The spinal column
What is it? A bony structure that protects the spinal cord, the main information highway from the peripheral nerves to the brain. It also provides structure and stability to the skeleton.
Fancy term for this: spine or backbone or vertebral column
The spinal column is made of stacked vertebrae in five regions: cervical (neck), thoracic (thorax/chest), lumbar (lower back), sacral/sacrum (pelvis), and coccyx (tailbone).
The size and shape of the vertebrae vary by region due to slightly different functions because of their position. They are numbered based on their position, except for the tailbone, starting at the base of the head and moving down: C1-C7, T1-T12, L1-L5, S1-S5 (fused).
Each vertebra in the spine is held in place by muscles and ligaments, and it joins the next vertebra via a cartilaginous joint - they’re articulating until S1. Exceptions are the sacral and coccygeal regions, which are fused vestigial vertebrae that form the back of the pelvis in modern humans.
For more information:
Cleveland Clinic - spine anatomy
StatPearls - vertebral column