Spinous Process of the Vertebra
Irregular bone feature belonging to the axial skeleton (the central core of the body).
Also known as: Backbone crest, spinal ridge, neural spine
Classification
Irregular bone feature belonging to the axial skeleton (the central core of the body).
Dimensions
These projections vary significantly in length and thickness depending on their location in the back. In the neck, they are often short and split; in the mid-back, they are long and point downward; in the lower back, they are thick, rectangular, and project straight back.
Key Features
This is the 'fin' or 'thorn' that sticks out from the back of each individual backbone segment. When you run your fingers down your back, the hard bumps you feel are the tips of these processes. They typically look like a flattened plate or a tapering spike originating from the arch of the vertebra.
Similar Bones
It can be confused with the transverse processes, which are the 'wings' sticking out to the left and right sides of a vertebra. To tell them apart, look for the midline orientation; the spinous process always points toward the back/centerline of the body, whereas transverse processes point out toward the sides.
Across Species
The spinous process serves as a lever for muscles and varies wildly across the animal kingdom. In bison, these processes in the shoulder region are exceptionally long, forming the skeletal foundation of their massive hump. In some dinosaurs like Spinosaurus, they grew into enormous sails for display or temperature regulation. In birds, these features are often fused or reduced to streamline the body for flight.
Evolutionary History
These bony projections first appeared in early vertebrates to stabilize the spinal column and provide anchor points for more complex swimming muscles. Over millions of years, as animals transitioned from water to land, the spinous processes became sturdier and angled differently to support the weight of the body against gravity and facilitate walking and running.
Photography Tips
For the best identification, photograph the vertebra from the side (profile view) to show the angle and length of the process, and from the top-down view to show how it relates to the main circle of the bone. Placing a coin or ruler next to it helps show the scale.
Notes
What is the highlighted part?