Click on a number for a description of the corresponding part.
1. Nostril -- As a shark swims along, water flows into its nostrils and enters the nasal sacs. The nasal sacs are sensitive scent organs, and sharks can detect very weak odors. A shark can smell a drop of blood in 25 gallons of seawater.
2. Ampullae of Lorenzini -- Small pits covering large areas of skin near the mouth and nose below the shark's snout. They are natural electrical sensors which, at close range, can detect weak electrical fields generated by all animals.
3. Eye -- Most sharks have a well-developed sense of vision. They see better at night than most humans, and research suggests that some species can see color. Sharks have upper and lower eyelids, but these lids don't move. Some sharks have a membrane, the nictitating eyelid, that can be closed over the eye to protect it from damage.
4. Dermal denticles -- Shark skin is covered by a layer of small tooth-like structures called dermal denticles. As the shark grows, the denticles are shed and replaced by slightly larger ones. The layer of dermal denticles creates a rough surface that is sometimes compared to sandpaper. Untanned shark skin, called shagreen, is used to sand and polish furniture.
5. First dorsal fin -- Most sharks swim by thrusting their tail fins from side to side. The unpaired first dorsal fin, along with the smaller second dorsal and anal fins, keeps the shark's body stable as it swims through the water.
6. Countershading -- This is a form of protective coloration in which animals are darker on their upper (dorsal) surface than on their lower (ventral) surface. Many sharks, especially those that live near the surface, are a a dark color on their backs and a lighter color on their bellies. The countershading camouflages them from two directions -- looking up at them against the surface, and looking down at them against the sea floor.
7. Lateral line -- The lateral line is a network of sensory hair cell clusters (neuromasts) and small water-filled canals that lie immediately beneath the skin on a shark's head and extend along the sides of its body. This network is sensitive to external motion, and helps the shark detect prey and potential predators.
8. Second dorsal fin -- The unpaired second dorsal fin assists in thrust as the shark swims, and helps stabilize it, preventing it from rolling from side to side as it swims. Not all sharks has a second dorsal fin.
9. Caudal fin -- The caudal fin is the tail fin. In sharks, the caudal fin is heterocercal which means it has an upper lobe that is usually larger than the lower one. In fast sharks like the mako and the great white, the lobes are almost equal. In the thresher shark, the upper lobe can be almost as long as its body.
10. Anal fin -- Small, unpaired fin on the posterior of the shark's body. They are important for stability as the shark swims.
11. Pelvic fin -- Paired fins, located on the posterior of the sharks body. In male sharks, the paired pelvic fins have rod-like extension on the inner edge. These extension are used as claspers during internal fertilization.
12. Pectoral fin -- The paired pectoral, located just behind or below the gill slits, are used for lift during swimming and for turning.
13. Gill slits -- These are the slit-like openings behind a shark's head. Most sharks have five pairs of gill slits, but some have six or seven pairs. As a shark breathes, oxygen-rich water enters its mouth. The water passes over the gills and respiration takes place: oxygen in the water is exchanged for carbon dioxide in the blood. The now oxygen-depleted water exits through the gill slits.
14. Teeth -- Most sharks have 5 to 15 rows of teeth in each jaw. When a tooth falls out, there's already a tooth waiting to replace it. The new tooth moves forward as though on a conveyor belt. A missing tooth can be replaced in as little as 24 hours.
15. Jaws -- In most sharks, the mouth is beneath the snout. The jaws are loosely connected by ligaments and muscles to the skull, and are very mobile. When a shark starts to bite, its snout bends up and out of the way. The jaws move forward and protrude. When the shark bites its prey, the jaws move back and under the snout again. This happens very quickly.