*5.12.1 Extensor musculature*


primi longus (m. extensor pollicis longus): The origin is craniolaterally on the proximal half of the ulna and inserts into the distal phalanx of the pollex (**Figure 34**).

#### **Figure 32.**

*Lateral view of the musculature of the left forearm. A: superficial layer with 1: brachioradialis muscle, 2a: long part of extensor carpi radialis muscle, 2b: short part of extensor carpi radialis muscle, 3: extensor digitorum communis muscle, 4: extensor digitorum quarti et quinti muscle, 5: extensor carpi ulnaris muscle, 6: abductor digiti primi longus muscle. B: deep layer with 6: abductor digiti primi longus muscle, 7: extensor digitorum secundi et tertii muscle, 8: supinator muscle.*

#### **Figure 33.**

*Medial view of the musculature of the left forearm. A: Superficial layer with 1: m. flexor carpi ulnaris, 2: m. palmaris longus, 3: m. flexor carpi radialis, 4: m. flexor digitorum profundus, 5: m. pronator teres, 6: m. extensor carpi radialis longus, 7: m. brachioradialis. B: Deep layer with 4: m. flexor digitorum profundus, 6: m. extensor carpi radialis longus, 6*<sup>0</sup> *: m. extensor carpi radialis brevis, 7: m. brachioradialis, 8: m. flexor digitorum superficialis.*

secundi (m. extensor indicis) et tertii: This muscle arises distal to the former muscle. At the level of the carpus, the tendon splits into two tendons, one to the proximal phalanx of the 2nd digit and one for the 3rd digit (**Figures 32** and **34**).

quarti: From the lateral humeral epicondyle to proximal phalanx of the 4th digit (**Figures 32** and **34**).

quinti: From the lateral humeral epicondyle to the middle phalanx of the 5th digit (**Figures 32** and **34**).
