[TA] thoracoappendicular (scapulothoracic) muscle; origin, from center of lateral aspect of first eight to nine ribs; insertion, superior and inferior angles and intervening medial margin of scapula; action, rotates scapula and pulls it forward, elevates ribs; nerve supply, long thoracic from brachial plexus. SYN: musculus serratus anterior [TA], anterior serratus muscle, costoscapularis, musculus serratus magnus.