Vertebra

A vertebra is one of the small bones stacked up to form your spine. Each one has a thick, block-like front part (the vertebral body) that carries most of your weight, plus bony arches in back that protect the spinal cord. There are 24 movable vertebrae, grouped into the neck (cervical), mid-back (thoracic), and lower back (lumbar) regions, plus the fused bones of the sacrum below.

Vertebrae matter a lot in bone health because they're mostly trabecular (spongy) bone, which turns over faster than the dense outer bone in your arms and legs. This makes the spine one of the first places bone loss shows up, and a common site for fragility fractures, especially compression fractures that can happen quietly, without a fall, and sometimes without pain.

Because the lumbar spine is routinely scanned on DEXA, it's also prone to looking falsely dense on the scan. Things like arthritis, old fractures, calcified arteries, or spinal hardware sitting over the vertebrae can push the reported bone density up artificially. That's one reason your doctor may lean more on the hip reading, or add a visual check of the spine, when deciding what your bone density numbers really mean.