How does spine work

Thoracic mid back - the main function of the thoracic spine is to hold the rib cage and protect the heart and lungs. The twelve thoracic vertebrae are numbered T1 to T The range of motion in the thoracic spine is limited.

Lumbar low back - the main function of the lumbar spine is to bear the weight of the body. The five lumbar vertebrae are numbered L1 to L5. These vertebrae are much larger in size to absorb the stress of lifting and carrying heavy objects.

Sacrum - the main function of the sacrum is to connect the spine to the hip bones iliac. There are five sacral vertebrae, which are fused together.

Together with the iliac bones, they form a ring called the pelvic girdle. Coccyx region - the four fused bones of the coccyx or tailbone provide attachment for ligaments and muscles of the pelvic floor.

While vertebrae have unique regional features, every vertebra has three functional parts Fig. Each vertebra in your spine is separated and cushioned by an intervertebral disc, which keeps the bones from rubbing together. Discs are designed like a radial car tire. The outer ring, called the annulus, has crisscrossing fibrous bands, much like a tire tread. These bands attach between the bodies of each vertebra.

Inside the disc is a gel-filled center called the nucleus, much like a tire tube Fig. Discs function like coiled springs. The crisscrossing fibers of the annulus pull the vertebral bones together against the elastic resistance of the gel-filled nucleus. The nucleus acts like a ball bearing when you move, allowing the vertebral bodies to roll over the incompressible gel.

The gel-filled nucleus contains mostly fluid. This fluid is absorbed during the night as you lie down and is pushed out during the day as you move upright. With age, our discs increasingly lose the ability to reabsorb fluid and become brittle and flatter; this is why we get shorter as we grow older.

Also diseases, such as osteoarthritis and osteoporosis, cause bone spurs osteophytes to grow. Injury and strain can cause discs to bulge or herniate, a condition in which the nucleus is pushed out through the annulus to compress the nerve roots causing back pain. On the back of each vertebra are bony projections that form the vertebral arch.

The arch is made of two supporting pedicles and two laminae Fig. The hollow spinal canal contains the spinal cord, fat, ligaments, and blood vessels.

Under each pedicle, a pair of spinal nerves exits the spinal cord and pass through the intervertebral foramen to branch out to your body. Surgeons often remove the lamina of the vertebral arch laminectomy to access the spinal cord and nerves to treat stenosis, tumors, or herniated discs. Seven processes arise from the vertebral arch: the spinous process, two transverse processes, two superior facets, and two inferior facets.

The facet joints of the spine allow back motion. Each vertebra has four facet joints, one pair that connects to the vertebra above superior facets and one pair that connects to the vertebra below inferior facets Fig. The ligaments are strong fibrous bands that hold the vertebrae together, stabilize the spine, and protect the discs. The three major ligaments of the spine are the ligamentum flavum, anterior longitudinal ligament ALL , and posterior longitudinal ligament PLL Fig.

The ALL and PLL are continuous bands that run from the top to the bottom of the spinal column along the vertebral bodies. They prevent excessive movement of the vertebral bones. The ligamentum flavum attaches between the lamina of each vertebra. The spinal cord is about 18 inches long and is the thickness of your thumb. There are seven cervical vertebrae in the neck, twelve thoracic vertebrae in the upper back, and five lumbar vertebrae in the lower back.

Each vertebral segment is comprised of a cylinder-shaped bone in the front of the spine, called the vertebral body, a soft cartilage disc between each vertebra, and paired facet joints in the back. The bones in the spinal column surround and protect the spinal cord, which runs behind the vertebral bodies in a canal from the neck down to the top of the lumbar spine.

In the lumbar spine the nerves branch out from the spinal canal and exit the spine in a pattern that resembles a horses tail, called the cauda equina. At each segment, spinal nerve roots exit the spine through holes in the back of the vertebrae called foramen. Any compression of the nerve root in the foraminal opening, which can occur due to bone spurs, herniated or degenerated discs, or facet joint problems, can cause pain and possible neurological symptoms to radiate along the path of the nerve.

These symptoms are commonly called radiculopathy, and leg symptoms may also be called sciatica. In between the vertebrae, the intervertebral discs serve as shock absorbers and help facilitate movement of the spine. The human spine extends from the skull to the pelvis and is made up of individual bones called vertebrae. These are stacked on top of one another and are grouped into four regions:.

The base of the spine, the coccyx tailbone includes partially fused vertebrae. The vertebrae are separated from one another by soft pads, called intervertebral discs, which allow the spine to bend and flex, as well as act as shock absorbers. Throughout the length of the spine, there is a central tube, which is surrounded by bone and discs, called the spinal canal. Inside the canal is the spinal cord, which begins at the base of the brain and ends in the lumbar spine area in a bundle of nerves known as the cauda equina it is said to resemble a horse's tail.

A pair of spinal nerves branch out, right and left, at each vertebral level. The spinal column is responsible for three main functions :. It runs from the base of the skull to the pelvis, and is made up of 33 bones called vertebrae. Each vertebra, apart from the top two, differs in shape and size but has the same anatomy.

They are held together by muscles and ligaments, which provide the back with its flexibility, and are separated by cartilage disks to absorb shock. At each level of the spine, a pair of nerves exit the spinal cord to send messages from the brain to and from various parts of the body. From the front, the spinal column would appear as a straight line. This is known as a non-degenerate spine, meaning it has not suffered from degeneration or deterioration.

The spinal cord is a very important part of the body, acting as the foundation for the central nervous system by linking the brain to the rest of the body. Millions of nerve fibres make up the cord, which is white in colour and approximately the same diameter as a human finger.

The cord is protected from damage by the vertebrae by cerebrospinal fluid CSF. It begins immediately below the brainstem and travels down to the first lumbar vertebrae L1 for approximately 43cm. On its way down the back, 31 pairs of nerves, known as nerve roots, exit the spinal cord through holes in the vertebrae, branching out to various parts of the body.