A detailed anatomical diagram of a thumb is available from the American Society for Surgery of the Hand, Healthline and Innerbody. The thumb is a unique digit of the hand; medical professionals don't refer to it as a finger.Continue Reading
The thumb is opposable to the other four fingers, and the tip of the thumb can touch the tip of each of the other four digits. Instead of the four phalanges of the other fingers, the thumb only has three.
The thumb is not unique to human beings. Some other primates, such as chimpanzees and gibbons, possess opposable thumbs. Some types of mice also have thumbs. Pandas and marsupials, such as opossums, have digits that act like thumbs.Learn more about Human Anatomy