Reference > Anatomy of the Human Body > Page 454
Henry Gray (1825–1861).  Anatomy of the Human Body.  1918.
passing from the same tendon downward and medialward to the fourth. Occasionally the first tendon is connected to the second by a thin transverse band.

Variations.—An increase or decrease in the number of tendons is common; an additional slip to the thumb is sometimes present.
  The Extensor digiti quinti proprius (Extensor minimi digiti) is a slender muscle placed on the medial side of the Extensor digitorum communis, with which it is generally connected. It arises from the common Extensor tendon by a thin tendinous slip, from the intermuscular septa between it and the adjacent muscles. Its tendon runs through a compartment of the dorsal carpal ligament behind the distal radio-ulnar joint, then divides into two as it crosses the hand, and finally joins the expansion of the Extensor digitorum communis tendon on the dorsum of the first phalanx of the little finger.

Variations.—An additional fibrous slip from the lateral epicondyle; the tendon of insertion may not divide or may send a slip to the ring finger. Absence of muscle rare; fusion of the belly with the Extensor digitorum communis not uncommon.
  The Extensor carpi ulnaris lies on the ulnar side of the forearm. It arises from the lateral epicondyle of the humerus, by the common tendon; by an aponeurosis from the dorsal border of the ulna in common with the Flexor carpi ulnaris and the Flexor digitorum profundus; and from the deep fascia of the forearm. It ends in a tendon, which runs in a groove between the head and the styloid process of the ulna, passing through a separate compartment of the dorsal carpal ligament, and is inserted into the prominent tubercle on the ulnar side of the base of the fifth metacarpal bone.

Variations.—Doubling; reduction to tendinous band; insertion partially into fourth metacarpal. In many cases (52 per cent.) a slip is continued from the insertion of the tendon anteriorly over the Opponens digiti quinti, to the fascia covering that muscle, the metacarpal bone, the capsule of the metacarpophalangeal articulation, or the first phalanx of the little finger. This slip may be replaced by a muscular fasciculus arising from or near the pisiform.
  The Anconæus is a small triangular muscle which is placed on the back of the elbow-joint, and appears to be a continuation of the Triceps brachii. It arises by a separate tendon from the back part of the lateral epicondyle of the humerus; its fibers diverge and are inserted into the side of the olecranon, and upper fourth of the dorsal surface of the body of the ulna.

The Deep Group (Fig. 419).
Extensor pollicis brevis.
Abductor pollicis longus.
Extensor pollicis longus.
Extensor indicis proprius.
  The Supinator (Supinator brevis) (Fig. 420) is a broad muscle, curved around the upper third of the radius. It consists of two planes of fibers, between which the deep branch of the radial nerve lies. The two planes arise in common—the superficial one by tendinous and the deeper by muscular fibers—from the lateral epicondyle of the humerus; from the radial collateral ligament of the elbow-joint, and the annular ligament; from the ridge on the ulna, which runs obliquely downward from the dorsal end of the radial notch; from the triangular depression below the notch; and from a tendinous expansion which covers the surface of the muscle. The superficial fibers surround the upper part of the radius, and are inserted into the lateral edge of the radial tuberosity and the oblique line of the radius, as low down as the insertion of the Pronator teres. The upper fibers of the deeper plane


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