Oblique view of cervical vertebra : The parts of a human vertebra. Four articular processes originate from the joint between the pedicles and laminae, two point superiorly and two point inferiorly. They interact with the zyhapophysis, a socket for the articular processes, of the adjacent vertebrae to make the spine more stable and to facilitate a small degree of articulation. A single spinous process projects backwards and downwards from the center of the vertebral arch and it serves as a major attachment point for muscles and ligaments of the back.
The two transverse processes project laterally from the join between the pedicle and lamina and also serve as an attachment point for muscles and ligaments of the back. The transverse processes articulate with the ribs in conjunction with the vertebral body. The vertebrae of the spinal column are divided into five regions: cervical, thoracic, lumbar, sacral, and coccyx. The vertebrae comprising the spinal column can be divided into five regions, based on the five varying curvatures of the spine.
The upper three regions of the spinal column are termed the cervical, thoracic, and lumbar; they contain individually jointed vertebrae. The two lower regions—the sacrum and coccyx, or tailbone—are formed from fused vertebrae.
Vertebrae are given an alphanumeric descriptor, with the initial letter derived from the region they are located in followed by a digit that increases moving down the region. For example, the most superior cervical vertebrae is termed C1 and the most inferior C7, which is then followed by the T1 vertebrae of the thoracic region. The cervical region of the spine is the most superior and contains seven small vertebrae. The main function of the cervical region is to facilitate attachment of the skull to the spine, protect the spinal cord over the exposed neck and shoulder region, and support the body.
Cervical vertebra, lateral view : The lateral view of a typical cervical vertebra. The twelve thoracic vertebrae are located inferiorly to the cervical region. They are larger than the cervical vertebrae and increase in size moving inferiorly to the lumbar region. Thoracic vertebra : Image of a typical thoracic vertebra. The five lumbar vertebrae are the largest vertebral bones and increase in size when moving inferiorly. The lumbar vertebrae play a key role in supporting the body and facilitating locomotion.
During childhood the five vertebrae of the sacral region are distinct. In adulthood the five bones fuse to form the sacrum, although it is still often divided into regions termed S1—S5 based on the formation of the original individual bones. The sacrum functions to support the body and protect organs of the pelvis and lower back. 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. It runs from the brainstem to the 1st lumbar vertebra protected within the spinal canal. At the end of the spinal cord, the cord fibers separate into the cauda equina and continue down through the spinal canal to your tailbone before branching off to your legs and feet.
The spinal column also allows for upright posture, protection of the spinal cord and shock absorption. The spinal column and vertebrae are made of different elements, all of which protect the spinal cord while communicating with the brain. These elements also provide sensations through the body via a complex interaction of the bones, ligaments and muscle structures of the back and the nerves that surround it.
The spine is composed of 33 bones, called vertebrae, divided into five sections: the cervical, thoracic, and lumbar spine sections, and the sacrum and coccyx bones. The cervical section of the spine is made up of the top seven vertebrae in the spine, C1 to C7, and is connected to the base of the skull. The top two vertebrae are also know as the atlas and axis, which form the joint for connecting the skull to the spine.
The cervical section is responsible for mobility and normal functioning of the neck, as well as protection of the spinal cord, arteries and nerves that travel from the brain to the body.
The thoracic section of the spine is located at chest level, between the cervical and lumbar vertebrae. The vertebrae in this section are labeled T1 to T12 and serve as attachments for the rib cage. The lumbar section is located between the thoracic vertebrae and the sacrum. The five lumbar vertebrae, labeled L1 to L5, are the main weight-bearing section of the spinal column. The sacrum is the section located at the base of the spine. It does not have discs separating the vertebrae, because its five levels, S1 to S5, are fused together.
The pelvis is connected to the spinal column at the sacrum section. The coccyx is at the very base of the spinal column and is made of four vertebrae that are fused together. The spine is normally a straight line when viewed from the back. If the spine curves to one side or the other, this indicates a condition named scoliosis.
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.
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