar to the intestine, but are not connected to it. Male snakes are identifiable by testes inside and hemipenes at the cloacal opening. Females have a pair of ovaries and might have eggs. (If both the frog and snake specimens have eggs, be sure to compare them!)
Kidneys: These are located near the end of the large intestine; they should be similar in color to the intestine, but if you look closely you'll see that they are a different kind of tissue.