The five-rayed anterior limbs of terrestrial vertebrates can be derived phylogenetically from the pectoral fins of fish. Within the taxa of finger food terrestrial vertebrates, the basic pentadactyl plan, and thus also the fingers and phalanges, undergoe many variations. In the case of Primates in general, the digits of the hand are overwhelmingly referred to as “fingers”.
The term fingers is used for canines, felines and ungulates only in comparative morphology, not in colloquial language, because they have paws or forelegs with hooves, none of which can engage in fine manipulation with their forelimbs as a primate can. The palm has five bones known as metacarpal bones, one to each of the five digits. These are the distal phalanx, carrying the nail, the middle phalanx, and the proximal phalanx. Joints are formed wherever two or more of these bones meet. Sesamoid bones are small ossified nodes embedded in the tendons to provide extra leverage and reduce pressure on the underlying tissue. The articulations are: interphalangeal articulations between phalangeal bones, and metacarpophalangeal joints connecting the phalanges to the metacarpal bones.
Each finger may flex and extend, abduct and adduct, and so also circumduct. The muscles that move the finger joints are in the palm and forearm. The long tendons that deliver motion from the forearm muscles may be observed to move under the skin at the wrist and on the back of the hand. Muscles of the fingers can be subdivided into extrinsic and intrinsic muscles.