Henry Gray (18251861). Anatomy of the Human Body. 1918.
digital branch for the ulnar side of the little finger, and a common volar digital branch which gives a communicating twig to the median nerve and divides into two proper digital nerves for the adjoining sides of the little and ring fingers (Fig. 811). The proper digital branches are distributed to the fingers in the same manner as those of the median.
The deep branch (ramus profundus) accompanied by the deep branch of the ulnar artery, passes between the Abductor digiti quinti and Flexor digiti quinti brevis; it then perforates the Opponens digiti quinti and follows the course of the deep volar arch beneath the Flexor tendons. At its origin it supplies the three short muscles of the little finger. As it crosses the deep part of the hand, it supplies all the Interossei and the third and fourth Lumbricales; it ends by supplying the Adductores pollicis and the medial head of the Flexor pollicis brevis. It also sends articular filaments to the wrist-joint.
It has been pointed out that the ulnar part of the Flexor digitorum profundus is supplied by the ulnar nerve; the third and fourth Lumbricales, which are connected with the tendons of this part of the muscle, are supplied by the same nerve. In like manner the lateral part of the Flexor digitorum profundus and the first and second Lumbricales are supplied by the median nerve; the third Lumbricalis frequently receives an additional twig from the median nerve.
The Radial Nerve (n. radialis; musculospiral nerve) (Fig. 818), the largest branch of the brachial plexus, is the continuation of the posterior cord of the plexus. Its fibres are derived from the fifth, sixth, seventh, and eighth cervical and first thoracic nerves. It descends behind the first part of the axillary artery and the upper part of the brachial artery, and in front of the tendons of the Latissimus dorsi and Teres major. It then winds around from the medial to the lateral side of the humerus in a groove with the a. profunda brachii, between the medial and lateral heads of the Triceps brachii. It pierces the lateral intermuscular septum, and passes between the Brachialis and Brachioradialis to the front of the lateral epicondyle, where it divides into a superficial and a deep branch.
The branches of the musculospiral nerve are:
The muscular branches (rami musculares) supply the Triceps brachii, Anconæus, Brachioradialis, Extensor carpi radialis longus, and Brachialis, and are grouped as medial, posterior, and lateral.
The medial muscular branches supply the medial and long heads of the Triceps brachii. That to the medial head is a long, slender filament, which lies close to the ulnar nerve as far as the lower third of the arm, and is therefore frequently spoken of as the ulnar collateral nerve.
The posterior muscular branch, of large size, arises from the nerve in the groove between the Triceps brachii and the humerus. It divides into filaments, which supply the medial and lateral heads of the Triceps brachii and the Anconæus muscles. The branch for the latter muscle is a long, slender filament, which descends in the substance of the medial head of the Triceps brachii.
The lateral muscular branches supply the Brachioradialis, Extensor carpi radialis longus, and the lateral part of the Brachialis.
The cutaneous branches are two in number, the posterior brachial cutaneous and the dorsal antibrachial cutaneous.
The posterior brachial cutaneous nerve (n. cutaneus brachii posterior; internal cutaneous branch of musculospiral) arises in the axilla, with the medial muscular branch. It is of small size, and passes through the axilla to the medial side of the area supplying the skin on its dorsal surface nearly as far as the olecranon. In its course it crosses behind, and communicates with, the intercostobrachial.