Musculocutaneous Nerve: The musculocutaneous nerve is responsible for bending/flexing our elbows. Tasks such as lifting a cup and brushing our teeth. The word musculocutaneous-‘Musculo’ implies its role in innervating muscles (motor part), and ‘cutaneous’ i.e. skin, suggests that has a sensory role.
Origin of the Musculocutaneous Nerve
The musculocutaneous nerve arises from the lateral cord of the brachial plexus at the inferior border of pectoralis minor muscle, its fibers being derived from C5, C6, and C7.
Course of the Musculocutaneous Nerve
- After arising from the brachial plexus, the nerve leaves the axilla and pierces the insertion of the coracobrachialis muscle on the humerus.
- It then passes down anterior to the brachialis muscle of the arm, but deep to the biceps brachii muscle, innervating them both muscles.
- The musculocutaneous nerve then emerges laterally to the biceps tendon and continues in the forearm as a lateral cutaneous nerve. It provides sensory innervation to the lateral aspect of the forearm.
Motor functions of the Musculocutaneous Nerve
- Anterior compartment of the arm – the biceps brachii, brachialis, and the
Coracobrachialis muscles(BBC).
Sensory functions of the Musculocutaneous Nerve
- Innervates skin on the lateral surface of the forearm.
Musculocutaneous Nerve Injuries
Relatively uncommon, the most common cause is a stab wound to the axilla region. Flexion at the shoulder is weakened. Elbow flexion is also affected, but can still be performed of the brachioradialis muscle. Also, supination is weakened but is also performed by the supinator muscle.
- Innervates skin on the lateral surface of the forearm.