Brachial Plexus

The brachial plexus and its branches provide the innervation of the upper limb. The brachial plexus is formed by merging of the anterior roots of C5-C8 spinal nerves and a large part of the anterior root of T1 spinal nerve.  In the neck, it is located in the interscalene space (between the anterior and middle scalene muscles). 

There are six divisions that arise from the three trunks - three anterior divisions (one for each trunk) and three posterior divisions (one for each trunk). The divisions then merge, forming the cords. Each trunk consists of an anterior and posterior part. A posterior cord is formed by the merging of posterior parts of all three trunks, lateral cord - from superior and medial trunk, medial cord - from the inferior trunk.

Topographically, the brachial plexus can be divided in two parts:

  • Above the clavicula - the supraclavicular part
  • Below - the infraclavicular part

Supraclavicular part of the brachial plexus

The supraclavicular part of the brachial plexus is located in the lateral triangle of the neck (trigonum colli laterale).

Branches from the supraclavicular part innervate the superficial layer of chest muscles, first and second layer of the superficial back muscles, muscles of the shoulder region (except the deltoid and teres minor).

7 nerves branch off the supraclavicular part of the brachial plexus:

  1. Dorsal scapular nerve
  2. Long thoracic nerve
  3. Suprascapular nerve
  4. Subclavian nerve
  5. Medial and lateral pectoral nerves
  6. Subscapular nerves
  7. Thoracodorsal nerve

Infraclavicular part of the brachial plexus

The infraclavicular part of the brachial plexus is formed by the three fascicles that surround the axillary artery.

  • The lateral fascicle is formed by the anterior parts of the superior and middle trunks. The lateral fascicle is the origin of the musculocutaneous nerve and the lateral root of the median nerve.
  • The medial fascicle branches and forms the medial brachial cutaneous nerve, medial antebrachial cutaneous nerve and the ulnar nerve.
  • The posterior fascicle forms two nerves - the radial nerve and the axillary nerve.