Nerves of Upper Limb

The nerve supply to the upper limb is provided by the brachial plexus. The five major nerves supplying the upper limb are:

• Axillary nerve.
• Musculocutaneous nerve.
• Radial nerve.
• Median nerve.
• Ulnar nerve.

The study of five major nerves of the upper limb should be studied thoroughly and carefully because of their frequent involvement in various injuries and peripheral neuropathy.

Axillary Nerve

The axillary nerve (C5 and C6) arises from posterior cord of brachial plexus. It provides motor sinnervation to the deltoid and teres minor muscles and sensory innervation to the shoulder joint and to the skin.

Type: Mixed sensory and motor nerve.

Origin: It emerges from the posterior cord of the brachial plexus(C5 and C6).

Course: It passes through the quadrangular space with the posterior circumflex humeral artery.

The axillary nerve (C5, C6) arises from the posterior cord of the brachial plexus near the lower border of the subscapularis. It passes backwards on subscapularis through the quadrangular space along with the posterior circumflex humeral artery runs. Thoroughly, here it is related to the medial aspect of the surgical neck of the humerus instantly inferior to the capsule of the shoulder joint. The nerve splits into branches accross the shoulder joint, and then works laterally to divide into the anterior and posterior branches, deep to deltoid.

Musculocutaneous Nerve

The musculocutaneous nerve appears from the lateral cord of the brachial plexus. It is the nerve of the front of arm. It operates downwards and laterally, pierces the coracobrachialis which it supplies, and then passes between the biceps and brachialis muscles. It is located at the lateral margin of the biceps tendon and just above the elbow it pierces the deep fascia and descends over the lateral part of the forearm as the lateral cutaneous nerve of the forearm.

Type: Mixed sensory and motor nerve.

Origin: It emerges from the lateral cord of the brachial plexus (C5, C6 and C7).

Course: Supplies the coracobrachialis and then passes between the biceps and brachialis muscle.

Radial Nerve

The radial nerve is a continuation of posterior cord of brachial plexus in the axilla. It is the largest nerve of the brachial plexus. It carries fibres from all the roots (C5, C6, C7, C8, and T1) of brachial plexus (but T1 fibres are not constant).

Type: Mixed sensory and motor nerve.

Origin: It emerges from all the roots of the brachial plexus (C5, C6, C7, C8, and T1)

In the axilla, the radial nerve lies posterior to the third part of the axillary artery and anterior to the muscles forming the posterior wall of the axilla.

In the axilla, it gives off the following three branches:

• Posterior cutaneous nerve of arm (which provides sensory innervation to skin on the back of the arm up to the elbow).
• Nerve to the long head of triceps.
• Nerve to the medial head of triceps.

Median Nerve

The Median Nerve is one of the five nerves that emerges from brachial plexus in axilla by two roots: (a) lateral and (b) medial.

The lateral root (C5, C6, and C7) emerges from lateral cord of brachial plexus and the medial root (C8 and T1) emerges from medial cord of the brachial plexus. The medial root crosses in front of the third part of axillary artery to connect with the lateral root in a Y-shaped manner possibly in front of or on the lateral side of the artery to compose the median nerve. So the root value of median nerve is C5, C6, C7, C8, and T1.

In the axilla, the median nerve is located on the lateral side of the third part of the axillary artery. It enters the arm at the lower border of teres major.

Ulnar Nerve

The Ulnar Nerve grows within the axilla from the medial cord of brachial plexus (C8 and T1). The ventral ramus of C7 contributes to the ulnar nerve. The C7 fibers in the ulnar nerve supply flexor carpi ulnaris.

In the axilla, the nerve lies medial to 3rd part of axillary artery (between axillary artery and vein).

Type: Mixed sensory and motor nerve.

Origin: It emerges from the medial part of the brachial plexus (C8 and T1).

Course: It runs distally along the medial side of the brachial artery as much as the midarm (level of insertion of coracobrachialis) and goes into the arm as part of primary neurovascular package.