Spine
Spinal Column, Backbone
noun, の adjective
せきつい
背 (せ) Height, Back, Spine
脊椎 (せきつい) Spine, Spinal Column, Backbone
骨髄 (こつずい) Bone Marrow, Marrow
脊髄 (せきずい) Spinal Cord
The Spine 脊椎 gives vertebrates stature 脊 and is sturdy like an oak 椎 so it can protect the spinal cord at its center.