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The forearm is the region of the upper limb between the elbow and the wrist. [1] The term forearm is used in anatomy to distinguish it from the arm, a word which is used to describe the entire appendage of the upper limb, but which in anatomy, technically, means only the region of the upper arm, whereas the lower "arm" is called the forearm.
The ulna or ulnar bone (pl.: ulnae or ulnas) [3] is a long bone in the forearm stretching from the elbow to the wrist. It is on the same side of the forearm as the little finger, running parallel to the radius, the forearm's other long bone. Longer and thinner than the radius, the ulna is considered to be the smaller long bone of the lower arm.
The radius or radial bone (pl.: radii or radiuses) is one of the two large bones of the forearm, the other being the ulna. It extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna. The ulna is longer than the radius, but the radius is thicker.
It is composed of 270 bones at the time of birth, [2] but later decreases to 206: 80 bones in the axial skeleton and 126 bones in the appendicular skeleton. 172 of 206 bones are part of a pair and the remaining 34 are unpaired. [3] Many small accessory bones, such as sesamoid bones, are not included in this.
Predators hunting prey that is half their body weight or greater evolved shorter and more sturdy radii, ulnas, and humeri to decrease the likelihood of the bone breaking or fracturing while hunting. Predators hunting prey less than half their body weight tended to have longer and more slender forelimb long bones to improve energetic efficiency. [7]
The forearm (Latin: antebrachium), [5] composed of the radius and ulna; the latter is the main distal part of the elbow joint, while the former composes the main proximal part of the wrist joint. Most of the large number of muscles in the forearm are divided into the wrist, hand, and finger extensors on the dorsal side (back of hand) and the ...
The olecranon is situated at the proximal end of the ulna, one of the two bones in the forearm. [1] When the hand faces forward the olecranon faces towards the back (posteriorly). It is bent forward at the summit so as to present a prominent lip which is received into the olecranon fossa of the humerus during extension of the forearm. [2] [3]
In human anatomy, the metacarpal bones or metacarpus, also known as the "palm bones", are the appendicular bones that form the intermediate part of the hand between the phalanges and the carpal bones (wrist bones), which articulate with the forearm. The metacarpal bones are homologous to the metatarsal bones in the foot.