The hand contains 27 bones. Each one belongs to one of three regions: the carpals, (wrist), the metacarpals, (the
palm), and the phalanges (the digits).
The eight, irregularly shaped carpals are
the most proximal bones of the hand. The carpals are often split into two rows,
the proximal row containing the scaphoid, lunate, triquetrum, and pisiform,
moving lateral to medial.
The scaphoid and lunate articulate with the radius,
and the lunate and triquetrum articulate with the articular disk of the wrist.
The pisiform carpal is a sesamoid bone, located within a tendon and is not
involved in movement at the wrist.
The distal row contains the trapezium,
trapezoid, capitate, and hamate, moving lateral to medial. The trapezium
articulates with the scaphoid proximally and the first, thumb, and second
metacarpal distally. The trapezoid articulates with the scaphoid proximally and
the second metacarpal distally. The capitate articulates with the scaphoid and
lunate proximally and the third and fourth metacarpal. Finally, the hamate articulates
with the lunate and triquetral proximally and the fourth and fifth, little
finger, metacarpals distally.
The hand contains five metacarpal bones that articulate proximally with the carpals and distally with the proximal
phalanges. They are numbered moving lateral to medial, and start with the thumb,
which is metacarpal I, and end with metacarpal V, the little finger.
metacarpal consists of a base, shaft, and head, with the concave lateral and
medial borders of the shaft allowing attachment of the interossei muscles.
The digits are named in a
similar fashion to the metacarpals, moving lateral to medial, and starting at the
thumb. With the exception of the thumb, each digit contains a proximal,
intermediate, and distal phalange; the thumb lacks an intermediate phalange. The
length of the phalanges decreases distally.