Stack of bones
The first seven bones are in your neck. They are known as the cervical vertebrae.
The next 12 are called the thoracic vertebrae. The five lumbar vertebrae bear most of your weight. The five sacral vertebrae are fused together. The coccyx consists of four fused vertebrae.
The thoracic vertebrae form joints with the ribs. A straight back is actually quite curvy.
The fused bones of the sacrum and coccyx don’t allow much movement.