Summary Serratus Origin Superolateral surfaces of upper 8 or 9 ribs at the side of chest Insertion Vertebral border of scapula Action Draws scapula forward and upward; abducts scapula and rotates it; stabilizes vertebral border of scapula Innervation Long thoracic nerve (C5, C6, C7) Arterial Supply Circumflex scapular artery Clinical Conditions Medial scapular Winging