Scapula:A flat, triangular bone located on each side of the upper back that forms part of the shoulder girdle and provides attachment sites for muscles.
Medial border of scapula: The edge of the scapula closest to the vertebral column, running vertically and contributing to articulation and muscle attachment.
Acromion:An extension of the scapular spine that forms the highest point of the shoulder and articulates with the clavicle to form part of the acromioclavicular joint