Deltoid is constructed with three main sets of fibers:
Lateral/Medial (1)
Origin: Acromion Process (12)
Anterior (1a)
Origin: lateral third and anterior Surface of the Clavicle (11) 
Posterior (1b)
Origin: posterior border of the Scapula Spine (10)
Insertion: all fibers from three parts converge to insert to the Deltoid Tuberosity (13) on the Humerus
Actions: arm Abduction (all fibers), shoulder Flexion and Medial Rotation of the arm (anterior fibers), shoulder Extension and Lateral Rotation of the arm (posterior fibers)
Helping Synergist Muscles:
- together with Long Head of the Biceps Brachialis and Supraspinatus (2) acts to produce arm Abduction
- with Latissimus Dorsi, Teres Major (5), Long Head of the Triceps Brachii and Subscapularis acts to produce shoulder Extension
- together with Short Head of the Biceps Brachii, Pectoralis Major, Supraspinatus (2) and Infraspinatus acts to produce shoulder Flexion
Note: the Anterior part (1a) together with the Medial part (1), contribute to Anteversion. The Posterior part (1b)together with the Medial part (1), contribute to Retroversion