Studies of human algesia have established that the musculoskeletal structures most sensitive to painful stimulation are the periosteum and joint capsules.

NEWYORKER: Backbone

Nelson's injuries destroyed all three main skin layers - the epidermis, dermis and hypodermis (the top, middle and bottom), in some places right down to the periosteum, the membrane overlying the bone.

BBC: US Army seeks new ways to treat facial skin injuries