Tendon vs. Aponeurosis — What's the Difference?

Both "tendon" and "aponeurosis" are specialized structures in the body that play crucial roles in the movement and function of muscles. A "tendon" is a strong, cord-like structure made of fibrous connective tissue. It serves as the attachment between muscles and bones. When muscles contract, tendons enable the force to be transferred to bones, thus facilitating movement. "Aponeurosis", meanwhile, is a broad, flat sheet of similar tissue.

In terms of structure, a "tendon" is more cylindrical or cord-like and is often seen at the ends of muscles. These tendons, being relatively inelastic, provide a stable connection that ensures efficient transmission of muscle power to the skeletal system. On the contrary, "aponeurosis" tends to be wider and flatter, providing a large area of attachment. It can connect muscle to muscle or muscle to bone.

Functionally, while both "tendon" and "aponeurosis" assist in transmitting the force produced by muscle contractions, the broader surface area of an aponeurosis can distribute this force over a larger space. This distribution can be especially useful in areas where force needs to be spread out, like in the abdominal region.

To understand their significance, consider the example of the Achilles tendon, one of the strongest and most prominent tendons, connecting the calf muscles to the heel bone. Without it, walking or running would be impossible. Similarly, the aponeurosis in the back, called the thoracolumbar aponeurosis, provides a large attachment area for several significant back and abdominal muscles.