The spine is make of 33 separation, personal, instance bones stack one on top of the other. This spinal column gives the main support for her body, permitting you to stand upright, bend, and also twist, if protecting the spinal cord native injury. Solid muscles and bones, versatile tendons and also ligaments, and sensitive nerves add to a healthy spine. Yet, any of these structures affected by strain, injury, or disease can reason pain.

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Spinal curves

When viewed from the side, an adult spine has actually a natural S-shaped curve. The neck (cervical) and also low ago (lumbar) regions have actually a slim concave curve, and the thoracic and sacral regions have actually a tenderness convex curve (Fig. 1). The curves occupational like a coiled spring to absorb shock, keep balance, and allow variety of activity throughout the spinal column.

number 1. The spine has three herbal curves that form an S-shape; solid muscles store our spine in alignment.
figure 2. The five regions that the spinal column.

The ab and ago muscles preserve the spine"s organic curves. Good posture requires training her body to stand, walk, sit, and also lie so that the least amount of strain is placed on the spine throughout movement or weight-bearing activities (see Posture). Excess body weight, weak muscles, and also other forces can traction at the spine"s alignment:

an abnormal curve that the lumbar spine is lordosis, also called persuade back. An abnormal curve the the thoracic spine is kyphosis, also called hunchback. An abnormal curve indigenous side-to-side is referred to as scoliosis.


The two main muscle teams that affect the spine space extensors and flexors. The extensor muscles allow us to was standing up and also lift objects. The extensors are attached to the earlier of the spine. The flexor muscles room in the front and include the abdominal muscle muscles. This muscles allow us to flex, or bending forward, and are vital in lifting and also controlling the arch in the lower back.

The back muscles stabilize her spine. Something as usual as negative muscle tone or a large belly have the right to pull your whole body the end of alignment. Misalignment puts incredible strain top top the spine (see practice for a healthy Back).


Vertebrae room the 33 individual bones that interlock v each various other to form the spinal column. The vertebrae are numbered and also divided right into regions: cervical, thoracic, lumbar, sacrum, and also coccyx (Fig. 2). Only the height 24 bones room moveable; the vertebrae the the sacrum and also coccyx are fused. The vertebrae in each region have unique features that assist them execute their main functions.

Cervical (neck) - the main role of the cervical spine is to support the load of the head (about 10 pounds). The seven cervical vertebrae space numbered C1 to C7. The neck has actually the greatest range of motion because of two dedicated vertebrae that connect to the skull. The first vertebra (C1) is the ring-shaped atlas that connects straight to the skull. This joint allows for the nodding or “yes” activity of the head. The 2nd vertebra (C2) is the peg-shaped axis, which has actually a projection dubbed the odontoid, that the atlas pivots around. This joint allows for the side-to-side or “no” motion of the head.

Thoracic (mid back) - the main role of the thoracic spine is to host the rib cage and also protect the heart and lungs. The twelve thoracic vertebrae space numbered T1 to T12. The variety of motion in the thoracic spine is limited.

Lumbar (low back) - the main duty of the lumbar spine is to bear the weight of the body. The 5 lumbar vertebrae room numbered L1 to L5. These vertebrae room much bigger in dimension to absorb the stress of lifting and carrying heavy objects.

Sacrum - the main duty of the sacrum is to attach the spine come the hip bones (iliac). There are 5 sacral vertebrae, which room fused together. Together with the iliac bones, they form a ring dubbed the pelvic girdle.

Coccyx region - the 4 fused skeleton of the coccyx or tailbone provide attachment for ligaments and also muscles the the pelvic floor.

While vertebrae have unique local features, every vertebra has actually three functional components (Fig. 3):



a drum-shaped body designed to bear weight and also withstand compression (purple) an arch-shaped bone that protects the spinal cord (green) star-shaped processes designed as outriggers because that muscle attachment (tan)

Intervertebral discs

Each vertebra in your spine is separated and also cushioned by one intervertebral disc, i m sorry keeps the bones indigenous rubbing together. Discs are designed prefer a radial car tire. The external ring, dubbed the annulus, has actually crisscrossing fibrous bands, much like a tires tread. These bands attach between the body of every vertebra. Inside the key is a gel-filled center called the nucleus, lot like a tire pipe (Fig. 4).



