FORE-ARM, (Surgical anatomy), ( Anti brachium ; Fr. Avant-bras; Germ. der ['ore/cr am). This term is applied to that portinn of the upper extremity which is situated be tween the elbow and wrist-joint.
In the well-formed male all the muscles of this region, but especially the snpinators, from the fascia which covers them being extremely thin, when thrown into action stand out in strong relief, giving an appearance of great power concentrated within a small space. In the female, on the contrary, the fore-arm, from the great preponderance of adipose tissue, presents a swelling outline and rounded form, not the less beautiful, perhaps, from indicating deficiency of muscular energy, and conveying the idea of softness and dependence.
The usual and least constrained position of the fore-arm is with the hand between prona tion and supination, that is, with the palm of the hand inwards and the dorsum outwards; but for the purpose of anatomical description the palm of the hand is supposed to face for wards and the dorsum backwards, the fore-arm being extended. In this position the fore arm obviously differs from the arm in being wider from side to side than from before back wards. Superiorly it presents in front a very slightly convex surface, but inferiorly there is formed by the flexor tendon a distinct central projection, which is bounded by the flexor carpi radialis on the radial side, and by the flexor carpi ulnaris on the ulnar.
The posterior surface of the fore-arm is more irregularly convex than the anterior; the greatest convexity is nearer the ulnar than the radial edge, and is formed by the olecranon above and the shaft of the ulna below, which is covered only by the skin superiorly. A con siderable depression may be observed, bounded on the inner side by the olecranon, and on the outer by the supinators; in this depression the outer condyle may be felt. To the inner side of the olecranon there is a corresponding but much smaller depression, in which the inner condyle is situated. For about three inches above the wrist-joint the fore-arm pos teriorly is slightly concave in the centre in consequence of the marked projection of the ulna and radius on either side. In the motions
of pronation and supination the shape of the fore-arm is considerably changed ; but as no practical advantage can attend a detailed ac count of the changes undergone, we shall not dwell upon them here.
The parts composing the fore-a•m are as fol low: the radius and ulna, the muscles of the hand and fingers, the radial and ulnar arteries with their branches, the vent': satellites of these arteries and the subcutaneous veins, the radial, ulnar, median, and cutaneous nerves, the ab sorbent vessels, a quantity of cellular and adipose tissue, various aponcuroses, and the common integuments.
The configuration, relative position, and connection of the bones of the titre-arin have been described in the article r arm ITY. They move together in the flexion and exten sion of the fore-arm on the os humeri at the elbow-joint, under the influence of the biceps flexor cubiti and brachialis anticus, and the triceps extensor cubiti and anconeus.
In the motions of supination and pronation the radius is always rolled upon the ulna, the latter remaining perfectly fixed, though this fact has been disputed in consequence of the thick sacciform ligament of the wrist and the tendon of the extensor carpi °Maris being felt to roll under the finger when placed on the inferior extremity of the ulna during the motion of rotation and supination, and thus communicating the sensation of a motion in the ulna itself.
The skin of the fore-arm differs considerably on the dorsal and anterior aspects. On the former it is coarse and comparatively rough, containing numerous small hairs ; on the latter it is smooth and more delicate, and the adipose tissue being more abundant on the anterior, the whole surface is more even, while on the posterior the extensor muscles of the hand and fingers, being slightly covered, project considerably. Neither of the regions, however, contain so much fat as most other parts of the body.