Teeth & Jaws
Shark teeth are formed from specialized skin tissue on the jaw cartilage. Teeth are arranged in rows and attached to the jaws by connective tissue. Usually only the front one or two rows are functional. The other teeth, in some cases up to 13 rows, are folded back against the inside of the jaw, where they develop.
As the connective tissue moves slowly forward, new teeth continuously replace older ones as they are lost or just fall out. Lost teeth can sometimes be replaced in as little as 24 hours. Some sharks may shed 50,000 teeth in a lifetime. Not all sharks shed their teeth one or two at a time. The cookiecutter shark sheds its entire lower plate of teeth at once, often swallowing the teeth with its meal.
Each species of shark has its own distinctively shaped teeth, although the teeth of some species are very similar. Comparing some local species, the tiger shark has notched, serrated teeth on both jaws; the mako shark has dagger-like teeth and the white shark has serrated triangular teeth.
Tooth shape, size, and structure vary with a shark’s primary food source. Teeth may be designed to grasp, tear, or cut. In some sharks teeth are modified to grind or crush mollusks or crustaceans.
Nearly all sharks have what is known as a subterminal mouth, located on the ventral surface (underside) of the head behind the snout. The upper jaw is suspended below the skull, attached by ligaments, muscle, and connective tissue. The lower jaw is connected to the upper jaw at the corners of the mouth and attached to massive muscles used for biting.
Each jaw is somewhat flexible, consisting of right and left halves joined in the center at what is termed the symphysis. During a bite, many sharks can extend the entire jaw structure forward, thrusting it out from the skull. This helps some sharks bite off parts of prey that are too big to swallow whole.
The pressure exerted by shark jaws has been measured at around 42,000 pounds per square inch. This is actually about the same order of magnitude as the pressure humans can exert with their molars. But because shark teeth are so sharp, their biting force is distributed over a much smaller surface area, and as a result can do considerably more damage than human teeth.