Structure of Your Back

[EricS]

Almost all the literature on back pain you are likely to find tosses around a lot of anatomical jargon. Here is a short intro to know your back!

The spine is a remarkable structure made of circular bones called vertebrae. The vertebrae encase the spinal cord, a complex system of nerve roots connecting the brain with the rest of the body.

The spinal column is classified into -

* Cervical Spine (neck region), consisting of 7 vertebrae
* Thoracic Spine (upper back), with 12 vertebrae
* Lumbar Spine (lower back), 5 vertebrae
* Sacral Spine (tailbone), 5 vertebrae

In between each vertebra there are flat round Inter-vertebral Discs, up to 3/4 inch thick, with round cartilages connecting vertebrae above and below. They separate the vertebrae and acting as shock absorbers for the spine. They have a tough outer casing called annulus with a soft jelly like core known as the nucleus.

Joints (the facet joint, for example) between the vertebrae in the spine allow bending, twisting and turning motions.

Muscles like rotators, erector spinae etc. support the spine and helps it move.

Finally there are Ligaments (they control movement of the joints), tendons (attach bones and muscles), joint capsules (encasing the joints and containing lubricating fluids) and cartilages.

[BP4MS]

The National Institute of Health describes the structure of the back as follows:

The back is an intricate structure of bones, muscles, and other tissues that form the posterior part of the body’s trunk, from the neck to the pelvis. The centerpiece is the spinal column, which not only supports the upper body’s weight but houses and protects the spinal cord — the delicate nervous system structure that carries signals that control the body’s movements and convey its sensations.

Stacked on top of one another are more than 30 bones — the vertebrae — that form the spinal column, also known as the spine. Each of these bones contains a roundish hole that, when stacked in register with all the others, creates a channel that surrounds the spinal cord. The spinal cord descends from the base of the brain and extends in the adult to just below the rib cage. Small nerves (“roots”) enter and emerge from the spinal cord through spaces between the vertebrae. Because the bones of the spinal column continue growing long after the spinal cord reaches its full length in early childhood, the nerve roots to the lower back and legs extend many inches down the spinal column before exiting. This large bundle of nerve roots was dubbed by early anatomists as the cauda equina, or horse’s tail.

The spaces between the vertebrae are maintained by round, spongy pads of cartilage called intervertebral discs that allow for flexibility in the lower back and act much like shock absorbers throughout the spinal column to cushion the bones as the body moves. Bands of tissue known as ligaments and tendons hold the vertebrae in place and attach the muscles to the spinal column.

Starting at the top, the spine has four regions:

- the seven cervical or neck vertebrae (labeled C1–C7),
- the 12 thoracic or upper back vertebrae (labeled T1–T12),
- the five lumbar vertebrae (labeled L1–L5), which we know as the lower back, and
- the sacrum and coccyx, a group of bones fused together at the base of the spine.

The lumbar region of the back, where most back pain is felt, supports the weight of the upper body.

[Craftweb]

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 vertebra), 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.

[MGRWPBFL]

[QUOTE=Craftweb;1270]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.

Each section of the spine has a natural curve. Viewed from the side, the cervical and lumbar spines have a lordotic, or slight concave curve, and the thoracic spine has a kyphotic, or gentle convex curve.
Natural curves are important. Without these curves the spine would not have the strength and resilience to act as a shock absorber during movement. The back's curves are designed to absorb shock and to facilitate the full range of motion throughout the spinal column. The natural curves act as a coiled spring to absorb force or jarring during activity. Jogging or jumping rope would be impossible without these curves. The yielding curves are the pillars of strength, resilience, and flexibility in the spine. Nonetheless, our back's flexibility is not without its own set of problems.