The human hand typically has five digits: four fingers and a thumb. The skeleton of each hand is usually formed by 27 bones, not including the sesamoid bones, which are variable in number for each individual.

The bones of the hand can be grouped into three categories:

Carpal bones (8) - most proximal;
Metacarpal bones (5) - forming the middle part;
Phalanges (14) - most distal (including proximal, middle, and distal phalanges).

Metacarpal bones

The metacarpal bones are located between the carpus and the phalanges, forming the middle portion of the skeleton of the hand. This part of the hand skeleton is also known as the metacarpus. The metacarpal bones are analogous to the metatarsal bones in the foot.

Each metacarpal bone consists of three main parts:

Base - the proximal or carpal end;
Body (shaft) - the middle part of a bone;
Head - the distal or digital end.

Phalanges of hand

The phalanges are bones of fingers that are found in both hands and feet. There are fourteen phalanges in each hand. The human thumb has two phalanges - proximal and distal, while the rest of the digits each has three - proximal, middle, and distal phalanges.

The three phalanges of each finger articulate with one another, forming interphalangeal joints. The proximal phalanges also articulate with the metacarpal bones of the hand to form metacarpophalangeal joints.

The phalanges are long bones, and each phalanx consists of three parts:

Base - the proximal extremity; the base of each phalanx of the first row presents oval, concave articular surface, while the bases of second and third row phalanges each presents a double concavity separated by a median ridge;
Body - the middle part, which is concave on the palmar surface and convex on the dorsal surface, while the sides of the body have rough areas for attachment of fibrous sheaths of flexor tendons;
Heads - the distal extremities of phalanges; smaller than the bases, each ends in two condyles (known as knuckles).

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Metacarpal bones and phalanges