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Structure

Brachial plexus

Not medically reviewed · Content last updated · 2 min read ·

This is the date the draft was written, not a medical review date.

The brachial plexus is the network of nerves formed by the ventral rami of C5-T1 that supplies the upper limb and shoulder girdle. Its organisation (roots, trunks, divisions, cords, branches) allows localisation of injuries.

Terminologia Anatomica (Latin): Plexus brachialis · Open in the 3D atlas

Location

Begins in the posterior triangle of the neck between scalenus anterior and medius, passes over the first rib behind the clavicle, and enters the axilla around the axillary artery.

Structure

Five roots (C5-T1) form three trunks (upper C5-C6, middle C7, lower C8-T1); each trunk splits into anterior and posterior divisions, which form the lateral, posterior and medial cords (named from the axillary artery). Terminal branches: musculocutaneous, axillary, radial, median and ulnar nerves.

Blood supply

The plexus is accompanied by the subclavian and axillary arteries, with small vasa nervorum from adjacent branches (for example the ascending cervical, transverse cervical and subscapular arteries).

Innervation

Branches before the cords include the dorsal scapular (C5), long thoracic (C5-C7, serratus anterior), suprascapular (C5-C6) and nerve to subclavius. Cord branches include lateral pectoral, upper and lower subscapular, thoracodorsal, medial pectoral, and medial cutaneous nerves of arm and forearm. The terminal nerves supply all upper limb muscles and skin.

Function

It provides all motor and cutaneous sensory innervation of the upper limb (apart from the trapezius and a small area of the upper arm and axilla), and carries sympathetic fibres to the limb.

Clinical correlations

Erb palsy (upper trunk, C5-C6; for example birth injury or traction) gives the waiter’s-tip posture with shoulder adduction and internal rotation, elbow extension and forearm pronation. Klumpke palsy (lower trunk, C8-T1) causes claw hand and may give Horner syndrome. Other lesions: long thoracic nerve (winged scapula), axillary nerve (shoulder dislocation) and thoracic outlet syndrome.

Common exam points

  • Roots C5-T1, trunks (upper, middle, lower), divisions, cords (lateral, posterior, medial), branches: remember RTDCB.
  • Erb palsy: upper trunk C5-C6; waiter’s-tip posture.
  • Klumpke palsy: lower trunk C8-T1; claw hand, possible Horner syndrome.
  • Long thoracic nerve (C5-C7) injury: winged scapula (serratus anterior).
  • Axillary nerve and surgical neck of humerus: deltoid weakness, sensory loss over regimental badge area.

References

  1. Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
  2. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. Wolters Kluwer, 8th edition (2018) — Tier 3 (textbook)
  3. Netter FH. Atlas of Human Anatomy. Elsevier — Tier 3 (textbook)

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