The radius and the ulna are long, slightly curved bones that lie parallel from the elbow, where they articulate with the humerus, to the wrist, where they articulate with the carpals. The radius is located laterally, near the thumb, and the ulna medially, near the little finger. The radius and the ulna have a styloid process at the distal end; they are also attachment sites for many muscles.The radius is smaller than the ulna.
A total of 27 bones constitute the basic skeleton of the wrist and hand. These are grouped into carpals, metacarpals, and phalanges.
The wrist is the most complex joint in the body. It is formed by 8 carpal bones grouped in 2 rows with very restricted motion between them. From radial to ulnar, the proximal row consists of the scaphoid, lunate, triquetrum, and pisiform bones. In the same direction, the distal row consists of the trapezium, trapezoid, capitate, and hamate bones.
The hand contains 5 metacarpal bones. Each metacarpal is characterized as having a base, a shaft, a neck, and a head. The first metacarpal bone (thumb) is the shortest and most mobile. It articulates proximally with the trapezium. The other 4 metacarpals articulate with the trapezoid, capitate, and hamate at the base. Each metacarpal head articulates distally with the proximal phalanges of each digit.
The hand contains 14 phalanges. Each digit contains 3 phalanges (proximal, middle, and distal), except for the thumb, which only has 2 phalanges. To avoid confusion, each digit is referred to by its name (thumb, index, long, ring, and small) rather than by number.
This is 3D printable medical file converted from a CT scan DICOM dataset of a 48-year old female.