How to Dissect a Shark

Dogfish sharks are very common animals for dissection because they are small and abundant. Dissecting one is a great way to introduce students to the fascinating adaptations which sharks possess, as well as the basic principles of dissection. Read on to learn how to dissect a shark.

Difficulty:

Moderately Easy

Instructions

Things You'll Need

• Scalpel
• Tweezers
• Gloves

1. Locate the external anatomy. The eyes are the easiest thing to spot. Notice they are on either side of the head, not facing forward. This allows the sharks to see all around themselves in the water.

2. Make an incision along the side of the eye to cut the nictating membrane. This membrane is a thin eyelid that the shark can see through. It protects the animal's eye from injury when it is attacking its prey.

3. Remove the nictating membrane to look at the eye. Shark eyes are very similar to the eyes of other vertebrates, including humans. They contain a lens, a cornea, and a retina

4. Look at the nostrils at the tip of the snouts. Shark nostrils are not connected to their breathing organs. Instead, they have tiny pits inside them that allow the sharks to detect their prey. Sharks rely on their sense of smell more than on any other organs.

5. Look at the small pits behind the sharks eyes. These are called the Ampulae of Lorenzini Dogfish can use these to detect electrical impulses from other animals. This helps them to find prey.

6. Look inside the mouth. Sharks have many rows of teeth which are not attached to their jaws. These teeth are continuously replaced during their lives.

7. On each side of the shark, you can find the gill slits. Notice that the gills are in front of the fins. Sharks must move continuously to keep water moving over their gills, or find an underwater vent. Without moving water, they cannot breathe.

8. Note the fins. Sharks have two pectoral fins near the head for steering, a dorsal fin on the back for stability, a caudal fin, otherwise known as a tail fin, and two pelvic fins between the pectorals and the caudal

9. Begin the internal dissection by making a t cut from the mouth down to the cloaca, and from pectoral fin to pectoral fin across the body. The cloaca is a small hole between the two pelvic fins used for expelling waste and sexual reproduction.

10. Peel back the skin. Either pin it open or remove it.

11. The first organ you will find is the three lobed liver. It is a a large, grayish green organ divided into three sections. There are two big sections on the sides, and a smaller one in the middle. Remove it.

12. The liver filters the blood and cellular waste material. It also keeps the shark buoyant. The liver is very oily, and this oil is lighter than water, helping the shark to float.

13. You will see the internal organs, including the digestive system. The esophagus is connected to the mouth on one end and the stomach on the other end. Sharks only have one intestine, coming out of the stomach. At the end of the intestine is the cloaca.

14. Cut the esophagus at the top and the intestine at the bottom and remove the digestive system. Open the stomach to see if the shark ate recently. Occasionally, you can find preserved fish, not yet digested in the stomach. You can also sometimes find digested food in the intestines.

15. Cut open a section of the intestine. You will see a spiral of tissue called the spiral valve. This pushes the food around, keeping it in constant contact with the walls of the intestine.