Anatomy of Brachial Plexus

Brachial Plexus

• A major nerve network that begins in the neck and extends into the axilla, supplying the upper limb with motor, sensory, and autonomic innervation.

Formation

• Formed by the union of the anterior rami of the last four cervical and the first thoracic spinal nerves that constitute the roots.
• Roots usually pass through the gap between the anterior and middle scalene muscles with the subclavian artery.
• In the inferior part of the neck, the roots unite to form three trunks: superior, middle, and inferior trunks.
• Superior trunk formed by the union of C5 and C6 roots.
• Middle trunk is a continuation of the C7 root.
• Inferior trunk formed by the union of C8 and T1 roots.

Divisions and Cords

• Each trunk divides into anterior and posterior divisions as the plexus passes through the cervicoaxillary canal posterior to the clavicle.
• Anterior divisions of the superior and middle trunks unite to form the lateral cord.
• Anterior division of the inferior trunk continues as the medial cord.
• Posterior divisions of all three trunks unite to form the posterior cord.

Branches of Brachial Plexus

• Branches from the roots:
  • Dorsal Scapular Nerve (C5): innervates rhomboids and levator scapulae.
  • Long Thoracic Nerve (C5,6,7): innervates serratus anterior.
• Branches from the trunks (Superior only):
  • Suprascapular Nerve (C5,6): innervates supra and infraspinatus.
  • Nerve to Subclavius (C5,6).
• Branches from Lateral Cord:
  • Lateral Pectoral Nerve (C5,6,7): innervates pectoralis major.
  • Musculocutaneous Nerve (C5,6,7): innervates biceps brachii and coracobrachialis.
  • Lateral root of Median Nerve (C5,6,7).
• Branches from Medial Cord:
  • Medial Pectoral Nerve.