A man is shot in the head, and the bullet stops just outside the dura mater. what is the innermost layer that the bullet has penetrated?
The dura mater is inside the skull, which is covered with a periosteum (on both sides), which is covered by fat, which is covered by skin. So to get to "just outside" the dura mater, the bullet penetrated skin, fat, the outer periosteum, bone, and the inner periosteum.