The spine is a truly remarkable piece of architecture. It comprises of 24 bones called ‘vertebra’.
The neck or cervical spine comprises of 7 vertebrae and is the most moveable portion.
The mid back or thoracic spine comprises of 12 vertebrae. A pair of ribs is attached to each side of these vertebras, forming the rib cage. The design allows it to protect your vital organs and make it less susceptible to injury, but also makes this region of the body very rigid.
The low back or lumbar spine is comprised of 5 vertebrae, which are very large and play a major role in weight bearing for the body. The function and range of movement allowed within this region makes this area prone to injury.
At the base of your spine is a triangular shaped bone called the sacrum, which is part of the pelvis structure and comprises of five-fused vertebra. Attached to the base of the sacrum is a smaller bone called the coccyx, which comprises of four-fused vertebrae.
Viewed from behind, the spine should appear relatively straight, and if there is any sideways distortion then this is called a ‘scoliosis’. Viewed from the side, the spine should have four separate curves. The discs and vertebral bodies are wedged shaped which ultimately allow the spine to curve into this s-shaped configuration. If the thoracic curve is excessive then the person is said to have a ’kyphosis’, and if the cervical and lumbar curves are excessive then the person is said to have a lordosis.
Whether you are standing at a bus stop, sitting in a computer chair, lying in bed or lifting a gym weight, it's important to maintain these postural references mentioned above. Compromising these postural references will increase your chances of injury and develop earlier spinal degeneration.
A typical vertebra comprises of three sections.
1. The Vertebral Body is located at the front part and is the main weight bearing section of the spine. Interverbral discs are attached to the top and bottom surface of these vertebral bodies.
2. The back section is largely composed of spinous and transverse processes whereby muscles and ligaments attach, and also a pair of facet joints that provide the movement and flexibility for the spine.
3. The Spinal Canal is a tunnel formed by the vertebral body at the front and the joints / processes at the back. The spinal cord travels through this canal and is well protected.
Discs are fibro cartilaginous structures which primarily provide a shock-absorbing role for the spinal column.
There is one disc between each vertebra, except for the space between the first and second vertabra. There are 23 discs in total: 6 in the neck (cervical region), 12 in the middle back (thoracic region), and 5 in the lower back (lumbar region). As an example, the disc between the 5th and 6th cervical vertebra is designated "C5-6". The disc between the 7th and 8th thoracic is designated "T7-8". The disc between the 1st and 2nd lumbar is designated "L1-2".
Intervertebral discs consist of 2 sections. The outer section is called the annulus fibrosus and inner section is called the nuclear pulposus.
1. The outer annulus fibrosus consists of several layers of very strong fibrocartilage material. These annular fibers surround the nucleus pulposus within and distribute pressure evenly across the disc.
2. The nucleus pulposus is shaped like a small marble and contains loose connective tissue fibers suspended in a mucoprotein gel with the consistency of jelly. The nucleus of the disc acts as a shock absorber, absorbing the impact of the body's daily activities and keeping the two vertebrae separated.
The disc can be likened to a jelly doughnut: whereby the annulus fibrosis is similar to the dough and the nucleus pulposus is the jelly. If one presses down on the front of the doughnut the jelly will move to the back. When one develops a prolapsed disc the jelly/nucleus pulposus is forced out of the doughnut/disc and may put pressure on the nerve located near the disc. This can give a person the symptoms of sciatica, which is pain down one or both legs.
Disc Pressure in Different Body Positions…
Your spinal cord, along with your brain, forms your central nervous system. The spinal cord is approximately 18 inches long and half an inch thick. All vertebra form a central canal through which the spinal cord can pass. There are 31 pairs of nerves that branch out from the spinal cord, at each vertebral level, and travel throughout your body. These nerves carry commands to your organs and muscles and relay information relating to touch, pain and temperature.
Approximately 400 muscles work together to stabilise your spine, maintain proper posture and allow movement. More than 1000 tendons connect these muscles to your bones. Ligaments are bands of connective tissue that attach bones to bones and help maintain stability and alignment.