Final answer:
The upper subscapular nerve is innervated by spinal nerves C5 and C6, which are part of the posterior cord of the brachial plexus and contribute to movements in the shoulder and arm.
Step-by-step explanation:
The upper subscapular nerve is innervated by C5 and C6.
The upper subscapular nerve is a branch of the posterior cord of the brachial plexus, which is associated with the lower cervical spinal nerves and the first thoracic spinal nerve. The brachial plexus is formed by the union of spinal nerves C5 to C8 and T1, and it innervates the upper limb. The upper subscapular nerve specifically arises from the posterior cord, which receives contributions from the C5 and C6 nerve roots, and therefore, C5 and C6 are involved in the innervation of this nerve.
It is important for the student to understand that this specific innervation plays a role in shoulder and arm movements, and knowledge of nerve roots is essential for diagnosing nerve damage or injury.