Axillary Nerve

Learning Objectives

After reading this post you will know:

  • Origin and root value of axillary nerve.
  • Course of axillary nerve.
  • Branches and structures supplied by axillary nerve.
  • Effects of lesion of axillary nerve.

Q. Describe the axillary nerve  under the following headings:

  1. Origin and root value.
  2. Course
  3. Branches and structures supplied.
  4. Applied aspect.

 A. Axillary nerve

  • Origin and root value : Axillary nerve is a branch of posterior cord of brachial plexus. Its root value is C5,C6 segments of spinal cord.
  • Course:
    • It arises in the axilla from posterior cord of brachial plexus behind the third part of axillary artery.axillary nerve
    • Then it runs backwards in close relation to the capsule of shoulder joint .
    • Enters  and  passes backwards through the quadrangular space.
    • It  terminates by dividing into anterior and posterior divisions.
    • Anterior branch accompanies the posterior circumflex humeral vessels  and winds around the surgical neck of humerus, deep to deltoid.
    • Posterior branch pierces deep fascia along the posterior border of lower part of deltoid and continues as upper lateral cutaneous nerve of arm.
  • Branches and distribution:
    •  Branch to capsule of shoulder joint
    • Anterior branch supplies:
      • Deltoid muscle
      • Skin over anteroinferior part of deltoid muscle.
    • Posterior branch supplies:
      •   Teres minor and deltoid muscle ( the branch to teres minor bears pseudoganglion)
      • It continues as upper lateral cutaneous nerve of the arm which supplies the skin over the lower half of deltoid.

axillary nerve branches

  • Applied Anatomy:
  • The axillary nerve may get injured due to :
    • Inferior dislocation of head of humerus
    • Fracture of surgical neck of humerus
    • Improper use of crutches.
  • The injury to axillary nerve results in :
    • Impaired abduction of shoulder joint due to paralysis of deltoid muscle.
    • Loss of rounded contour of shoulder due to flaccid paralysis of deltoid muscle.
    • Loss of sensation over the lower half of the deltoid.
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