With the biceps brachii muscle reflected laterally, study the course of the musculocutaneous nerve through the arm. First, identify the coracobrachialis muscle [probe]. It serves as a key landmark because the musculocutaneous nerve passes through this muscle as it leaves the axilla and enters the arm.
The musculocutaneous nerve [probe indicates branch to biceps brachii muscle] arises as a terminal branch of the lateral cord of the brachial plexus [ upper probe], pierces the coracobrachialis muscle, and passes distally between the biceps brachii muscle and brachialis muscle. This nerve provides motor innervation to the coracobrachialis muscle, biceps brachii muscle [branches lower probe], and brachialis muscle. Distally, its terminal cutaneous branch, called the lateral antebrachial cutaneous nerve [probe], passes lateral to the tendon of the biceps muscle and enters the forearm, providing cutaneous sensation to that region.
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