Keratin based elements (ceratotrichia) support the fins and is what shark fin soup is made from. It looks like dry spaghetti running through the fin.

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The vertebral column passes into the upper lobe of the tail, this is a heterocercal tail. The upper lobe is usually much longer than the lower lobe, however in fast swimming species like the shortfin mako and the great white, the lower lobe is enlarged too but the tail is still internally heterocercal. The caudal peduncal is where the narrowing of the body meets the tail. All the force generated by the sharks muscles is translated to the tail via the caudal peduncal. In general, the body shape of a shark will determine their lifestyle. Fast swimming, open ocean species like the shortfin mako and great white have a conical head, large thick body, large pectoral fins, a narrow caudal peduncal with keels and symmetrical caudal fin. This is the most efficient body shape for moving quickly though the water. More moderate swimmers like blue sharks and tiger sharks have a more flattened head, thinner body, thicker caudal peduncal with little or no keels, large pectoral fins and an upper lobe which is larger than the lower lobe. These sharks have the broadest range of swimming speeds. Slow swimming sharks like the nurse and leopard sharks have large heads with blunt snouts, pelvic fins positioned more forward, dorsal fins set farther back and a highly asymmetrical caudal fin with no lower lobe. Sharks that live on the bottom such as angel sharks, have a flattened body, large pectoral and pelvic fins, no anal fin and a reduced tail section.