Anterior - shoulder flexion, inward rotation and horizontally adducts.
Middle - abduction.
Posterior - extention, horizontal abduction and outward rotation.
Deltoid - Anterior, Middle & Posterior portions
Origin
Anterior - Outer third of the clavicle
Middle - Top of the acromion process
Posterior - Spine of the scapula
Insertion
Anterior, Middle & Posterior - Lateral aspect of the humerus at the midpoint.
Action = The muscle as a whole abducts the humerus at the glenohumeral joint (GH joint).
Anterior - shoulder flexion, inward rotation and horizontally adducts.
Middle - abduction.
Posterior - extention, horizontal abduction and outward rotation.