Brachial Plexus Segments

Brachial Plexus

Overview

The brachial plexus is a network of nerves in the shoulder that carries movement and sensory signals from the spinal cord to the arms and hands. It is composed of five named segments: Roots, Trunks, Divisions, Cords, and Terminal Branches.

Segments of the Brachial Plexus

1. Roots

• The roots are the anterior rami of spinal nerves C5, C6, C7, C8, and T1.

2. Trunks

• The roots merge to form three trunks:
  • Superior Trunk: Formed by the union of C5 and C6 roots.
  • Middle Trunk: Continuation of the C7 root.
  • Inferior Trunk: Formed by the union of C8 and T1 roots.

3. Divisions

• Each trunk divides into an anterior and a posterior division.

4. Cords

• The divisions converge to form three cords, named according to their position relative to the axillary artery:
  • Lateral Cord: Formed by the anterior divisions of the superior and middle trunks.
  • Posterior Cord: Formed by all three posterior divisions (from the superior, middle, and inferior trunks).
  • Medial Cord: Formed by the anterior division of the inferior trunk.

5. Terminal Branches (Nerves)

• The cords give rise to five major terminal branches (nerves):
  • Axillary Nerve
  • Musculocutaneous Nerve (MC)
  • Median Nerve
  • Ulnar Nerve
  • Radial Nerve

Mnemonic

• A common mnemonic to remember the order of the brachial plexus segments is: Roots Trunks Divisions Cords Branches (Randy Travis Drinks Cold Beer).