Discs function like coiled springs. The crisscrossing fibers of the annulus traction the vertebral skeleton together versus the elastic resistance that the gel-filled nucleus. The cell nucleus acts prefer a round bearing once you move, permitting the vertebral body to roll over the incompressible gel. The gel-filled nucleus contains mostly fluid. This liquid is absorbed during the night as you lie down and is moved out during the day together you move upright.

With age, ours discs progressively lose the capacity to reabsorb fluid and become brittle and also flatter; this is why we get much shorter as we prosper older. Additionally diseases, such together osteoarthritis and also osteoporosis, cause bone spurs (osteophytes) come grow. Injury and also strain can reason discs come bulge or herniate, a problem in i beg your pardon the nucleus is propelled out through the annulus to compress the nerve root causing back pain.

Vertebral arch & spinal canal

On the back of each vertebra space bony projections that form the vertebral arch. The arch is make of two supporting pedicles and two laminae (Fig. 5). The hollow spinal canal contains the spinal cord, fat, ligaments, and blood vessels. Under each pedicle, a pair the spinal nerves exits the spinal cord and also pass with the intervertebral foramen to branch the end to her body.


Surgeons frequently remove the lamina the the vertebral arch (laminectomy) to access the spinal cord and also nerves come treat stenosis, tumors, or herniated discs.

Seven procedures arise native the vertebral arch: the spinous process, 2 transverse processes, two superior facets, and also two worse facets.

Facet joints

The facet joints the the spine allow earlier motion. Every vertebra has four facet joints, one pair the connects come the vertebra over (superior facets) and one pair that connects to the vertebra listed below (inferior facets) (Fig. 6).

figure 6. The superior and also inferior facets connect each vertebra together. There are four facet joints linked with every vertebra.


The ligaments are strong fibrous bands that host the vertebrae together, stabilize the spine, and also protect the discs. The three significant ligaments of the spine are the ligamentum flavum, anterior longitudinal ligament (ALL), and also posterior longitudinal ligament (PLL) (Fig. 7). The ALL and PLL are continuous bands that run from the optimal to the bottom of the spinal column along the vertebral bodies. Lock prevent excessive movement the the vertebral bones. The ligamentum flavum attaches between the lamina of every vertebra.

figure 7. The ligamentum flavum, anterior longitudinal ligament (ALL), and also posterior longitudinal ligament (PLL) enable the flexion and extension the the spine while keeping the skeleton aligned.

Spinal cord

The spinal cord is around 18 customs long and also is the thickness of your thumb. It runs from the brainstem come the 1st lumbar vertebra safeguarded within the spinal canal. At the finish of the spinal cord, the cord fibers separate into the cauda equina and also continue down v the spinal canal to your tailbone prior to branching off to your legs and feet. The spinal cord serves together an information super-highway, forward messages between the mind and the body. The brain sends motor messages come the limbs and body through the spinal cord enabling for movement. The limbs and also body send sensory messages to the brain through the spinal cord around what we feel and touch. Periodically the spinal cord can react there is no sending info to the brain. These special pathways, referred to as spinal reflexes, space designed to automatically protect our human body from harm.

Any damage to the spinal cord can result in a loss of sensory and also motor function below the level of injury. For example, one injury come the thoracic or lumbar area may cause motor and sensory lose of the legs and trunk (called paraplegia). An injury to the cervical (neck) area may reason sensory and motor ns of the arms and also legs (called tetraplegia, previously known together quadriplegia).

