Your spine is made up of interlocking bones called vertebrae. The vertebrae protect the spinal cord, which runs through the central cavity of the vertebral column.
The vertebrae differ in size and shape depending on where in your spine they sit. There are usually:
- 7 cervical vertebrae (the neck region of the spine);
- 12 thoracic vertebrae; and
- 5 lumbar vertebrae (the lower back region).
Your sacrum (made up of 5 fused vertebrae) and coccyx sit at the bottom of your spine.
The part of the vertebra called the spinous process is located at the back of each vertebra. The size and shape of each vertebral spinous process differs depending on where in the spine it is located.
Intervertebral discs sit between the vertebrae and function as cushions. The intervertebral discs are made of cartilage and one of their main functions is to help absorb and reduce shock from movement.
Your spinal cord is a long cylindrical structure of nerve tissue that is about 45 cm long and up to 1 cm in diameter. It sits within the vertebral column (bones of the spine) and is a communication pathway between your body and brain.
The spinal cord contains motor neurones (nerves) that allow us to move our muscles and sensory neurones that receive sensory input, such as feelings of pain, touch and temperature. The spinal cord also contains the nerve circuits that are responsible for spinal reflexes (such as the knee jerk reflex).
The dura mater (or dura) is a membrane that covers and protects the brain and spinal cord. It is the outer layer of the so-called meninges, which are made up of 3 layers — pia mater, arachnoid mater and dura mater.
Spinal nerves arise from the spinal cord and exit the vertebral column in pairs — there are 31 pairs in total. Each spinal nerve has 2 roots — the anterior (front) root is the motor root that controls muscle movements and the posterior (back) root is the sensory root that carries information on sensation.
2. Marieb EN. Essentials of human anatomy and physiology. 10th ed. Redwood City, CA: Benjamin/Cummings; 2011.