Spinal column or spine provides the main support for the body, allowing the body to stand upright, bend, and twist, while protecting the spinal cord from injury. The spine is made of 33 individual bones (vertebrae) stacked one on top of the other. Strong muscles, flexible tendons and ligaments, and sensitive nerves are surrounding the spine. Any of these structures affected by strain, injury, or disease can cause pain.
Spinal nerves and acupuncture
Spinal nerves are mixed nerves carrying motor, sensory and autonomic nerve fibers and conducting signals to innervate whole body. There are 31 pairs of spinal nerves which are on each side of the spinal column. They are divided into four groups by their location: eight pairs of cervical nerves at the neck, twelve pairs of thoracic nerves at the upper back, five pairs of lumbar nerves, five pairs of sacral nerves and one pair of coccygeal nerves. Motor nerves innervate muscles and bring nerve signals to the muscles to perform motion task. Sensory nerves innervate organs, carry different sensory signals to the spinal cord and the brain. Autonomic nerves innervate internal organs such as smooth muscles and glands and a control system for internal organ function such as cardiac vascular system, respiratory system, digestive system, urinary system and reproductive system. If there is a problem with the neck and back, this may irritate autonomic nerves and have related symptoms, such as abnormal urination, infertility, indigestion, diarrhea or constipation etc.
Muscles, tendons and ligaments problems are very common.
There are two main muscle groups that affect the spine are extensors and flexors. The extensor muscles which are attached to the back of the spine enable us to stand up and lift objects. The flexor muscles which are in the front and include the abdominal muscles enable us to flex, or bend forward, and are important in lifting and controlling the arch in the lower back. The ligaments are strong fibrous bands that hold the vertebrae together, stabilize the spine, and protect the discs. There are two ligaments anterior longitudinal ligament and posterior longitudinal ligaments which located in the front and at the back of vertebras separately and run from the top to the bottom of the spinal column. They prevent excessive movement of the vertebral bones. Between the lamina of each vertebra there are also ligaments attached called ligament flavum. Between adjoining spinous processes of each vertebra thin and membranous Interspinous ligament is attached. They limit the flexion of the spine. Supraspinous ligament lie on the tips of the spinous processes from the seventh cervical vertebra to the sacrum. They continue above seventh cervical vertebra with ligament nuchal. They limit the over flexion of the spine.
How tendon changes with aging
Aging is natural and inevitable. The rate of aging is highly individual and depends on many factors, including genetics, lifestyle, and former disease processes. The degenerative changes can be seen in late thirties. Tendon also has aging changes. There are many cellular and vascular changes within the aging tendon. As a result the aged tendon becomes weaker than it used to be and more likely to tear or get overuse injury, when there is increased stress and strain. With aging process, the density of tendon cells decrease and nucleus becomes bigger, long and thin; cell metabolic activity decreases such as protein and amino acids synthesis. Extracellular changes occur with aging: for example, Elastic fibers and water content decrease which contribute to the tendon stiffness and gliding reduction; collagen content changes little, but the relative amount of collagen, volume density and mechanical stiffness increase due to decrease of water content; collagen synthesis and mechanical properties, solubility decrease. Blood Vessels in tendon change. Tendon blood flow and the number of capillaries per unit of surface area decrease with increasing age. The decreased arterial blood flow and thus decreased nutrition and oxygen transport have been suggested to be the main etiological factors behind the age-related tendon degeneration.
How the spine is related to back pain? There are many structures around spine as mentioned above which can be the source of back pain. For example, nerves around the spine are irritated; muscles are strained; ligaments, bones and joints are injured are worn; disc is slipped etc.
Gravity line and gravity center
The human body encounters gravity constantly in posture and movement. There is gravity line and gravity center of the body. The gravity line is located frontally along a vertical line passing through the middle of the sacrum (lower spine) and perpendicular to the ground, and laterally through a vertical line situated slightly to the rear of the femoral heads. This gravity line must fall within the base of support. The gravity center of the human body is the point where the human body rests under normal conditions without rotating, remaining balanced without active effort to remain upright. This center lies in anterior to the second sacral vertebra and it shifts following the posture and movement to keep the body in balance without falling. When the gravity line falls outside supporting base, compensation is required. Long term compensation can result in overuse the muscles and create inflammation causing pain. Such as low back pain.