Sometimes a person may have an additional vertebra, which is called a transitional body and is usually found at the sixth level of the lumbar area labeled L6. The bottom of the spine is called the sacrum. It is made up of several vertebral bodies usually fused together as one.
The remaining small bones or ossicles below the sacrum are also fused together and called the tailbone or coccyx. The spine above the sacrum consists of:. The spinal column combines strong bones, unique joints, flexible ligaments and tendons, large muscles and highly sensitive nerves. While many of us take the benefits of a healthy spine for granted, spinal pain is a sharp reminder of how much we depend on our back in daily life. Some causes of spinal pain include:. The spinal column is made up of many parts, all designed to help the back move flexibly, support body weight and protect the spinal cord and nerves.
These parts include the:. Skip to content. Anatomy of the Spine Not what you're looking for? However, the spine does have some normal, gradual curves when viewed from the side. The neck and lumbar sections of the spine have a lordotic curve, which means that they curve inward.
These spinal curves help maintain balance while upright and support the weight of the head and upper body. However, too much curvature may cause spinal imbalance, causing spinal conditions that may result in pain or loss of mobility. Normal adult spines are positioned over the pelvis, so upright posture doesn't strain muscles. However, changes of spinal position can stress muscles and cause spinal deformity. If the spine is injured and unable to function properly, it can be very painful or even disabling.
The spine is made of many parts that protect the spinal cord, facilitate movement and support the body. The spinal cord has nerve pathways that carry signals, such as pain, from the arms, legs, and the body to the brain.
Nerve roots are used to transmit information between the spinal cord and the other parts of the body, such as arms, legs and organs. The flat plates of the lamina create the outer wall of the vertebral canal and help protect the spinal cord.
Discs separate the vertebrae. They are made of tough, elastic material that allows the spine to bend and twist naturally. The spinous process protrudes from the back of each vertebra. Muscles and ligaments that move and stabilize the vertebrae attach to the spinous processes. Two transverse processes stick out of the sides of each vertebra. Muscles and ligaments that move and stabilize the vertebrae attach to the transverse processes. All of the above elements of the spinal column and vertebrae protect the spinal cord, which provides communication to the brain.
The spinal cord also transmits sensation and mobility in the body through interaction of ligaments, bones and muscle structures of the back and its surrounding nerves.
Vertebrae are the 33 individual bones that interlock with each other to form the spinal column. The vertebrae are numbered and divided into regions: cervical, thoracic, lumbar, sacrum, and coccyx Fig. Only the top 24 bones are moveable; the vertebrae of the sacrum and coccyx are fused. The vertebrae in each region have unique features that help them perform their main functions. Cervical neck - the main function of the cervical spine is to support the weight of the head about 10 pounds.
The seven cervical vertebrae are numbered C1 to C7. The neck has the greatest range of motion because of two specialized vertebrae that connect to the skull. The first vertebra C1 is the ring-shaped atlas that connects directly to the skull. The second vertebra C2 is the peg-shaped axis, which has a projection called the odontoid, that the atlas pivots around.
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.
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