Vertebral column : It is formed by 26 serially arranged units called vertebrae and is dorsally placed. It extends from the base of the skull and constitutes the main framework of the trunk. central hollow portion (neural canal) through which the spinal cord passes. It has a central hollow portion (neural canal) through
which the spinal cord passes.  The vertebral column is differentiated into cervical (7), thoracic (12), lumbar (5), sacral (1-fused) and coccygeal (1-fused) regions starting from the skull.  The number of cervical vertebrae are seven in almost all mammals including human beings. The vertebral column protects the spinal cord, supports the head and serves as the point of attachment for the ribs and musculature of the back. The vertebrae are divided into following categories :

1. Cervical vertebrae : These are present in neck. These are seven in number (All mammals have seven cervical vertebrae).

2. Thoracic vertebrae : These are present in thoracic region. There are twelve thoracic vertebrae.

3. Lumbar vertebrae : These are present in abdominal region and are five in number.

4. Sacral vertebrae : There are five sacral vertebrae present in pelvic region. These get fused to form one sacrum.

5. Coccygeal vertebrae : These are four in number and are present below sacrum. These fuse to form one vertebra.