Upper Limb

1. MUSCULOCUTANEOUS NERVE
Dr M Idris Siddiqui

2. Learning objectives
–The applied anatomy of the nerve.
–Its anatomical course,
–Motor functions.
–Cutaneous innervation.
–Clinicals.

3. MUSCULOCUTANEOUS NERVE
• It is the largest branch of lateral cord(C5, C6 and C7).
• It is the nerve of the front of arm.
• After supplyling 3 muscles, ends by becoming the
lateral cutaneous nerve of the forearm.
• It operates downwards and laterally, pierces the
coracobrachialis which it supplies, and then passes
between the biceps and brachialis muscles.
• It is located at the lateral margin of the biceps tendon
and just above the elbow it pierces the deep fascia and
descends over the lateral part of the forearm as
the lateral cutaneous nerve of the forearm.

6. MOTOR FUNCTIONS
• The musculocutaneous nerve innervates the
muscles in the anterior compartment of the
arm.
–Biceps brachii, brachialis and coracobrachialis.
• These muscles flex the upper arm at the
shoulder and the elbow.
• In addition, the biceps brachii also carries out
supination of the forearm.
• BBC.

9. SENSORY FUNCTIONS
• The musculocutaneous nerve gives rise to the
lateral cutaneous nerve of forearm.
• This nerve at first enters the deep forearm,
but then pierces the deep fascia to become
subcutaneous. In this region, it can be
discovered in close proximity to the cephalic
vein.
• The lateral cutaneous nerve of forearm
innervates the skin of the lateral aspect of the
forearm.

13. Clinical Relevance
Lesions of the Musculocutaneous Nerve
• How it commonly occurs: An injury to the
musculocutaneous nerve is relatively uncommon, as it
is well protected within the axilla. The most common
cause is a stab wound to the axilla region.
• Motor functions: The coracobrachialis, biceps brachii
and brachialis muscles are paralysed.
– Flexion at the shoulder is weakened, but can still occur due
to the pectoralis major.
– Flexion at the elbow is also affected, but can still be
performed because of the brachioradialis muscle.
– Also, supination of the affected limb is greatly weakened, but
still is produced by the supinator muscle.
• Sensory functions: Loss of sensation over the lateral
side of the forearm.

16. The axillary nerve
Dr M Idris Siddiqui

17. Learning objectives
– The applied anatomy of the axillary nerve
– Its anatomical course,
– Motor functions and
– Cutaneous innervation.
– The clinical correlations of damage to the axillary
nerve.

18. The axillary nerve
• The axillary nerve is one of the two
terminal branches of posterior cord of
the brachial plexus.
• Origin: it emerges from the posterior
cord of the brachial plexus.
• Course:it passes through the
quadrangular space in the axilla with the
posterior circumflex humeral artery.

19. The axillary nerve
• Type: mixed sensory and motor nerve.
• Spinal roots: C5 and C6.
• Motor functions: Innervates the teres minor
and deltoid muscles.
• Sensory functions: At last, it becomes
superior or upper lateral cutaneous nerve of
arm, which innervates the skin over the lower
deltoid regi e tal badge area .

25. Anatomical Course
• Immediately after its formation, the axillary
nerve lies posteriorly to the axillary
artery and anteriorly to the subscapularis
muscle.
• It descends to the inferior border of the
subscapularis muscle, and then exits the
axilla posteriorly via the quadrangular space.
• While turning around surgical neck of the
humerus, it is accompanied by the posterior
circumflex humeral artery.

28. The Quadrangular Space
• The quadrangular space is a gap in the muscles of
the posterior scapular region. It is a pathway for
neurovascular structures to move from the axilla to
the posterior shoulder and arm.
• Its boundaries are:
–Superior – Subscapularis and teres minor.
–Inferior – Teres major.
–Laterally – Surgical neck of humerus.
–Medially – Long head of triceps brachii.

29. BRANCHES
• In the posterior scapular region, the axillary
nerve terminates by dividing into two
branches:
1. Anterior terminal branch:
– It goes on horizontally between the deltoid and
surgical neck of the humerus with posterior
circumflex humeral vessels.
– Provides motor innervation to the deltoid
muscle.
2. Posterior terminal branch:

31. POSTERIOR BRANCH
• The posterior branch It proceeds over the posterior
border of the deltoid as upper lateral cutaneous
nerve of the arm and supplies the skin over the
lower half of the deltoid.
– After giving twig to to teres minor, curves around the
posterior border of the deltoid, it becomes the upper
lateral cutaneous nerve of the arm.
• The upper lateral cutaneous nerve is noted as a
sensory branch of the axillary nerve. It supplies the
skin over the lower part of deltoid and the upper
part of the long head of triceps.

32. Posterior branch
• The posterior branch is totally related to
the inferior aspects of the glenoid and
shoulder joint capsule.
–*here is often an enhancement or
pseudoganglion on the branch to teres
minor.
–The axillary trunk supplies a branch to the
shoulder joint below subscapularis.

33. Motor Functions
• The axillary nerve innervates the deltoid and
the teres minor muscles.
• The deltoid is innervated by the anterior terminal
branch of the axillary nerve.
– The deltoid performs abduction of the upper limb at the
glenohumeral joint.
• The teres minor is part of the rotator cuff muscles
of the shoulder.
– The muscle is innervated the posterior terminal
branch of the axillary nerve.

34. Sensory Functions
• The upper lateral cutaneous nerve of
the arm that arises from the posterior
terminal branch of the axillary nerve
innervates the skin over the inferior
portion of the deltoid (known as the
regimental badge area .
• In a patient with axillary nerve damage,
sensation at the regimental badge area
may be impaired i.e. paraesthesia.

36. Clinical Relevance
Injury to the Axillary Nerve
• The axillary nerve is most commonly damaged by
trauma to the shoulder or proximal humerus
– such as a fracture of the humerus surgical neck.
• Motor functions: Paralysis of the deltoid and teres
minor muscles. This renders the patient unable to
abduct the affected limb.
• Sensory functions: The upper lateral cutaneous nerve
of arm will be affected, resulting in loss of sensation
over the regimental badge area.
• Characteristic clinical signs: In long standing cases, the
paralysed deltoid muscle rapidly atrophies, and the
greater tuberosity can be palpated in that area.

39. Summary of the main branches of the axillary nerve