What is the muscle responsible for shoulder abduction and its spinal root innervation?

The deltoid muscle is primarily responsible for shoulder abduction, with its major action being to lift the arm away from the body. The deltoid has three distinct parts—anterior, middle, and posterior—that work together to facilitate this movement. The spinal root innervation for the deltoid muscle comes from the C5 and C6 spinal nerves. These nerve roots are part of the brachial plexus, which supplies motor function and sensation to the upper limbs.

The C5 and C6 boundaries are significant as they provide muscle strength and control necessary for various activities involving shoulder and arm movement, such as lifting, reaching, and throwing. Recognizing the innervation is crucial for understanding potential nerve injuries or complications that may affect the shoulder's function, frequently assessed in physical therapy and clinical settings.

The other options do not accurately reflect the anatomy related to shoulder abduction and its appropriate spinal innervation.