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Musculocutaneous nerve

Anatomy and areas supplied by the musculocutaneous nerve.

The musculocutaneous nerve is responsible for very important function we use every day, bending/flexing our elbows. Tasks such as lifting a cup and brushing our teeth can become very difficult if the nerve is not functioning well.

The word musculocutaneous gives us a clue as to what the nerve does. ‘Musculo’ implies its role in innervating muscles (motor part), and ‘cutaneous’ i.e. skin, suggests that it also has a sensory role. This article will discuss the basic anatomy of the nerve, as well as its functional purpose and clinical relevance.

Key facts about the musculocutaneous nerve
Origin Brachial plexus (C5-C7)
Supply area Coracobrachialis, biceps brachii and brachialis muscles
Clinical relations Brachial plexus injury
Contents
  1. Origin
  2. Course and innervation
  3. Clinical notes
    1. Brachial plexus injury
    2. Stab wound and clinical consequences
    3. Variation
  4. Sources
+ Show all

Origin

The musculocutaneous nerve originates from the lateral cord of the brachial plexus (C5-C7) at the inferior border of pectoralis minor muscle. The brachial plexus itself originates from the anterior rami of the spinal nerves C5-T1. The roots emerge between the anterior and middle scalene muscles, and coalesce and mingle to form an upper, middle and lower trunk, which eventually give rise to a medial, lateral and posterior cord (all associated closely with and surrounding the axillary artery).

Not sure what the brachial plexus is? Learn the anatomy in half the time with our brachial plexus quizzes and labeling activities.

The cords are named according to their relation with the axillary artery. Locating the nerve whilst dissecting is simply a case of identifying coracobrachialis, and looking for the nerve entering it.

Brachial plexus in a cadaver. Notice musculocutaneous nerve originating from the lateral cord of the plexus.

Learn more about the brachial plexus here:

Course and innervation

The musculocutaneous nerve emerges as the terminal branch of the lateral cord of the brachial plexus, from the C5-C7 nerve roots. The first muscle it enters is coracobrachialis and gives branches to this muscle before entering it. From here it runs in the flexor compartment superficial to the brachialis but deep to the biceps brachii muscle. As it descends it innervates both of these muscles.

After giving small branch to the humerus and articular branches to the elbow joint it pierces deep fascia and emerges lateral to biceps brachii. It then continues as the lateral cutaneous nerve of the forearm.

The musculocutaneous nerve terminates as the lateral cutaneous nerve of the forearm that supplies the anterolateral skin of the forearm.

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