The deltoid muscle is a large, triangular muscle covering the shoulder joint. Its shape resembles the Greek letter delta (Δ), hence its name. It's responsible for the rounded contour of the shoulder.
Anatomy and Function
The deltoid muscle is a powerful muscle with three distinct parts:
- Anterior (front) fibers: These fibers help flex (raise) and internally rotate the arm.
- Middle (lateral) fibers: These fibers primarily abduct (raise the arm out to the side) the arm.
- Posterior (rear) fibers: These fibers help extend (lower or move back) and externally rotate the arm.
The deltoid's location and function make it crucial for a wide range of arm movements, from lifting objects to throwing a ball. Its thick and spread-out nature provides significant strength and stability to the shoulder joint. As noted in the provided reference, its "shape resembles the inverted Greek letter delta." This description highlights its distinctive triangular form. The image referenced (though not provided here) would further illustrate its surface anatomy and positioning.
