The human backbone, also known as the spinal column, contains 33 bones at birth, although some fuse later in life. These bones are called vertebrae and are organized into different regions.
Vertebral Regions
Here's a breakdown of the vertebral regions according to the reference:
- Cervical Region: Located in the neck, it has 7 vertebrae.
- Thoracic Region: Located in the upper back, it has 12 vertebrae.
- Lumbar Region: Located in the lower back, it has 5 vertebrae.
- Sacral Region: Located at the base of the spine, it has 5 vertebrae that fuse to form the sacrum.
- Coccygeal Region: Located at the very end of the spine, it has 4 vertebrae that fuse to form the coccyx (tailbone).
Number of Bones in the Adult Backbone
While the spinal column starts with 33 individual bones, the sacral and coccygeal vertebrae fuse during development. This means that adults typically have 24 individual vertebrae (7 cervical + 12 thoracic + 5 lumbar) plus the sacrum and coccyx. Therefore, the number of distinct bones in an adult human backbone is 26.
| Region | Number of Vertebrae at Birth | Number of Bones in Adulthood |
|---|---|---|
| Cervical | 7 | 7 |
| Thoracic | 12 | 12 |
| Lumbar | 5 | 5 |
| Sacral | 5 | 1 (Sacrum) |
| Coccygeal | 4 | 1 (Coccyx) |
| Total | 33 | 26 |
