Teeth
A dolphin's teeth aren't used for chewing -- it swallows food whole -- but they do help it grab prey. Some scientists also think the teeth are spaced in such a way to help the dolphin analyze sound waves that bounce back to it from an object.

Melon
This is the fatty, rounded section of a dolphin's forehead, and it's critical to its extremely sensitive and complex use of echolocation. The melon acts as an acoustical lens to focus sound waves into a beam that is projected in front of the animal.

Dorsal fin
A dolphin's dorsal fin is cartilage that can be as distinctive as a human's face and is used by scientists to identify individuals. Dolphins that have dorsal fins -- not all do -- seem to use them for stability.

Eyes
Dolphins come equipped with elastic lenses on their eyes that expand and contract to let them focus both above and below the water. And they have special glands that protect their eyes from salt water.

Skin
Like human skin, dolphin skin has many nerve endings, which explains why tame dolphins like to be stroked. Dolphin skin is also extremely delicate and easily injured by rough surfaces. It can be cut by a sharp fingernail, but tends to heal quickly.

Blowhole
The blowhole serves as a dolphin's nostrils, allowing it to breathe while swimming at top speed. To breathe while asleep, female dolphins lie on the water's surface with their blowholes exposed to the air; males sleep just below the surface and rise to breathe periodically as a reflex action.