What are the four layers of a inside bone?

The four layers of an inner bone are:

1. Compact Bone: The dense outer layer that provides strength and support.
2. Spongy Bone: The lighter, porous inner layer that contains marrow and helps reduce bone weight.
3. Bone Marrow: The soft tissue found within the cavities of bones, responsible for blood cell production.
4. PeriOSteum: The outer membrane that covers the bone, containing nerves and blood vessels, and playing a key role in bone growth and repair.