Final answer:
The dorsal scapular nerve innervates the rhomboid muscles, specifically the rhomboid major and rhomboid minor muscles. These muscles assist in retracting and elevating the scapula.
Step-by-step explanation:
The dorsal scapular nerve innervates the rhomboid muscles of the back. The rhomboid major and rhomboid minor muscles are located between the vertebral border of the scapula and the spinous processes of the thoracic vertebrae. They are responsible for retracting and elevating the scapula, helping to bring the shoulder blades closer to the spine.