The Spine
Understanding Spinal Anatomy
To understand spinal disease, it helps to understand the the anatomy of the spine. Knowing the names of different parts of the spine can also help you have more informed discussions with your doctor about your condition.
Vertebrae
The bony spine is usually made up of 24 back bones called vetebrae. They are stacked one on top of the other and provide a pillar of support for your head and body, and enclose and protect a column of nerve tissues called the spinal cord. The entire body is attached to the spine and nerves. There are five (5) lumbar, or lower back, vertebrae, twelve (12) thoracic, or chest vertebrae, and seven (7) cervical or neck verebrae. The vertebrae make up the front of the pillar.
Pedicles
Each vertebrae has two walls, one on each side making up the sides of the pillar, called pedicles. The pedicles serve to protect the sides of the nervous system and create the walls for the back of the pillar.
Lamina
For each vertebra, two lamina leave the pedicles, slope upwards and meet to form the roof of your spinal canal protecting your spinal cord. This is the back of the pillar.
Spinous Processes
There are slender bones protruding from each of your vertebrae, from the top of the convergence of the lamina and are called the spinous processes. The tips of these bones create the “bumps” you feel when you run your fingers down the middle of your back.
Facet Joints
Between the lamina and the pedicles there is another joint in the spine called the facet joint. There are two on each vertebral body. They serve to stabilize the rotation of each vertebra. Each joint has a lining or synovium, just like any other joint in the body.
Discs
The intervertebral discs are between the vertebrae. These joints act as cushions or shock absorbers. Each disc is made up of a tough, flexible outer band called the annulus fibrosus. Inside the annulus is a soft gel-like substance called the nucleus pulposus.
Ligaments
The 24 vertebrae are connected by soft elastic bands of tissue called ligaments. One of these important ligaments is the ligamentum flavum. This large, long, and strong ligament runs inside of the spinal canal connecting the laminae of the vertebrae.
The ligamentum flavum stabilizes the spine—preventing too much motion between the vertebral bodies.
Another ligament, called the intraspinous ligament, passes over and connects the tips of the spinous processes.
Neural Foramen
At each vertebral level a nerve exits from the spinal cord and leaves the spinal canal through an opening called a neural foramen. This exit hole out of the spine is bordered anteriorly by the intervertebral disc, on the top and bottom by the pedicle and posteriorly by the facet joint. The nerve leaves the spinal canal horizontally traveling to muscles and organs in the body.
The Spinal Cord
The spinal cord is the main input and output from the brain. It extends from the base of the brain to about the level of the first lumbar vertebra. The spinal cord itself is quite fragile and is protected by the surrounding bone and ligaments of the spine.
Nerves branch out of the spinal cord between each side of the vertebra, one to the left and one to the right. At each vertebral level of the spine, nerves from the spinal cord exit the spine through neural foramen and travel to enervate the entire body. In the neck area the nerves enervate the arms and in the lumbar area, the legs.