Why Does My Back Hurt?
Basics of the Back
The central feature of the human back is the vertebral column, specifically the length from the top of the thoracic vertebrae to the bottom of the lumbar vertebrae, which houses the spinal cord in its spinal canal, and which generally has some curvature that gives shape to the back. The ribcage extends from the spine at the top of the back (with the top of the ribcage corresponding to the T1 vertebrae), more than halfway down the length of the back, leaving an area with less protection between the bottom of the ribcage and the hips. The width of the back at the top is defined by the scapula, the broad, flat bones of the shoulders.
Functions of the Back
The intricate anatomy of the back provides support for the head and trunk of the body, strength in the trunk of the body, as well as a great deal of flexibility and movement. The upper back has the most structural support, with the ribs attached firmly to each level of the thoracic spine and very limited movement. The lower back (lumbar vertebrae) allows for flexibility and movement while back bending (extension) and forward bending (flexion). It does not permit twisting.
Muscles of the Back
The spine is bordered by several groups of muscles, including the intertransversarii muscle which facilitates movement between the individual vertebrae, and the multifidus spinae, which facilitates the movement of the spine as a whole.
Other muscles in the back are associated with the movement of the neck and shoulders. The trapezius muscle, which is named from its trapezium-like shape, runs between the neck, the anterior chain, the two shoulders, and the thoracic vertebrae, T12. The large latissimus dorsi makes a triangle from the shoulder to the hip.
Vertebrae
The vertebral body is a thin ring of dense cortical bone. The vertebral body is shaped like an hourglass, thinner in the center with thicker ends. The outer cortical bone extends above and below the superior and inferior ends of the vertebrae to form rims. The superior and inferior endplates are contained within these rims of bone.
Pedicles
The pedicles are two short rounded processes that extend posteriorly from the lateral margin of the dorsal surface of the vertebral body. They are made of thick cortical bone.
Laminae
The laminae are two flattened plates of bone extending medially from the pedicles to form the posterior wall of the vertebral foramen. The Pars interarticularis is a special region of the lamina between the superior and inferior articular processes. A fracture or congenital anomaly of the pars may result in a spondylolisthesis.
Intervertebral Discs
Intervertebral discs are found between each vertebra. The discs are flat, round structures about a quarter to three-quarters of an inch thick with tough outer rings of tissue called the annulus fibrosis that contain a soft, white, jelly-like center called the nucleus pulposus. Flat, circular plates of cartilage connect to the vertebrae above and below each disc. Intervertebral discs separate the vertebrae, but they act as shock absorbers for the spine. They compress when weight is put on them and spring back when the weight is removed.
Intervertebral discs make up about one-third of the length of the spine and constitute the largest organ in the body without its own blood supply. The discs receive their blood supply through movement as they soak up nutrients. The discs expand while at rest allowing them to soak up nutrient-rich fluid. When this process is inhibited through repetitive movement, injury, or poor posture, the discs become thinner and more prone to injury. This may be a cause of the gradual degeneration of the structure and dysfunction of the disc over time.
Facet Joints
Joints between the bones in our spine are what allow us to bend backward and forward and twist and turn. The facet joints are a particular joint between each vertebral body that helps with twisting motions and rotation of the spine. The facet joints are part of the posterior elements of each vertebra. Each vertebra has facet joints that connect it with the vertebra above and the vertebra below in the spinal column. The surfaces of the facet joints are covered with smooth cartilage that helps these parts of the vertebral bodies glide smoothly on each other.
Ligamentum Flavum
The ligamentum flavum is a strong ligament that connects the laminae of the vertebrae. The term “flavum” is used to describe the yellow appearance of the ligament in its natural state. The ligamentum flavum serves to protect the neural elements and the spinal cord and stabilize the spine so that excessive motion between the vertebral bodies does not occur. It is the strongest of the spinal ligaments and often has a thinner middle section. Together with the laminae, it forms the posterior wall of the spinal canal.
Spinal Cord
The spinal cord is part of the central nervous system of the human body. It is a vital pathway that conducts electrical signals from the brain to the rest of the body through individual nerve fibers. The spinal cord is a very delicate structure that is derived from the ectodermal neural groove, which eventually closes to form a tube during fetal development. From this neural tube, the entire central nervous system, our brain, and spinal cord, eventually develops. Up to the third month of fetal life, the spinal cord is about the same length as the canal. After the third month of development, the growth of the canal outpaces that of the cord. In an adult, the lower end of the spinal cord usually ends at approximately the first lumbar vertebra, where it divides into many individual nerve roots.
Spinal Canal
The spinal canal is the anatomic casing of the spinal cord. The bones and ligaments of the spinal column are aligned in such a way as to create a canal that provides protection and support for the spinal cord. Several different membranes enclose and nourish the spinal cord and surround the spinal cord itself. The outermost layer is called the “dura mater,” which is a Latin term that means “tough mother,” indicating that early anatomists had a least a rudimentary sense of humor. The dura is a very tough membrane that encloses the brain and spinal cord and prevents cerebrospinal fluid from leaking out from the central nervous system. The space between the dura and the spinal canal is called the “epidural space”. This space is filled with tissue, vessels, and large veins. The epidural space is important in the treatment of low back pain because it is in this space that medications such as anesthetics and steroids are injected in order to alleviate pain and inflammation of the nerve roots.
By learning more about what a complex and vital organ the spine is, we can better understand how to prevent and heal spinal injuries. When an injury occurs, whatever is required depends on what part of the spine is injured, and that is why it is important to have a team of doctors that is able to identify the root injury.
At BBC Health in Lewisville, Texas, we know how to identify, treat, or refer in the proper direction for any problems with your back and spine. As a primary care provider, we can quickly provide medical, chiropractic, and rehab treatments in order to get you well as fast as possible. If you’re suffering from back pain, don’t delay, and contact us immediately to see how we can help.
