What defines a sesamoid bone?

A sesamoid bone is defined by its positioning, specifically being embedded within a tendon. This unique placement allows sesamoid bones to act as a pulley, which can enhance the mechanical advantage of the tendons that they are associated with. A well-known example of a sesamoid bone is the patella, or kneecap, which is found within the quadriceps tendon. This functional characteristic helps to reduce friction and improve the efficiency of movement.

In contrast to the other choices, sesamoid bones are not limited to specific areas such as just the hand, nor do they possess a flat and thin shape, as their forms can vary. They also do not support the formation of a cavity; that function is typically associated with other types of bones or structures within the skeletal system. Understanding the specific nature and function of sesamoid bones helps to underscore their significance in the biomechanics of movement and joint function.