Since sharks' skeletons are made up of cartilage they belong to a group of fish called Elasmobranchs. Sharks are also cold-blooded which means that their body temperature changes along with their external conditions. Sharks have 5-7 gills and 2 spiracles that absorb oxygen from the water. They are able to eat their prey whole because their jaw is not fused to their brain case. To digest their food, sharks have a U-shaped stomach and spiral shaped intestines. Unlike bony fish, sharks don’t drink water, they absorb it through osmosis instead. A shark’s pectoral fins can't bend upwards which limits their ability to forward motion. Instead of a gas-filled bladder to keep them afloat, a shark has an oily liver. They have keen sense of smell and very poor eyesight. Sharks can sense vibrations in the water using a system of neuromasts called the lateralis system. Sharks are also sensitive to low frequency sounds.
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A shark's brain and S-shaped heart are both located in the head region. Sharks have the ability of detecting electricity because they have jelly-filled canals in their head called the Ampullae of Lorenzini.