Anatomy

Question 1

Peripheral Nerves: Upper Limb

Axillary Nerve

1. Nerve roots / cord
2. Innervates ?

Answer 1

1. C5, C6 / POSTERIOR CORD [Terminal branch of posterior cord]
2. Innervates

[i] Posterior branch (minor branch)
innervates the POSTERIOR DELTOID & TERES MINOR before terminating as the SUPERIOR LATERAL CUTANEOUS NERVE OF THE ARM

[ii] Anterior branch (major branch)
runs around the SURGICAL NECK OF HUMERUS from posterior to anterior deep to the deltoid muscle 5-7CM BELOW the ACROMION, supplying the MIDDLE & ANTERIOR DELTOID, as well as a patch of skin (REGIMENTS BADGE) before terminating

Question 2

Peripheral Nerves: Upper Limb

Axillary Nerve

1. Course

Answer 2

1. Runs along the INFERIOR BORDER of SUBSCAPULARIS 3-5mm from its musculotendinous junction
2. Runs through the QUADRANGULAR SPACE along with the POSTERIOR CIRCUMFLEX HUMERAL ARTERY
   [At this point, the nerve lies intimate with the INFERIOR JOINT CAPSULE]
3. The nerve runs POSTERIOR to HUMERUS and divides into the ANTERIOR & POSTERIOR BRANCHES
   3a. Posterior branch (minor branch) innervates the POSTERIOR DELTOID & TERES MINOR before terminating as the SUPERIOR LATERAL CUTANEOUS NERVE OF THE ARM
   3b. Anterior branch (major branch) runs around the SURGICAL NECK OF HUMERUS from posterior to anterior deep to the deltoid muscle 5-7CM BELOW the ACROMION, supplying the MIDDLE & ANTERIOR DELTOID, as well as a patch of skin (REGIMENTS BADGE) before terminating