The cervical spine begins at the base of the skull. Seven vertebrae make up the cervical spine with eight pairs of cervical nerves. The individual cervical vertebrae are abbreviated C1, C2, C3, C4, C5, C6 and C7. The cervical nerves are also abbreviated; C1 through C8.

Cervical Vertebrae and Supporting Structures

The cervical bones - the vertebrae - are smaller in size when compared to other spinal vertebrae. The purpose of the cervical spine is to contain and protect the spinal cord, support the skull, and enable diverse head movement (e.g., rotate side to side, bend forward and backward).
A complex system of ligaments, tendons, and muscles help to support and stabilize the cervical spine. Ligaments work to prevent excessive movement that could result in serious injury. Muscles also help to provide spinal balance and stability, and enable movement. Muscles contract and relax in response to nerve impulses originating in the brain. Some muscles work in pairs or as antagonists. This means when a muscle contracts, the opposing muscle relaxes. There are different types of muscle: forward flexors, lateral flexors, rotators, and extensors

Spinal Cord and Cervical Nerve Roots
Nerve impulses travel to and from the brain through the spinal cord to a specific location by way of the peripheral nervous system (PNS). The PNS is the complex system of nerves that branch off from the spinal nerve roots. These nerves travel outside of the spinal canal or spinal cord into the organs, arms, legs, fingers - throughout the entire body.
Injury or mild trauma to the cervical spine can cause a serious or life-threatening medical emergency (e.g. spinal cord injury or SCI, fracture). Pain, numbness, weakness, and tingling are symptoms that may develop when one or more spinal nerves are injured, irritated, or stretched. The cervical nerves control many bodily functions and sensory activities.

  C1: Head and neck
  C2: Head and neck
  C3: Diaphragm
  C4: Upper body muscles (e.g. Deltoids, Biceps)
  C5: Wrist extensors
  C6: Wrist extensors
  C7: Triceps
  C8: Hands

Lumbar Spine

The lumbar spine - or low back - is the third major region of the spine (Figure 2). Most people have five bones or vertebrae in the lumbar spine, although it is not unusual to have six. Each vertebra is stacked on top of the other and between each vertebra is a gel-like cushion called a disc (intervertebral disc). The discs help to absorb pressure, distribute stress, and keep the vertebrae from grinding against each other.

Intervertebral Discs
Intervertebral discs are found between each vertebra. The discs are flat, round structures about a quarter to three quarters of an inch thick with tough outer rings of tissue called the annulus fibrosis that contain a soft, white, jelly-like center called the nucleus pulposus. Flat, circular plates of cartilage connect to the vertebrae above and below each disc. Intervertebral discs separate the vertebrae, but they act as shock absorbers for the spine. They compress when weight is put on them and spring back when the weight is removed.
Intervertebral discs make up about one-third of the length of the spine and constitute the largest organ in the body without its own blood supply.
The discs receive their blood supply through movement as they soak up nutrients. The discs expand while at rest allowing them to soak up nutrient rich fluid. When this process is inhibited through repetitive movement, injury or poor posture, the discs become thinner and more prone to injury. This may be a cause of the gradual degeneration of the structure and function of the disc over time

Ligaments, Tendons
The vertebrae and discs are held together by groups of ligaments (Figure 3). Ligaments connect bone to bone, where as tendons connect muscle to bone. In the spine, tendons connect muscles to the vertebrae. The ligaments and tendons help to stabilize the spine and guard against excessive movement in any one direction.

Spinal Joints

The spine also has joints - similar to knees, elbows, and other joints. The spinal joints are called facet joints (Figure 4). The facet joints have been described as finger-like and link the vertebrae together. The facet joints are located at the posterior area of the spinal column. In addition, the facet joints help to make the spine flexible.

Nerve Center
In the center of the spinal column is a vertical hole called the spinal canal; it contains the spinal cord. The bones that create the spinal canal serve as armor to help protect the spinal cord from injury. Small nerve roots branch off from the spinal cord through spaces on between each vertebra and extend out into the entire body (Figure 5). The spinal cord and the nerves are part of the central nervous system that includes the brain. The nerves are the body's neural message system.

Figure 6 :
The ventral (motor) and dorsal (sensory) roots join to form the spinal nerve. The spinal cord is covered by three layers of meninges: pia, arachnoid and dura mater.

Spinal Cord

The spinal cord is part of the central nervous system of the human body. It is a vital pathway that conducts electrical signals from the brain to the rest of the body through individual nerve fibers. The spinal cord is a very delicate structure that is derived from the ectodermal neural groove, which eventually closes to form a tube during fetal development. From this neural tube, the entire central nervous system, our brain and spinal cord, eventually develops. Up to the third month of fetal life, the spinal cord is about the same length as the canal. After the third month of development, the growth of the canal outpaces that of the cord. In an adult the lower end of the spinal cord usually ends at approximately the first lumbar vertebra, where it divides into many individual nerve roots (L1).

Spinal Canal
The spinal canal is the anatomic casing for the spinal cord. The bones and ligaments of the spinal column are aligned in such a way to create a canal that provides protection and support for the spinal cord. Several different membranes enclose and nourish the spinal cord and surround the spinal cord itself. The outermost layer is called the "dura mater," which is a Latin term that means "hard mother," indicating that early anatomists had at least a rudimentary sense of humor. The dura is a very tough membrane that encloses the brain and spinal cord and prevents cerebrospinal fluid from leaking out from the central nervous system. The space between the dura and the spinal canal is called the "epidural space". This space is filled with tissue, vessels and large veins. The epidural space is important in the treatment of low-back pain, because it is into this space that medications such as anesthetics and steroids are injected in order to alleviate pain and inflammation of the nerve roots.
Figure 1 :
The five regions of the Spinal Column.
Figure 2 :
While vertebrae have unique regional features , every vertebra has three main parts : body (purple) , vertebral arch (green) , and processes  for muscle attachment ( orange) .

Figure 3:
Discs are made of a gel-filled center called the nucleus and a tough fibrous outer ring called the annulus. The annulus pulls the vertebral bodies together against the resistance of the gel-filled nucleus.


Figure 4 :
The vertebral arch (teal) forms the spinal canal through which the spinal cord runs. Seven bony processes arise from the vertebral arch to form the facet joints and processes for muscle attachment (beige)


Figure 5 :
The superior and inferior facets connect each vertebra together. There are four facet joints associated with each vertebra.

Figure 6 :
The ligamentum flavum, anterior longitudinal ligament (ALL), and posterior longitudinal ligament (PLL) allow the flexion and extension of the spine while keeping the vertebrae in alignment.
Figure 7 :
The ventral (motor) and dorsal (sensory) roots join to form the spinal nerve. The spinal cord is covered by three layers of meninges: pia, arachnoid and dura mater.
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