Understanding The Human Back

Overview

The human back is a large, complex structure composed of bone, muscle, tendons, ligaments, nerves, and blood vessels descending from the back of the neck and shoulders to the top of the buttocks. Its intricate anatomy provides support and flexibility for the head and torso; protection for our internal organs; allows movement of the head, torso, arms, and legs; and most important, serves as the home for the spinal column.

The upper back, consisiting the thorasic section of the spine provides the most support, with the ribs attached firmly to each level of the thoracic spine. The lower back, the lumbar section of the spinal column, allows for flexibility and movement in back bending (extension) and forward bending (flexion). It does not permit twisting.

Skeletal structure of the back

The central skeletal structure of the human back is the vertebral column. This consists of the both the thoracic and lumbar section of the vertebral column which spans from just below the neck to the top of the buttocks. Aside from supporting the head, neck, and torso, the vertebral column also houses and protects the spinal cord – the body’s central information pathway between the brain and body’s peripheral nervous system.

The vertebral column also supports the ribcage, which extends from the top of the thoracic spine, wrapping around each side of the upper torso connecting at the sternum (the center of the chest) The ribcage descends more than halfway down the length of the back, and provides vital protection for several critical organs including the heart and lungs.

Muscles of the back

The back contains a large and complex group of muscles that work together to support the spine, hold the body upright, and allow body’s torso to move, bend, and twist in several directions. The muscles in the back fall into three categories:

  • Extensor Muscles: Attached to the posterior section of the spine, these muscles enable standing and lifting objects.
  • Flexor Muscles: Attached to the anterior section of the spine (including the abdominal muscles), Flexor muscles enable flexing, bending forward, lifting, and arching the lower back.
  • Oblique Muscles: Attached to each side of the spine, Oblique Muscles help rotate the spine and maintain proper posture.
The Spine

The spine - also known as the vertebral column or spinal column - is comprised of 26 bones: 24 separate vertebrae interspaced with cartilage (commonly known as discs), the sacrum (a large, triangular bone at the base of the spine) and the coccyx (more commonly known as the tailbone).

The vertebrae are named by the first letter of their region (Cervical, Thoracic, and Lumbar) combined with a number to indicate their position along the superior-inferior axis. In descending order, there are 7 cervical vertebrae (C1 – C7), 12 thoracic vertebrae (T1 – T12), and 5 lumbar vertebrae (L1 – L5). For example, T1 is the top most vertebrae in the thoracic region and located directly beneath C7.

5 Spinal Regions

Cervical: The 7 vertebrae in the neck form the cervical region of the spine. Although the cervical vertebrae are the thinnest and most delicate vertebrae in the spine, they offer great flexibility to the neck. The first two cervical vertebra, C1 and C2, are named named the Atlas and the Axis respectively and form the joints connecting the skull and spine. The skull pivots on the Atlas when moving up and down, and rotates on the Axis moving right and left.

Thoracic: The 12 vertebrae in the chest region form the spine’s thoracic region. Thoracic vertebrae are larger and stronger than cervical vertebrae but are much less flexible. A unique feature of the thoracic vertebrae is that each one forms joints with a pair of ribs to form the sturdy rib cage that protects the organs of the chest.

Lumbar: The 5 vertebrae in the lower back form the lumbar region of the spine. Lumbar vertebrae larger and stronger than thoracic vertebrae; however, because of the lack of ribs in this region, the lumbar vertebrae are more. Despite the size and strength of the lumbar vertebrae, this region is most associated with back problems due to the fact that all of the upper body’s weight bears down on the lumbar region.

Sacral: The sacral region of the spine contains only the sacrum, a single bone in the adult skeleton that is formed by the fusion of 5 smaller vertebrae during adolescence. The sacrum is a flat, triangular bone found in the lower back and wedged between the 2 hip bones.

Coccyx: The coccyx is a single bone in the adult skeleton that is formed by the fusion of 4 tiny vertebrae during adolescence. In humans, the coccyx bears our body weight when sitting down and provides attachment points for muscles of the pelvic and gluteal regions.

Intervertebral Discs

Discs consist of an outer fibrous ring, the anulus fibrosus, which surrounds an inner gel-like centre, the nucleus pulposus. The anulus fibrosus consists of several layers of fibrocartilage. The strong annular fibers contain and protect the nucleus pulposus, distributing pressure evenly across the disc. The nucleus pulposus contains loose fibers suspended in a mucoprotein gel and act as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.

Back Pain

As stated in the overview section, the human back is complex system of interconnecting nerves, bones, muscles, ligaments, and tendons, all of which can be a source of pain. Medical research studies consistently rate back pain as the second most common type of pain in adults (headaches typically rank first). While muscle strain is the most common cause of back pain, a more serious condition, often chronic in nature, is caused by herniated/ruptured lumbar discs. A herniated disc often requires medical treatment, and they can be extremely painful.

Below is a detailed description of a herniated/ruptured disc as well as the common symptoms.

Herniated Discs

The bones that form the spine (vertebrae) are separated by a gel-like layer called the intervertbral discs. These discs are made up of the outer fibrous ring (the annulus fibrous), and an inner gel-like center (the nucleus pulposus).

These discs act as shock absorbers for the spine as well as allow the back to bend and twist. These spaces also provide an opening for nerves that branch out from the spinal cord to various parts of the body.

Unfortunately, these discs often take a beating. Between supporting the weight of the head and torso, trauma caused by accidents or overuse, and certain medical conditions (like osteoarthritis) can cause damage. If a disc becomes damaged, it may bulge, or break open resulting in a herniated disc. Other common terms for this may be a slipped or ruptured disc. A herniated disc can be extremely painful and greatly affect your ability to move.

Most herniated discs affect the lower back (lumbar spine), because the range of motion is greater and those discs support more body weight. However, a herniated disc can happen anywhere along the spine. Many patients experience disc problems in their neck (cervical spine), or in the upper back (thoracic spine).

A herniated disc is caused by radiculpathy. This is a term used for any disease that affects the spinal nerve root. A slipped/herniated disc is most prevalent in middle-aged and older men. Conditions that are also present at birth that affect the size of the spinal cord, such as spina bifida, can also play a part in herniated discs.

Symptoms

Herniated discs can cause pain, numbness, or weakness in the area of the spine where the disc has ruptured or moved out of place. They can also cause pain, numbness, or weakness in other areas of the body.

  • A herniated disc in the lower back (lumbar spine) may cause sharp pain or numbness in one part of your leg, hip, or buttocks (sciatica pain). The pain may also be accompanied by weakness in that same leg as well.
  • A herniated disc in the neck can cause pain when trying to rotate and/or move the head. Some patients may experience deep pain around the shoulder blade, arms, and fingers. Patients may also experience weakness in certain muscles. In some cases, the pain or weakness may go unnoticed until your doctor examines you.

Pain associated with a herniated disc often starts out slow then gets worse. You may find the pain gets intolerable after standing or sitting, at night, after sneezing or coughing, or even when bending backwards or walking a great distance.

Treatment

Treatment options for herniated discs depend on the area affected and the patient's pain level. What's important to understand is that herniated discs are often a chronic condition, and over time, without treatment, the damage to the affected discs may be irreversible. So if you are experiencing herniated discs problems, please take a moment to read through our treatment section and call our office today to schedule an appointment with Dr. Adamec.