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Thursday, January 5, 2012

Skeletal/Muscular System

Size- The GWS is not the largest shark, but comes in third behind the whale shark and the Basking Shark. But the GWS is fiercest shark while the other two are harmless plankton eaters. The great white average about 20 ft long and about 4200 lbs.

Skeleton- The skeleton of a shark is mainly cartilage. The sharks have at least 230 bones. Cartilage is flexible and durable, yet has about half the density of bone. This reduces the skeleton’s weight, saving energy. The shark has no rib cage, therefore on land a shark can crush itself.

Teeth- Shark teeth are embedded in the gums rather than directly affixed to the jaw. They are constantly replaced throughout life. Multiple rows of replacement teeth grow in a groove on the inside of the jaw and steadily move forward as in a "conveyor belt". Sharks can lose 30,000 or more teeth in their lifetime. The rate of tooth replacement varies from once every 8–10 days to several months. GWS have needle-like teeth for gripping, and those that feed on larger prey such as mammals have pointed lower teeth for gripping and triangular upper teeth with serrated edges for cutting. Shape of the tooth depends on their diet.

Jaw- The sharks jaw is not attached to the cranium.The jaw's surface arches because it needs extra support due to its heavy exposure to physical stress and its need for strength

Fins-  Fin skeletons are elongated and supported with soft and unsegmented rays named ceratotrichia. Most sharks have eight fins. Sharks can only drift away from objects directly in front of them because their fins do not allow them to move in the tail-first direction.

Tails-  The tail provides thrust, making speed and acceleration dependent on tail shape.

Dermal Denticles- Unlike bony fish, sharks have a complex dermal corset made of collagenous fibers and arranged as a helical network that surrounds their body. This works as an outer skeleton, providing attachment for their swimming muscles and saving energy as well.

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