Eye: Sharks have outstanding eyes that can see in very low light. Some sharks have nictating membranes, which close and protect the eyes when the shark is feeding or close to an object.
Nostril: Unlike humans, sharks don’t breathe through their nostrils. They only use their them for smelling. A shark’s sense of smell is unbelievably strong. It can detect a drop of blood hundreds of feet away.
Teeth: Sharks’ teeth are arranged in rows. The row nearest the front is the “working” row of teeth. Some sharks lose over 30,000 teeth in their lifetime. Every time a shark loses a tooth, the tooth in the row behind replaces it, like a conveyor belt. The teeth are continually being grown and replaced.
The shape of the shark’s tooth depends on what it eats. If it eat fish, the shark has long, narrow teeth for grabbing onto the slippery fish. If it eats crustaceans, it has thick teeth for crushing. Serrated cutting teeth are used for seals and other mammals. Basking and whale sharks have tiny little teeth, since they only eat plankton and krill.
Gill Slits: Sharks do not breathe oxygen from the air, like we do. A shark has have 5-7 gill slits along the sides of their head that do the work. As they swim, the water passes through their mouths and over these gills. Thin-lined blood vessels absorb oxygen from the water.
Spiracle: Spiracles are a pair of openings behind some sharks’ eyes that act like baby gill slits. Sharks that are slow and dwell near the bottom sometimes have spiracles. The shark can draw oxygenated water into the spiracle and breathe even while lying on the bottom of the ocean.
Ampullae of Lorenzini: The ampullae are jelly-filled pores around the head that sense electrical fields. Every living thing creates an electrical field, so the shark can detect another creature without using any of its other senses.
Lateral Line: This is another sensory system that detects low-frequency vibrations in the water.
First and Second Dorsal Fins: This fin helps stabilize the shark. Some sharks have spines on the dorsal fins, which they use to defend themselves against potential predators.
Caudal Fin: This fin is the shark’s tail and moves the shark forward in the water. The upper lobe provides most of the force.
Anal Fin: Some sharks have anal fins for additional stability.
Pelvic Fin: Two pelvic fins stabilize the shark while it swims.
Pectoral Fin: Two pectoral fins lift the shark and help it steer while it’s swimming.