Brachial plexus

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The right brachial plexus with its short branches, viewed from in front.

The brachial plexus is a group of nerves. It runs from the vertebral column to the arm.

Structure[change | change source]

The brachial plexus is divided into five roots, three trunks, six divisions, three cords, and five branches.

Roots[change | change source]

The five roots come out of the spinal cord. They are each named after the part of the spinal cord they come out of: C5, C6, C7, C8, and T1.

Trunks[change | change source]

These roots join to form three trunks:

  • "upper" (C5-C6)
  • "middle" (C7)
  • "lower" (C8-T1)

Divisions[change | change source]

Each trunk then splits into two divisions:

  • anterior (front) divisions of the upper, middle, and lower trunks
  • posterior (back) divisions of the upper, middle, and lower trunks

Cords[change | change source]

These six divisions join up again to become the three cords.

  • The posterior cord is formed from the three posterior divisions of the trunks (C5-C8,T1)
  • The lateral cord is formed from the anterior divisions of the upper and middle trunks (C5-C7)
  • The medial cord is simply a continuation of the anterior division of the lower trunk (C8,T1)

Diagram[change | change source]

Drawing of the brachial plexus using colour to show where all the different nerves come from
The brachial plexus

Nerves[change | change source]

The nerves that come out of the brachial plexus include:

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