How many intervertebral discs are present in the spine (excluding atlas and axis)?

How many intervertebral discs are present in the spine (excluding atlas and axis)?

• A. 23
• B. 22
• C. 24
• D. 25

Answer: (A)

Intervertebral discs are the cushions between adjacent vertebral bodies. There is no disc between the skull and the first cervical vertebra (atlas) or between atlas and the second cervical vertebra (axis). From C2 down to S1, there is a disc between every pair of consecutive vertebrae. Counting those spaces: there are six between the cervical vertebrae from C2-C3 through C7-T1, twelve in the thoracic region from T1-T2 through T12-L1, and five in the lumbar region from L1-L2 through L5-S1. That adds up to 6 + 12 + 5 = 23 discs. Excluding atlas and axis doesn’t remove any discs because there isn’t a disc at the skull–C1 or C1–C2 junction anyway. Hence, there are 23 intervertebral discs.

Intervertebral discs are the cushions between adjacent vertebral bodies. There is no disc between the skull and the first cervical vertebra (atlas) or between atlas and the second cervical vertebra (axis). From C2 down to S1, there is a disc between every pair of consecutive vertebrae. Counting those spaces: there are six between the cervical vertebrae from C2-C3 through C7-T1, twelve in the thoracic region from T1-T2 through T12-L1, and five in the lumbar region from L1-L2 through L5-S1. That adds up to 6 + 12 + 5 = 23 discs. Excluding atlas and axis doesn’t remove any discs because there isn’t a disc at the skull–C1 or C1–C2 junction anyway. Hence, there are 23 intervertebral discs.