Serratus Posterior Muscles are- Serratus Posterior Superior Serratus Posterior Inferior Serratus Posterior Superior The serratus posterior superior is lying deep to the rhomboid muscles on the upper back. Attachments: Origin: The lower part of the ligamentum nuchae, and the cervical and thoracic spines (usually C7 – T3). Insertion: The fibers of the Serratus Posterior Superior pass in an inferolateral …