Spinal nerves

Thirty-one bag of spinal nerves branch off the spinal cord. The spinal nerves act together “telephone lines,” moving messages earlier and forth in between your body and spinal cord to control sensation and also movement. Each spinal nerve has two roots (Fig. 8). The ventral (front) root carries engine impulses from the mind and the dorsal (back) root carries sensory impulses to the brain. The ventral and also dorsal roots fuse together to form a spinal nerve, which travels under the spinal canal, alongside the cord, till it reaches its exit hole - the intervertebral foramen (Fig. 9). When the nerve passes with the intervertebral foramen, the branches; every branch has both motor and sensory fibers. The smaller sized branch (called the posterior main ramus) turns posteriorly to supply the skin and muscles that the ago of the body. The bigger branch (called the anterior main ramus) transforms anteriorly to it is provided the skin and muscles of the prior of the body and also forms many of the significant nerves.

figure 8. The ventral (motor) and dorsal (sensory) roots sign up with to kind the spinal nerve. The spinal cord is spanned by 3 layers of meninges: pia, arachnoid and also dura mater.

The spinal nerves space numbered according to the vertebrae above which it exits the spinal canal. The 8 cervical spinal nerves space C1 through C8, the 12 thoracic spinal nerves are T1 through T12, the 5 lumbar spinal nerves are L1 through L5, and the 5 sacral spinal nerves room S1 v S5. Over there is 1 coccygeal nerve.

figure 9. The spinal nerves exit the spinal canal v the intervertebral foramen below each pedicle.

The spinal nerves innervate certain areas and kind a strip pattern across the body called dermatomes (Fig. 10). Doctors use this sample to diagnose the ar of a spinal problem based on the area of pain or muscle weakness. For instance leg pain (sciatica) usually suggests a trouble near the L4-S3 nerves.


number 10. A dermatome pattern shows which spinal nerves room responsible for sensory and motor control of particular areas that the body.

Coverings & spaces

The spinal cord is spanned with the exact same three membranes as the brain, referred to as meninges. The inside membrane is the pia mater, i m sorry is intimately attached come the cord. The next membrane is the arachnoid mater. The external membrane is the tough dura mater (Fig. 8). Between these membranes room spaces offered in diagnostic and also treatment procedures. The an are between the pia and also arachnoid mater is the large subarachnoid space, which surrounding the spinal cord and contains cerebrospinal liquid (CSF). This an are is most often accessed as soon as performing a lumbar puncture come sample and also test CSF or throughout a myelogram come inject comparison dye. The an are between the dura mater and also the bone is the epidural space. This room is most often accessed to supply anesthetic numbing agents, frequently called an epidural, and to inject steroid medication (see Epidural Steroid Injections).

Sources & links

If you have much more questions, please contact the Mayfield brain & Spine at 800-325-7787 or 513-221-1100.

web links

www.spine-health.com www.spineuniverse.com


dorsal: the back or posterior next of the body.

kyphosis: one abnormal forward curvature that the thoracic spine, also called hunchback.

lordosis: an abnormal curvature of the lumbar spine, likewise called swayback.

paraplegia: paralysis of both legs and also lower body listed below the arms indicating one injury in the thoracic or lumbar spine.

quadraplegia: paralysis that both legs and arms indicating an injury to the cervical spine.

scoliosis: an abnormal side-to-side curvature the the spine.

ventral: the former or anterior side of the body.

updated > 9.2018 reviewed by > Tonya Hines, CMI, Mayfield Clinic, Cincinnati, Ohio

Mayfield Certified health Info materials are written and also developed by the Mayfield Clinic. We comply v the HONcode standard for trustworthy health information. This information is no intended to replace the medical advice of your health treatment provider.

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In recent decades medical scientists have actually made a quantum leap in their understanding of the human brain and spinal cord. Their discoveries have been fueled by advances in imaging technology and neurobiology.

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Whether they are studying brand-new surgical techniques, participating in clinical trials, or quantifying outcomes, Mayfield clinician researchers space working every work to discover what works best for our patients. Meanwhile, the Mayfield education & Research structure is funding numerous an easy science research projects that development our understanding about how nerve cell work, grow, die, and repair themselves.