Low Back Anatomy
Low Back Anatomy
The anatomy of the low back is very complex, involving structures which support the compressional force of gravity, support the locomotion system, support an incredible degree of movement and consists of different levers and joints with their supporting structures and the muscles which move or stabilize them. Most doctors have only a very rudimentary understanding of spinal anatomy, and much less of an understanding of the spines biomechanics.
We are taking a specific look at the anatomy and biomechanics of the lower back. It must be understood that the lower back functions as a unit with the rest of the body and cannot be isolated from these other regions. For our instructional purposes we will look specifically at the lower back, but for a proper treatment program to work the entire body must be looked at collectively.
This is not meant as a comprehensive anatomy lesson, we will discuss the most relevant anatomy as it relates to the lower back with the idea of a layman who is interested in the cause and treatment their low back can arm themselves with information. A full anatomical discussion would take volumes of information, especially when considering bones, muscles, tendons, ligaments, nervous system, joints, discs, etc.
The spinal column is basically a stack of bones which encircle the spinal cord. At the most basic level the spinal column provides a bony armor protection to the vulnerable spinal cord.
The spinal column consists of 24 bones called vertebrae. It is divided into 4 sections, cervical, thoracic, lumbar and pelvic. There are anatomical as well as biomechanical differences in each of these sections which provide different degrees of movement and support. The cervical section consists of 7 vertebral bones and form the neck. The thoracic section consists of 12 vertebral bones and form the mid back. The lumbar, or low back section consists of 5 vertebral bones. The pelvic or sacral section consist of 5 bones in childhood which fuse to become one large bone called the sacrum.
Looking at a single vertebrae from an overhead view we see some distinctive and important features. Each vertebra has 3 joints which articulate with corresponding joints on the vertebra above and below it. The first joint is the body itself, the vertebral body above and below this one stacks up with a soft compressive disc in between. The other 2 joints are formed by the articular facet joints which are located in the rear. These 3 joints form a tripod and are crucially important to how the spine functions.
Looking at the vertebral column from the side we see the “stack” of vertebral bones. In front a joint is formed when the body of a vertebrae stacks on top of another body with a vertebral disc in between. In the rear an articular facet joint is formed by the articulating facet of the vertebrae above and below meeting, there is on on the left and right side. From this view we can also see the foramen which is a hole formed by each vertebral pair which allows nerves to pass through. This allows the spinal cord, which carries important neurological signals from the brain, to branch out into nerves and exit the bony vertebral column where they can reach other structures of the body to control and modulate them.