The number of vertebrae in the backbone of a human depends on their age and sex. However, on average, an adult human has 33 vertebrae in their backbone. Let us discuss this in detail.

Anatomy of the Backbone:

The backbone, also known as the spinal column or vertebral column, is a flexible and strong structure that extends from the base of the skull to the pelvis. It comprises of small bones called vertebrae that are separated by intervertebral discs.

The vertebrae are classified into five regions based on their location and shape. These are:

1. Cervical region - 7 vertebrae present in the neck
2. Thoracic region - 12 vertebrae present in the upper back
3. Lumbar region - 5 vertebrae present in the lower back
4. Sacral region - 5 fused vertebrae present in the pelvis
5. Coccygeal region - 4 fused vertebrae present at the end of the backbone

Total number of vertebrae:

The total number of vertebrae in the backbone of a human varies according to their age and sex.

1. An adult human has 33 vertebrae. These include 7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral, and 4 fused coccygeal vertebrae.

2. An infant has 33 vertebrae at birth, but as they grow, the 5 sacral and 4 coccygeal vertebrae fuse together to form the sacrum and coccyx, respectively. Therefore, an adult has only 24 movable vertebrae.

3. The number of vertebrae can also vary between males and females. In general, males tend to have more lumbar vertebrae, while females tend to have more thoracic vertebrae.

Conclusion:

In conclusion, the backbone of an adult human consists of 33 vertebrae, including 7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral, and 4 fused coccygeal vertebrae. The number of vertebrae in the backbone can vary according to age and sex.