Body of the Vertebra
Irregular Bone; part of the axial skeleton (the central core)
Also known as: Vertebral drum, Spinal block, Centrum
Classification
Irregular Bone; part of the axial skeleton (the central core)
Dimensions
In mammals, these structures vary from small, thin discs in the neck to large, heavy cylinders in the lower back. They are typically wider than they are tall to provide a stable base for the spine.
Key Features
The most distinguishing feature is its solid, cylindrical or kidney-shaped appearance. It acts as the 'front' pillar of the vertebra. Look for the flat top and bottom surfaces where shock-absorbing pads normally sit, and the lack of large holes passing through the solid bone itself.
Similar Bones
From the top, it can be confused with a short limb bone fragment. However, you can tell it is a vertebral body by the presence of a large central opening (the neural canal) directly behind it and the small bony wings (processes) extending from its sides and back.
Across Species
The body of the vertebra is the primary weight-bearing component of the spine. In whales, these 'centrums' are massive and almost circular to support their huge bulk in water. In contrast, birds have highly flexible neck vertebrae with saddle-shaped bodies that allow for a wide range of motion, while fish vertebrae often have hourglass-shaped bodies to facilitate side-to-side swimming movements.
Evolutionary History
The vertebral body evolved from simpler structures called intercentra and pleurocentra found in early tetrapods. Over millions of years, these elements fused into the solid, singular 'centrum' seen in modern mammals, providing the necessary rigidity for life on land while protecting the spinal cord within the arch behind it.
Photography Tips
To identify these in the field, take a clear photo looking straight down at the flat surface (top view) and another from the side. Placing a coin or a ruler next to the bone helps establish the scale of the animal it came from.
Notes
What is the arrow pointing to?