Which type of bone is defined by its expanded area for muscle attachment?

The expanded area for muscle attachment is primarily associated with long bones, which are characterized by their length that is greater than their width and typically have a shaft (diaphysis) and two ends (epiphyses). The epiphyses of long bones often feature specific areas that serve as sites for muscle attachment, such as the greater and lesser tubercles of the humerus where muscles like the rotator cuff attach.

Flat bones, on the other hand, serve primarily protective roles and provide extensive surfaces for muscle attachment, but they do not have an "expanded area" in the same context as the structures found on long bones. Examples of flat bones include the skull, scapula, and sternum.

Irregular bones, like vertebrae, do not have a uniform shape or size and are more variable in their structures and functions, lacking the consistent expanded areas for muscle attachment typically seen in long bones.

Pneumatic bones, such as those found in birds, contain air spaces to reduce weight and help with flight but do not specifically correspond to muscle attachment areas like those found in long bones.

Thus, when considering the definition of bones with expanded areas specifically designed for muscle attachment, long bones are the most relevant category.