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:
- Origin and root value.
- Branches and structures supplied.
- 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.
- It arises in the axilla from posterior cord of brachial plexus behind the third part of axillary artery.
- 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.
- 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.