It is a description of the bone disposition in the arm, two specific areas can be distinguished, the area that is before the elbow crease is called the arm, it is made up of a single bone known as the “humerus”, for Its part, the area located after the elbow to the wrist is called the forearm, unlike the arm it is made up of two parallel bones, internally is the ulna and in the outermost region the radius. Thus, the arrangement of both bones allows the forearm to rotate without difficulty.
The ulnar bone, as mentioned above, constitutes the internal bone of the forearm, this is an even bone (right and left), however it lacks symmetry, it belongs to the group of long bones, which allows the distinction of the distal areas and the body of the bone. The ulna has a diameter that will progressively decrease along the arm, for the anatomical study of this bone piece in a didactic way, three faces can be identified: anterior face, shows an interconnecting channel of three specific regions, in the part upper allows insertion of flexor muscleThis is responsible for the movement of the finger, while the pronator muscle is inserted in the lower area. The posterior face of the ulnar bone is traversed from bottom to back by a line, just below this line a distinction is made between two regions, the internal region where the ulnar muscle is inserted, and an external region where supinator muscles are housed, specifically located below the conjugating muscles of the forearm.
Finally, on the inner side of the ulnar bone, the upper part of this area is surrounded by a muscle called the "common flexor", which participates in the contraction of the fingers, the lower area of this face is not covered by muscles, only It will be surrounded by aponeurosis (muscle envelope layer) and the most superficial layer called skin. in turn, in the ulnar bone three types of borders can be observed, called anterior, posterior and external.
