Which nerve innervates the clavicular head of the pectoralis major?

The clavicular head of the pectoralis major is primarily innervated by the lateral pectoral nerve. This nerve provides motor innervation to the upper portion of the pectoralis major, which is crucial for movements involving shoulder flexion and adduction. The lateral pectoral nerve arises from the lateral cord of the brachial plexus, specifically from the C5-C7 spinal nerves, which aligns perfectly with the muscle’s origin and function.

In the context of the other options, while the medial pectoral nerve innervates the sternal head of the pectoralis major and the pectoralis minor, it does not supply the clavicular head. The upper subscapular nerve primarily innervates the subscapularis muscle, and the thoracodorsal nerve innervates the latissimus dorsi, neither of which are involved with the pectoralis major. Thus, the lateral pectoral nerve's role is crucial for the specific innervation of the clavicular head of the pectoralis major.