What is the innervation of the anterior scalene muscle?

The anterior scalene muscle is primarily innervated by the ventral rami of the lower cervical nerves, specifically C4 to C6. This nerve supply allows the anterior scalene to function effectively in its roles, which include elevating the first rib and assisting in lateral flexion of the neck. The specific innervation means that these spinal nerves branch off and provide the necessary motor signals that enable the muscle to contract and perform its physiological roles. This anatomical detail is significant for understanding how the anterior scalene interacts with other neck and respiratory muscles during movement and breathing.

The options that refer to other spinal nerve levels, cranial nerves, or unrelated plexus branches are not applicable, as they do not correspond to the direct innervation of the anterior scalene muscle.