What do we call bones that develop within tendons?

Bones that develop within tendons are specifically known as sesamoid bones. These bones form in response to the mechanical stress that occurs due to the pull of a tendon. The most well-known example of a sesamoid bone is the patella (kneecap), which is embedded in the tendon of the quadriceps muscle.

Sesamoid bones serve several purposes: they can modify the direction of muscle forces, increase the mechanical advantage of muscles, and help protect tendons from excessive wear and tear. Their presence can also improve the efficiency of movement by acting as a pulley for tendons.

Other types of bones, such as flat bones, irregular bones, and long bones, do not develop in this manner. Flat bones are typically found in areas such as the skull and are primarily involved in protecting organs and providing surfaces for muscle attachment. Irregular bones have complex shapes and functions, found in places like the vertebrae, while long bones are characterized by their elongated shape and are essential for leverage and movement, as exemplified by the femur and humerus.