Vertebra: A vertebra is one of 33 bony segments that form the spinal column of humans. There are 7 cervical, 12 thoracic, 5 lumbar, 5 sacral (fused into one sacrum bone) and 4 coccygeal (fused into one coccyx bone). From Healthy Resources 10 Rheumatoid Arthritis Symptoms10 Ways to Take Control of Your MigraineHigh-Risk Myelofibrosis: Treatment Options Featured Centers What Are the Best PsA Treatments for You?Understanding Biologics 10 Things People With Depression Wish You Knew