Final answer:
Thin, broad bones are correctly categorized as flat bones, which can be thin and curved, serving as points of attachment for muscles and protection for internal organs.
Step-by-step explanation:
Thin, broad bones should be classified as flat bones. Despite the misleading term, flat bones tend to be thin, and can also be curved, as is the case with skull bones, the scapulae, the sternum, and the ribs. These flat bones often serve significant roles in muscle attachment and organ protection.
Irregular bones, on the other hand, refer to bones with complex shapes, such as the vertebrae and certain skull bones. Unlike flat bones, they may have various surfaces that are short, flat, notched, or ridged.
The human skeleton features six types of bones based on shape or location: long, short, flat, sesamoid, sutural, and irregular. As an example, the bones of the limbs, including fingers and toes, are classified as long bones, which are much longer than they are wide and have a distinctive shaft and rounded ends.