The human body is one of the most marvelous creations - it is more complex than the most intricate man-made machines. The spinal column is a part of this complex anatomical composition - the human body. It is also called the spine or the vertebral column, and is situated in the dorsal side of the human body. It starts from the base of the skull and extends to the pelvic region. This flexible structure provides support to the body and also helps in three-dimensional movements.
The spinal column consists of many small cylindrical bones called vertebrae, arranged in a vertical manner. Each individual vertebra is separated from the adjacent ones with a cushion of cartilage called the intervertebral disc. The vertebrae are stacked in such a manner that the roundish holes in successive articulated vertebra form a tunnel. This is called the spinal canal, which houses the spinal cord. The spinal cord, enclosed within the spinal column, is a long, thin bundle of nerve fibers, that extends from the brain and runs through the spinal canal. It is surrounded by a fluid called cerebrospinal fluid, which protects the nerves. These nerves carry messages from the brain to different parts of the body and vice versa.
Normally, the spinal column is made up of 33 vertebrae. Each vertebra consists of an anterior portion with a bony arch, which encloses the vertebral foramen (the large hole in the center), a posterior portion with a spinous process (can be felt through the skin in cervical and lumbar regions), and two transverse processes (one on each side). Muscles and ligaments are attached to the various projections in the vertebrae.
A newborn baby's spinal column comprises all the 33 vertebrae. As he/she reaches adulthood, the five sacral vertebrae fuse together to form one single bone. The same happens to the four coccygeal vertebrae. Hence, a normal adult human being has 24 movable vertebrae, followed by two bony structures in the lower back region. Some individuals may have lesser/more number of vertebrae in one region, which is usually compensated for in any other region, except the sacrum and the coccyx. However, the number of cervical vertebrae remains the same.
The spinal column starts with the cervical segment in the neck and ends with the coccygeal segment in the lower back. The size of the vertebrae increases from top to bottom. The lumbar vertebrae are the largest. The 33 vertebrae are divided into five regions, which are described below.
Cervical (neck) vertebrae - C1 to C7: There are seven cervical vertebrae in the spinal column. Among the 24 movable vertebrae, the cervical vertebrae are the smallest. The main function of the cervical vertebrae is to support the skull. The first and second cervical vertebrae, known as the 'atlas' and 'axis' respectively, are shaped in such a manner, that they execute this function properly. The atlas is joined to the occipital bone at the base of the skull. This joint enables the upward and backward movement of the skull. The axis has got a tooth-like projection, which fits into the atlas. This joint enables the movement of the neck. The cervical vertebrae have small bifid spinous processes.
Thoracic (upper back) vertebrae - T1 to T12: The second region consists of 12 thoracic vertebrae. These vertebrae possess long spinous processes and relatively large vertebral foramen. The transverse processes of these vertebrae articulate with the rib bones. This feature restricts the movement of the thoracic vertebrae to some extent.
Lumbar (lower back) vertebrae - L1 to L5: The five lumbar vertebrae form the third region of the spinal column. Compared to other vertebrae, the lumbar vertebrae are larger. They have large spinous and transverse processes. The lumbar vertebrae also possess small accessory processes, that attach them with the back muscles.
Sacral vertebrae (fused) - S1 to S5: In an adult, the five sacral vertebrae fuse together to form a single bone called the sacrum. It does not contain any intervertebral disc. The sacrum articulates with the last lumbar vertebra located above it and the coccyx below. It also has joints with the iliac bones (part of hip bone) on both sides.
Fused coccygeal vertebrae (tailbone): The four coccygeal vertebrae fuses to form a single bone (coccyx), which is the last segment of the spinal column. Like the sacrum, this region also lacks intervertebral disc. It articulates with sacrum through a fibrocartilaginous joint.
A side view of the spinal column shows four curves corresponding to the different regions. These curves, called the cervical curve, thoracic curve, lumbar curve and the pelvic/sacral curve, help humans to stand upright and maintain the proper balance of the body. While the thoracic curve is the least prominent one, the lumbar curve is more marked in females. Both thoracic and pelvic curves are called the primary curves, as they are present in the fetal stage itself. The lumbar and cervical curves are secondary ones, because they develop after birth. The cervical curve is developed when the infant starts holding his/her head erect. The lumbar curve is developed when the child begins to walk.
- The spinal column supports the body and the skull; helps in standing upright; and maintains the balance of the body.
- Permits flexible movement; helps in head and neck movements. It also allows the body to stretch, bend, lean, and rotate.
- Protects the spinal cord and internal organs, like the lungs and the heart, which are inside the rib cage.
- Provides a base for attachment of muscles, ligaments and tendons.
- The bone marrow inside the bones of the spinal column produces red blood cells and stores minerals.
- Connects the upper body to the lower body.
- The intervertebral discs act like a shock absorber in the body.
The most common ailment of the spinal column is injury to the vertebra. Usually it is caused by sudden and violent movements, which result in inflammation and severe pain in the injured area. In some cases, the spinal cord can suffer damage, which in turn affects the functions of nerves.
Discitis or disc space infection: This disease causes inflammation of the intervertebral discs, and is characterized by severe pain. Though it affects people of all age groups, children are more susceptible. Treatment includes antibiotics and restriction of movement with braces.
Scoliosis: This is characterized by abnormal sideways curvature of the backbone. It can be congenital or developed at a later stage as a secondary symptom of other disorders, like cerebral palsy. In severe cases, the symptoms include chest pain and shortness of breath. Usually, it does not cause back pain. The treatment may vary according to the severity of the curve. While some patients require bracing and surgery, long-term observation is recommended for others.
Vertebral osteomyelitis: In this disease, the bones in the spinal column are affected by bacteria or fungi. Men above the age of 50, diabetics, those affected by tuberculosis, and intravenous drug abusers, are vulnerable to this disease. Common symptoms of vertebral osteomyelitis are back pain and neck pain. Fever and bone fracture may also occur in later stages. Early stages of the disease can be treated with antibiotics, failure of which leads to surgery.
Degenerative disc disease: This disease is caused by the wear and tear of intervertebral discs with advanced age. However, young people may also develop this condition. Symptoms of degenerative disc disease include back pain or neck pain, as the disease commonly occurs in the lumbar and cervical spine. It can be treated with physiotherapy, exercise, medication, and surgery.
Lumbar Hyperlordosis: The lumbar curve is more exaggerated than the normal proportion. It causes stress to other parts of the spine and results in pain. This disorder is most commonly seen in dancers. Stretching exercises and implantation of braces may provide relief.
Kyphosis: The condition is characterized by exaggerated outward curvature of the thoracic spine, forming a humpback. It can be congenital or caused by nutritional deficiencies and faulty postures. The patient may experience breathing problem, chest pain and weakness, in extreme conditions. Treatment includes braces and surgery.
Spinal tumor: As in any other part of the body, tumor may develop within, near, or in the bones of the spinal column.
In case of any injury or disorder to the spinal column, it is advisable to seek expert advice at the earliest. Though we simply refer to it as the backbone, it is a complex structure with intricate functions. Any serious impairment to this body part can result in dire consequences. So it can be considered the 'backbone' of our wellness.