What are Dermal Denticles?

The texture of a shark's skin is rough since it consists of small scales called "dermal denticles".  Each species of shark has a unique shaped denticle. They have a covering of dentine, which is a central pulp canal containing blood vessels and a single nerve. If you rub your hand along the body of a shark from front to back, there is little resistance and it feels relatively smooth. However, when you rub your hand back to front, the skin feels like rough sand paper. The denticles play an important part in swimming efficiency. Water is channeled by the denticles, flowing across the fins and around the body, while also breaking up the interface between skin and water. This reduces the friction between the two entities. Dermal denticles also help protect sharks from injuries and several elements in the water, like a suit of armor.