How many vertebrae make up the adult human spine?

How many vertebrae make up the adult human spine?

• A. 32 vertebrae
• B. 33 vertebrae
• C. 34 vertebrae
• D. 35 vertebrae

Answer: (B)

Counting vertebrae depends on whether you’re counting the original vertebral segments or the fused bones seen in an adult. The spine has 7 cervical, 12 thoracic, and 5 lumbar vertebrae, which totals 24. There are also 5 sacral vertebrae and 4 coccygeal vertebrae that, in adulthood, fuse to form the sacrum and coccyx. If you count each original vertebral segment, you have 24 + 5 + 4 = 33 vertebrae. In an adult, the sacrum and coccyx are fused into single bones, so the number of discrete bones is 26, but when asked for vertebrae, the count 33 reflects the number of vertebral segments before fusion.

Counting vertebrae depends on whether you’re counting the original vertebral segments or the fused bones seen in an adult. The spine has 7 cervical, 12 thoracic, and 5 lumbar vertebrae, which totals 24. There are also 5 sacral vertebrae and 4 coccygeal vertebrae that, in adulthood, fuse to form the sacrum and coccyx. If you count each original vertebral segment, you have 24 + 5 + 4 = 33 vertebrae. In an adult, the sacrum and coccyx are fused into single bones, so the number of discrete bones is 26, but when asked for vertebrae, the count 33 reflects the number of vertebral segments before fusion.