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Brachial plexus

The brachial plexus is an arrangement of nervous fibres (a plexus) running from the spine (vertebrae C5-T1), through the neck, the axilla (armpit region), and into the arm. All nerves of the arm stem from the brachial plexus (with the exception of the intercostobrachialis nerve which supplies an area of skin near the axilla). Therefore, lesions of the plexus can lead to severe functional impairment.

Diagram of the brachial plexus

The brachial plexus starts from the five ventral rami of the spinal nerves, these are the five roots. These roots merge to form three trunks.

Each trunk then splits to form an anterior and a posterior division. These six divisions will regroup to become the cords. The cords are named by their position in respect to the axillary artery.

From the cords come the nerves of the arm.