Finger

A finger is an elongated digit extending from the hand or foot. Humans typically have five fingers on each hand and five on each foot, for a total of twenty. The fingers of the hand are used for grasping, holding, and touching; those of the foot assist with balance and walking.

Fingers are made up of small bones called phalanges. Most fingers have three bones, except the thumb and big toe, which have two. These bones are connected by joints that allow for bending and straightening.

Structure

Fingers have no large internal muscles. Their movement is powered by muscles located in the forearm and palm, connected to the fingers by long tendons. When these muscles contract, the tendons cause the fingers to bend or straighten. The outer layer of each finger is made of keratin, which covers the tip of the digit.

Sensation

The skin of the finger, especially that of the palm, contains a very high number of sensory receptors. This makes the fingers among the most sensitive parts of the body to touch and temperature. The skin on the fingers also contains ridges unique to each person, which are used for identification.

Grasping and Holding

The human thumb can be fully opposed to the other fingers—a property known as opposability. This allows for the grasping and precise manipulation of small objects, which is fundamental to tool use. This property also exists in other primates and some mammals, though to varying degrees.

Variation Across Species

Finger bones follow the same basic pattern seen in many vertebrates, though their function varies. The wings of birds, the fins of fish, and the legs of horses all stem from the same ancestral structure, but the number and length of the bones have changed. Horses, for example, walk on a single enlarged digit that everyone recognizes as a hoof.