Ace Netter's Anatomy 2026 – Dive into the World of Medicine and Master the Human Body!

In muscle morphology, shape terms describe how a muscle looks. A four-sided muscle is described as quadrate because the word means four-sided or square in form. This name fits muscles that appear boxy or rectangular in outline, such as the quadratus group (for example, the quadratus lumborum or quadratus femoris) which are roughly square in cross-section. Circular muscles form rings around openings, flat muscles are broad and sheet-like, and pennate muscles have fibers arranged like a feather attaching to a tendon. So the descriptor that directly conveys a four-sided shape is quadrate.