In essence, they slowly suffocate the prey, causing difficulties in breathing and swallowing and disrupting work of the heart. Hemotoxins damage blood vessels and body tissues. The location of the fangs is usually in the front of the mouth while other groups use their back teeth as fangs. Most poisonous snakes are front fanged and use the two teeth closest to the front of the mouth in the upper jaw to inject their venom. Based on the type of fangs poisonous snakes may be further classified into vipers and elapids.
Vipers have long, movable fangs and included copperheads and rattlesnakes.
When the fangs aren't in use they fold back into a sheath on the roof of the mouth. Elapids, which include cobras and coral snakes, have short front fangs that are fixed in place. A narrow tube connects each fang to the venom gland on each side of the upper jaw. The fangs in poisonous snakes are similar to hypodermic needles and are usually shed and replaced several times a year. For years, scientists have studied various species of snakes in hopes of understanding their living behavior and developing different antidotes or serums for different snakebites.