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Brachial Plexus Anatomy

 Brachial Plexus Anatomy

The brachial plexus Anatomy is a complicated network of nerves arises from the anterior rami of the cervical spine roots of (C5 – C6 – C7 – C8 – T1). The brachial plexus begins to form distal to the scalene muscle.

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.

Brachial Plexus palsy can be seen in infant after birth or in adult patient after trauma or accidents.

See Also: Brachial Plexus Palsy
muscles around Brachial Plexus
Muscles around Brachial Plexus

Parts of Brachial Plexus:

The Brachial Plexus consists of ( 5 Roots – 3 Trunks – 6 Divisions – 3 Cords – 5 Terminal Branches) respectively :

brachial plexus nerves
Brachial Plexus Parts

The only nerves that arise from the Brachial Plexus root directly are:

Dorsal scapular nerve:

nerves of Brachial Plexus

The Long Thoracic nerve:

Its long and relatively superficial course makes it susceptible to injury from any of the following causes:

The most common cause of long thoracic nerve injury results from carrying a heavy object on the shoulder. Other causes include:

  1. postinfection,
  2. postinjection,
  3. postpartum,
  4. postoperative.

The typical clinical presentation includes the following:

  1. Vague pain in the neck and the scapula region
  2. An inability to fully elevate the arm overhead
  3. Shoulder flexion and abduction are weak and limited in AROM due to the loss of the trapezius–serratus anterior force couple.
  4. The clinician should note winging of the scapula when testing the serratus anterior.
The Long Thoracic nerve
The Long Thoracic nerve

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 subclavius muscle acts mainly on the stability of the sternoclavicular joint, with more or less intensity, according to the degree of the clavicular interaction with the movements of the peripheral parts of the superior limb, and seems to act as a substitute for the ligaments of the sternoclavicular joint.

The Divisions:

Each trunk is divided into two divisions:

  1. Anterior Division.
  2. 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:

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): supplies the subscapularis muscle
  2. Thoracodorsal (Middle Subscapular) Nerve (C6 – C7 – C8): This nerve courses along the posterior–lateral chest wall, along the surface of the serratus anterior, and deep to the subscapularis, giving rise to branches that supply the latissimus dorsi.
  3. Lower Subscapular Nerve (C5 – C6): supplies the teres major and part of the subscapularis muscle.

The Medial Cord is formed by the anterior division of the lower trunk alone, it gives arise to the (Respectively from proximal to distal):

These cords is named based on their relationship with the axillary artery:

Brachial Plexus cords and axillary nerve
Brachial Plexus cords and axillary nerve

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

The medial and lateral pectoral nerves supply the pectoralis major (it has dual innervation) and pectoralis minor muscles.

The lateral pectoral nerve (C5–7) is actually more medial in the muscle, travels with the thoracoacromial vessels, and innervates the clavicular and sternal heads.

The medial pectoral nerve (C8–T1) shares a course with the lateral thoracic vessels and provides innervation to the sternal and costal heads. The main trunk of these nerves can be found near the origin of the vascular supply of the muscle.

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.


  1. Polcaro L, Charlick M, Daly DT. Anatomy, Head and Neck, Brachial Plexus. [Updated 2021 Aug 11]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK531473/
  2. Dutton’s Orthopaedic Examination, Evaluation, And Intervention 3rd Edition.
  3. Millers Review of Orthopaedics -7th Edition Book.
  4. Campbel’s Operative Orthopaedics 12th edition Book.

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