Brachial plexus: Anatomy

Basic, Basic Sciences

  • The brachial plexus is formed by the union of the anterior primary divisions of the 5th-8th cervical nerves and the 1st thoracic nerve

  • As the nerve roots leave the intervertebral foramina they converge, successively forming trunks -> divisions -> cords -> branches -> terminal nerves

  • * Mnemonic for order: Randy Travis Drinks Cold Beer (Roots > trunks > cords > branches)

  • Trunks:

  • 3 trunks: superior, middle, and inferior

  • Located between the anterior and middle scalene muscles

  • Divisions:

  • Formed as the trunks pass over the lateral border of the 1st rib and under the clavicle

  • Each of the 3 trunks divides into anterior and posterior divisions

  • Cords:

  • Formed as the brachial plexus emerges below the clavicle and the fibers of the divisions combine again to form 3 cords

  • Named according to their relationship to the axial artery: lateral, medial, and posterior

  • At the lateral border of the pectoralis minor muscle, each cord gives off a major branch before ending as a terminal nerve

  • Terminal Nerves

  • Lateral cord gives off the lateral branch of the median nerve and ends as the musculocutaneous nerve

  • Medial cord gives off the medial branch of the median nerve and ends as the ulnar nerve

  • Posterior cord gives of the axillary nerve and terminates as the radial nerve


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Answered correctly


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Kelsey Savery, MD