Infraclavicular part of brachial plexus

The infraclavicular part of brachial plexus lies distal to the clavicle and includes the cords and their branches. The cords—lateral, medial, and posterior—are named based on their positional relationship to the axillary artery and are formed from the anterior and posterior divisions of the brachial plexus trunks:

• Lateral cord: Formed by the anterior divisions of the superior and middle trunks.

• Medial cord: Formed by the anterior division of the inferior trunk.

• Posterior cord: Formed by the posterior divisions of the superior, middle, and inferior trunks.

The cords give rise to two types of branches: non-terminal branches, which supply proximal muscles or provide sensory innervation, and terminal branches, which supply the upper limb.

Non-Terminal Branches of the Cords of the Brachial Plexus

The non-terminal branches are smaller nerves that arise from the cords to supply specific muscles or skin areas.

1. From the lateral cord:

• Lateral pectoral nerve (C5, C6, C7): Innervates the pectoralis major muscle.

2. From the medial cord:

• Medial pectoral nerve (C8, T1): Innervates both the pectoralis major and pectoralis minor muscles.

• Medial cutaneous nerve of arm (C8, T1): Provides sensory innervation to the skin of the medial arm.

• Medial cutaneous nerve of forearm (C8, T1): Provides sensory innervation to the skin of the medial forearm.

3. From the posterior cord:

• Upper subscapular nerve (C5, C6): Innervates the subscapularis muscle.

• Lower subscapular nerve (C5, C6): Innervates both the subscapularis and teres major muscles.

• Thoracodorsal nerve (C6, C7, C8): Innervates the latissimus dorsi muscle.

Terminal Branches of the Brachial Plexus

The terminal branches are the five main nerves of the upper limb, arising distally from the cords:

• Musculocutaneous nerve (C5-C7): Originates from the lateral cord and supplies the flexor muscles of the anterior compartment of the arm.

• Axillary nerve (C5, C6): Originates from the posterior cord; it innervates the deltoid and teres minor muscles.

• Radial nerve (C5-T1): Also from the posterior cord, it supplies the extensor muscles of the arm and forearm.

• Median nerve (C6-T1): Formed by contributions from the lateral and medial cords, it provides motor and sensory innervation to much of the flexor side of the forearm and hand.

• Ulnar nerve (C8, T1): Arises solely from the medial cord and innervates intrinsic hand muscles and parts of the flexor forearm.