OVERVIEWThe spinal column, otherwise known as the backbone, is a complex system made of 33 bony vertebrae supported by strong muscles, flexible tendons and ligaments. The interplay of these structures allows us to stabilize our entire body. This enables us to stand, bend, twist, walk, sit and maintain a certain posture during weight-bearing activities with relative ease. More importantly, this houses and, thus, acts to protect the spinal cord, which is part of the peripheral nervous system that coordinates functions of our body with our brain. Therefore, if this is affected by any disease or is disrupted by injury, this may result to pain, disfigurement or disability.
SPINAL CURVESWhen we are born, our spine is C-shaped. And as we grow old and learn to walk on our feet, we adopt an upright posture so that the weight of our body would constantly pull on our backbone; consequently, it assumes an S-shaped configuration. Viewed from the side, the cervical and lumbar regions have a slight concave curve (lordosis) while the thoracic and sacral regions have a convex curve (kyphosis). This shape, likened to a spring, allows our body to perform a wide range of movement and activities such as sitting, standing, walking, lifting, dancing, without having to put too much strain on the backbone.
VERTEBRAEThirty-three (33) individual bones make up the spinal column and are divided into regions: cervical (7), thoracic (12), lumbar (5), sacral (5), and coccygeal (4). The first 24 vertebrae are movable while the sacrum and coccyx are fused. Three functional parts make up each vertebral bone.
- body - which is the thickest and largest part that is anteriorly oriented, withstands compressive forces
- vertebral arch - which is a partial circle of bone made up of the pedicles and lamina that houses and protects the spinal cord
- posterior star-shaped process - which serves as attachment for muscles and ligaments, stabilizing the spine and protecting the intervertebral discs
Worthwhile to note that each vertebrae also possesses a unique characteristic that is essential in its function.
Cervical region - the seven cervical vertebrae (C1-C7) functions mainly to support the head, allowing the greatest range of motion because of the presence of the atlas (C1), the ring-shaped vertebra that connects directly to the skull; and the axis (C2), the peg-shaped vertabra where the atlas pivots around. Whenever we nod our heads, the atlas is at work. When we move our heads side-to-side, then we are using the axis.
Thoracic region - twelve (12) vertebrae comprise this region (T1-T12). This region particularly has limited range of motion and mainly functions to protect the organs within the chest by serving as points of attachment for the rib cage.
Lumbar region - five (5) lumbar vertebrae (L1-L5) are larger in size to allow the spine to bear the weight of the body.
Sacral region - five (5) sacral bones that are fused together provide attachments to the pelvic bones and protect the pelvic organs.
Coccyx - four (4) fused tailbone that
INTERVERTEBRAL DISCSBetween each vertebra lies a cushion-like structure known as the intervertebral disc that functions as a shock-absorber, keeping the bones from rubbing together. Much like an airsole in rubbershoes, the outer ring of the discs known as the annulus fibrosus which are made of criss-crossing fibers contain within it gel, known as the nucleus pulposus. When we move, the vertebrae merely rolls over the incompressible gel-filled discs, preventing friction and maintaining stability and ease.
However, with age, the gell-like structure looses the ability to reabsorb fluid and thus, becomes more brittle and flat, decreasing ease in movement and agility. Disease can also affect these areas such as osteoarthritis, producing bone spurs that can compress on other structures within and around the spinal column. Injury to these areas can lead to disc bulge or slipped disc that can lead to severe pain over the back and lower extremities and cause major disability.
SPINAL CANALThe spinal canal is housed in the vertebral arch along the posterior of every vertebral body. This canal contains the spinal cord, connective tissues, fat and vascular supply of the cord. From the spinal cord arises spinal nerves that exit under each pedicle to supply parts of the body.
With diseases affecting the spinal cord, most surgeons gain access to this area by removing the lamina (laminectomy) of the vertebral arch. With this maneuver, more room can be made to perform decompression surgeries.
SPINAL CORDInside the spinal canal is a long, tube- like structure that connects our brain to the rest of our body. This structure is our spinal cord. Although long, it does not extend to fill the whole length of the spinal canal. It starts from the base of our brain and tapers in the lumbar area.
The spinal cord facilitates the transmission of motor commands from our brain to the different parts of our body. It is also responsible for returning sensory information such as pain from the nerve endings giving feedbacks to our brain. It also facilitates some of our body’s reflexes.
Being a part of the central nervous system, the spinal cord is protected by the same structures that protect our brain. The outermost layer is the dura mater which provides the strongest protection since this layer is very tough. The middle layer is called the arachnoid mater due to its weblike appearance. The innermost layer is the pia mater which is almost adherent to the spinal cord. Between the arachnoid and the pia mater is where the cerebrospinal fluid is contained.
The spinal cord, when viewed on cross section, is formed by a gray area where the nerve cell bodies are located surrounded by white peripheral area. It is divided into the ventral and the dorsal part. The ventral part gives rise to the motor root while the dorsal part gives rise to the sensory root. The two roots then combine to form the spinal nerve.
SPINAL NERVESThe spinal cord is further divided into segments based on the corresponding vertebra that houses them. In every segment, there is a pair of spinal nerve that arises. Although there are 33 individual vertebra in the spinal column, there is only 31 pairs of spinal nerve that arise from the spinal cord. A total of 8 cervical nerves exits the cervical region inspite 7 cervical vertebra although only 1 coccygeal nerve exits the sacral region due to the fusion of 3 coccygeal segments.
The cervical nerves are responsible for the movement of our neck, shoulders, arms, elbows as well as for breathing. The throracic nerves are responsible for the movement of our hands, trunk, waist and abdomen. The lumbar nerves move our thigh, legs and knee. Our sacral nerves move our foot. In the event of a spinal cord injury, the location of the injury will determine the movement which will be affected.