Neurovasculature of upper limb
The upper limb structures are supplied by complex networks of arteries, veins and nerves. Below, we will list the main arteries supplying oxygenated blood to the tissues of the upper limb; the veins which drain deoxygenated blood; and the nerves responsible for conducting nerve impulses in this area of the body.
The upper limb’s main arterial supply begins from the chest as the subclavian artery, which is derived from the aortic arch and its first branch, the brachiocephalic artery. It gives off several branches that supply the head, neck, chest, and scapular regions, before it becomes the axillary artery at the level of the first rib.
The axillary artery is an important large blood vessel that supplies the shoulder and scapula. At the lower border of the teres major muscle, it continues as the brachial artery.
The brachial artery travels medially along the posterior surface of the humerus and terminates at the level of the elbow, where it bifurcates into radial and ulnar arteries. These branches extend to the forearm and wrist, giving rise to recurrent, muscular and cutaneous branches. The ulnar artery further subdivides into anterior and posterior interosseous arteries. Variable radial and ulnar arteries anastomose in the palmar aspect of the hand to supply the thumb and the rest of the digits.
The venous supply of the upper limb drains deoxygenated blood from the shoulder, arm, forearm and hand. It consists of both superficial and deep veins. The main superficial veins of the upper limb are the cephalic and basilic veins. They arise from the dorsal venous network in the subcutaneous tissue on the dorsum of the hand.
The medial cubital vein connects between the cephalic and basilic veins at the level of the elbow. Deep veins lie internal to the deep fascia and accompany the major arteries of the upper limb. Unlike the superficial veins, they occur in pairs. Perforating veins run between the superficial and deep veins, and form a communication between them.
The brachial plexus is a major network of nerve fibers that almost supplies the entirety of the upper limb. It begins in the neck and extends to the axilla, where most of the branches arise. The brachial plexus is formed by the anterior rami of the last four cervical spinal nerves C5, C6, C7 and C8, and the first thoracic spinal nerve T1. The brachial plexus is divided into roots, trunks, divisions, cords, and branches.
The musculocutaneous nerve (C5, C6, and C7) arises from the lateral cord and supplies the coracobrachialis, brachialis, and biceps brachii muscles. The median nerve (C6 – T1) has roots arising from both lateral and medial cords, both of which supply various muscles including flexors of the arm and hand muscles.
The medial cord gives rise to the root of the median nerve as mentioned before, and the ulnar nerve. The ulnar nerve (C8, T1) runs intimately and superficially along the ulnar bone, and is the largest unprotected nerve of the body. It innervates the flexor carpi ulnaris, flexor digitorum profundus as well as several other muscles of the hand.
The posterior cord branches include the subscapular nerve, axillary nerve, and radial nerve. The subscapular nerve (C5, C6) supplies the lower aspect of the subscapularis and teres major muscles, while the axillary nerve (C5, C6) supplies the deltoid and teres minor muscles. The radial nerve (C5-C8 and T1) supplies the triceps brachii, and other muscles responsible for the extension of the wrists and digits, and supination of the forearm.