| Column Section | Abbreviation | Vertebrae (typical) | Notes |
|---|---|---|---|
| Cervical | C1–C7 | 7 | Includes atlas (C1) and axis (C2) |
| Thoracic | T1–T12 | 12 | Articulate with ribs |
| Lumbar | L1–L5 | 5 | Largest movable vertebrae |
| Sacral | S1–S5 | 5 (fused) | Fused into single sacrum bone |
| Coccygeal | Co1–Co4¹ | 3–5 (typically 4) | Fused into coccyx (“tailbone”) |
¹ The coccygeal count varies between individuals (3–5), most commonly four.
Altogether, adults have 33 vertebrae before fusion; functionally there are 24 movable vertebrae (C, T, L) plus the sacrum and coccyx.
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