MUSCLES AND NERVES
OF
ARM
LEARNING OBJECTIVES
• At the end of lecture student should:
–
–
–
–
–
–
Know the compartments of arm and how they are formed
Understand the muscles and their actions found in the arm
Know the nerve supply of arm
Know the course of the nerves
Know the branches of the nerves
Know the clinical correlations
MEDIAL INTERMUSCULAR SEPTUM
• It extends along the medial supracondylar line behind the
coracobrachialis insertion and fades out above b/w the muscle
and the long head of triceps
• It gives origin to most medial fibres of brachialis and the medial
head of triceps
• It is pierced by the ulnar nerve and the ulnar collateral artery.
LATERAL INTERMUSCULAR SEPTUM
• It extends along the medial supra-condylar line and fades out
behind the insertion of deltoid.
• Posteriorly the medial head of triceps arises from it
• It is pierced by the radial nerve and the profunda brachii artery.
POSTERIOR AND ANTERIOR COMPARTMENTS
ARM
A. Anterior arm muscles are Flexors of forearm/elbow joint
1. Biceps brachii
2. Brachialis
3. Coracobrachialis
B. Posterior arm muscles are Extensors of the forearm / elbow joint
1. Triceps brachii
BICEPS BRACHII
TRICEPS BRACHII
Extend Elbow Joint
Nerves of Arm
• Musculocutaneous nerve (Lateral cord)
– Nerve of anterior compartment of arm
• Radial nerve (Posterior cord)
– Nerve of posterior compartment of arm
• Other nerves are passing through the arm but they are not supplying the arm
– Median nerve)
– Ulnar nerve ) Medial cord
MUSCULOCUTANEOUS NERVE
• Main nerve that supply the front of arm.
• Branch of lateral cord of brachial plexus
• Root Value
– C5, C6, C7
MUSCULOCUTANEOUS NERVE
Course
In Axilla
– Arises from Lateral Cord
– Lies lateral to 3rd part of Axillary
Artery
Relation in Axilla
• Anteriorly
– Pectoralis Major
• Posteriorly
– Subscapularis
• Medially
– Axillary artery
– Lateral root of Median Nerve
• Laterally
– Coracobrachialis
• Leaves the axilla and enters front of arm by piercing the coracobrachialis.
MUSCULOCUTANEOUS NERVE
In Arm
• Runs downward and laterally between the biceps and brachialis
• Reaches lateral side of the tendon of the biceps piercing the deep fascia 2cm above
the bent of fore arm
• Continues as lateral cutaneous nerve of forearm.
MUSCULOCUTANEOUS NERVE
Branches
•
Muscular Branches
–
–
–
•
Cutaneous Branches
–
•
Coracobrachialis
Biceps
Brachialis
Through lateral cutaneous nerve of fore arm it supplies the skin of lateral side of fore arm from
elbow to wrist.
It also supplies elbow joint through its branch to brachialis.
RADIAL NERVE
• Main nerve that supplies the back of the arm
• It is largest branch of posterior cord of Brachial plexus.
• Root Value
– C5, C6, C7, C8, T1
RADIAL NERVE
Course
In Axilla
• Lies posterior to 3rd part of axillary artery.
• It rests on subcapularis, latissimus dorsi.
• Passes posteriorly with profunda brachii vessel through lower triangular space, below
teres major, between long head of triceps and humerus.
• Then enters the radial groove with profunda vessel.
RADIAL NERVE
In radial groove
• It runs downward and laterally between lateral and medial head of triceps.
• At the lower end of groove,5cm below the deltoid tuberosity the nerve pierces the
lateral intermuscular septum and passes into anterior compartment of arm.
RADIAL NERVE
Branches
In axilla
• Muscular branches
– 1.Long head of triceps
– 2.Medial head of triceps
•
Cutaneous branch
– 1.Posterior cutaneous nerve of arm.
In radial groove
• Muscular branches
– 1.Lateral head of triceps
– 2.Medial head of triceps
– 3.Anconeus
•
Cutaneous branches
– 1.Lower lateral cutaneous nerve of arm
– 2.Posterior cutaneous nerve of forearm
•
Articular branch
– To elbow joint
CLINICAL CORRELATES
Radial nerve is very commonly damaged in the region of radial groove
Cause of injury
• Intramuscular injection in triceps instead of deltoid
• Fracture of shaft of humerus
Clinical features
• Weakness or loss of power of extension at wrist (wrist drop)
• Sensory loss over back of lateral part of the dorsum of the hand
THANK YOU