Short answer: Bones structures in the head and chest help to protect vital organs, while bones in the limbs are mainly for movement.
Explanation:
Bones are hard structures that serve different purposes depending on their shape and structure. In the case of bones found in the head or the chest including the occipital bone, the ethmoid bone, among others in the head, and the ribs, sternum, etc. in the chest these are flat bones that together form cavities to protect vital organs such as the brain in the head and the heart and lungs in the chest.
On the other hand, bones in the limbs such as the humerus, the tibia, the radius, etc. are considered as long bones. Moreover, this structure supports their function of providing movement to the body rather than protecting organs as it occurs with flat bones.