deltoids

The deltoid muscle is a large triangular shaped muscle occupying the upper arm and the shoulder giving it a rounded shape. It gets its name because of its similar shape to the Greek letter ‘delta’ (Δ).

Anatomically, the deltoid muscle appears to be made up of three distinct sets of muscle fibers, namely the:

anterior or clavicular part (pars clavicularis) <— front
posterior or scapular part (pars scapularis) <— rear
intermediate or acromial part (pars acromialis) <— sides

When all its fibers contract simultaneously, the deltoid is the prime mover of arm abduction along the frontal plane. The arm must be medially rotated for the deltoid to have maximum effect.

Deltoid muscles are a distinct feature in muscular builds.

If the deltoids are well developed and visible in a picture then it should be tagged.