The radial artery then continues laterally in the forearm, eventually contributing to the superficial and deep palmar arches in the palmar aspect of the hand. Immediately superior to the antecubital fossa, the brachial artery branches into ulnar and radial arteries.
It then becomes the brachial artery once it passes the lower edge of the teres minor muscle. As it traverses towards the upper extremity, it becomes the axillary artery at the lateral border of the first rib. The subclavian artery branches off from the aortic arch. Below is a description of the extensor tendon zones: Įxtensor tendon zones are a helpful way to identify the region where injuries to the extensor tendons occur in the hand and wrist. Independent small finger extension is accomplished by the extensor digiti minimi (EDM) muscle. Independent index finger extension can be carried out by the extensor indicis proprius (EIP) muscle. When referencing the dorsal aspect of the wrist, the EPB and EPL tendons create the medial and lateral borders of the anatomic snuffbox, respectively.Įxtension of the second (index finger), third (long finger), fourth (ring finger), and fifth (small finger) digits occurs via the extensor digitorum communis (EDC) muscles. Thumb extension is carried out by abductor pollicis longus (APL), extensor pollicis brevis (EPB), and extensor pollicis longus (EPL).
Thus, in various clinical pathologies that may cause a dynamic imbalance between the radial-based extensors (ECRL and ECRB) versus the ulnar-based extensor (ECU), wrist extension will occur with simultaneous and involuntary radial/ulnar deviation. To achieve neutral wrist extension movements, the extensor carpi radialis brevis (ECRB), extensor carpi radialis longus (ECRL), and the extensor carpi ulnaris (ECU) muscles act synergistically based on each muscle's insertion and dynamic function.
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