Final answer:
The subject in question refers to a flat bone, consisting of an outer compact bone layer with an inner spongy bone layer, that offers protection to internal organs.
Step-by-step explanation:
The structure being described is that of a flat bone, which is generally thin and composed of two nearly parallel plates of compact bone enclosing a layer of spongy bone, also known as diploë. Flat bones, such as the bones of the cranium, are constructed in such a way that they provide protection for internal organs. The compact bone forms the dense outer layer, while the spongy bone, which is lighter and more porous, can be found in the center. The compact bone layers and the interior spongy bone work together to protect vital areas. For example, if the outer layer of a cranial bone fractures, the brain is still protected by the intact inner layer.