• The brachial plexus arises from the anterior rami of the cervical spine roots of (C5 – C6 – C7 – C8 – T1).
    • Sometimes C5 receives some fibers from C4 and T1 also receives some fibers from T2.
  • Shortly after leaving the intervertebral foramen, each root receives its sympathetic component via a gray ramus.
  • The cervical roots receive their sympathetic components from one of the lower cervical sympathetic ganglia and the T1 root from its own sympathetic ganglion after contributing a white ramus to it.
  • The brachial plexus begins to form distal to the scalene muscle.
  • Brachial Plexus palsy can be seen in infant after birth or in adult patient after trauma or accidents.

Parts of Brachial Plexus:

  • The Brachial Plexus consists of ( 5 Roots – 3 Trunks – 6 Divisions – 3 Cords – 5 Terminal Branches) respectively :
    • Roots are the anterior rami of (C5 – C6 – C7 – C8 – T1) as mentioned above.
    • Trunks are ( Upper – Middle – Lower trunk).
    • Divisions are anterior and posterior of each trunks.
    • Cords are ( Lateral – Posterior – Medial)
  • The only nerves that arise from the root directly are:
    • Dorsal scapular nerve: arises from C5 root, it’s the first important branch seen when the plexus is explored superior to the clavicle.
    • The Long Thoracic nerve arises from C5 – C6 – C7 cervical roots.

The Trunks:

  • There are three trunks formed from the united of the roots.
  • They proceed infero-laterally behind the clavicle:
  • The three trunks are:
    1. The Upper trunk is formed by the united of C5 & C6 cervical roots.
    2. The Middle trunks is formed by the C7 cervical root alone.
    3. The Lower trunk is formed by the united of the C8 & T1.
  • The upper trunk gives arise to:
    1. Suprascapular nerve.
    2. Subclavius nerve.

The Divisions:

  • Each trunk is divided into two divisions:
    • Anterior Division.
    • Posterior Division.
  • No Nerves arise from the divisions.

The Cords:

  • The Lateral Cord is formed by the united of the anterior divisions of the upper and middle trunks, it gives arise to the:
    1. Lateral Pectoral Nerve (C5 – C6 – C7).
  • The Posterior Cord is formed by the united of the three posterior divisions, , it gives arise to the (Respectively from proximal to distal):
    1. Upper Subscapular Nerve (C5 – C6)
    2. Thoracodorsal (Middle Subscapular) Nerve (C6 – C7 – C8).
    3. Lower Subscapular Nerve (C5 – C6).
  • The Medial Cord is formed by the anterior division of the lower trunk alone, it gives arise to the (Respectively from proximal to distal):
    1. Medial Pectoral Nerve (C5 – C6 – C7).
    2. Medial Brachial Cutaneous Nerve (T1).
    3. Medial Antebrachial Cutaneous Nerve (C8 – T1).
  • These cords is named based on their relationship with the axillary artery:
    1. Lateral Cord is located lateral to the axillary artery.
    2. Posterior Cord is located posterior to the axillary artery.
    3. Medial Cord is located medial to the axillary artery.

Notice: The lateral pectoral nerve and the medial pectoral nerve communicate by an anastomotic loop.

Terminal Branches:

  1. The Musculocutaneous Nerve (C5 – C6 – C7): arises from the lateral cord.
  2. The Axillary Nerve (C5 – C6): arises from the posterior cord.
  3. The Radial Nerve (C5 – C6 – C7 – C8 – T1): arises from the posterior cord.
  4. The Median Nerve (C5 – C6 – C7 – C8 – T1): arises from the lateral & medial cord.
  5. The Ulnar Nerve (C7 – C8 – T1): arises from the medial cord.