The human hand is a complex structure composed of bones, tendons, muscles, blood vessels and nerves. Hands must master both gross motor skills (grabbing a tree branch or a bat) and fine motor skills (grabbing a pen and writing). There are 27 bones in each hand.
Carpal Bones
There are eight carpal bones, which, in combination with the distal aspects of the radius and the ulna (the bones of the forearm) form the wrist. The eight carpal bones fit into a shallow socket of the radius and ulna in two lines. The proximal line (closer to the forearm) contains the scaphoid, lunate, triquetral and pisiform bones. The distal line (closer to the palm of the hand) contains the trapezium, trapezoid, capitate and hamate.
Metacarpal Bones
The five metacarpal bones form the palm of the hand. Each bone is divided into descriptive (but not anatomical) parts: a head, a shaft, and a base. A fracture of the fifth metacarpal, right below the little finger, is described as a "boxer's fracture;" the mechanism of the fracture, as the name implies, is a punch on a hard surface.
Phalanges
The digits, or phalanges, are each composed of phalanx bones. Each finger contains three bones, except the thumb, which only contains two, for a total of 14 digital bones in each hand. The phalanges are divided into proximal phalanx, middle phalanx, and distal phalanx. The distal phalanx contains the nail bed.
A common injury in the phalanges is a dislocated proximal interphalangeal (PIP) joint, the joint in between the proximal and middle phalanx. It usually occurs as a result of a jamming-type injury. This kind of injury usually requires the expertise of a hand or orthopedic surgeon to prevent long-term complications.
