How are muscles attached to bone?

Muscles attach to bones primarily through tendons, aponeurosis, and can also have direct attachments to bones. Tendons are robust cords of dense connective tissue that connect muscles to bones, allowing for the transmission of force when a muscle contracts, thereby enabling movement at a joint.

Aponeurosis is a broad, flat sheet-like structure of tendon tissue that provides a larger attachment area for muscles, particularly in regions where muscle fibers spread out and attach over a wide area. For instance, the abdominal muscles often connect to the pelvis and the ribs via aponeurotic sheets.

Additionally, certain muscles can attach directly to bones through the muscle fibers themselves, where the fibers penetrate the periosteum (the outer layer of bone), forming a direct connection. This type of attachment can be seen in some facial muscles.

While ligaments connect bones to other bones and cartilage serves as a cushioning interface in a joint, they are not responsible for attaching muscles to bones. Thus, the most comprehensive answer regarding how muscles are attached to bones involves the structure and role of tendons, aponeurosis, and the potential for direct muscle-bone connections.