A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral column. These are grouped into the corresponding cervical, thoracic, lumbar, sacral and coccygeal regions of the spine. There are eight pairs of cervical nerves, twelve pairs of thoracic nerves, five pairs of lumbar nerves, five pairs of sacral nerves, and one pair of coccygeal nerves. The spinal nerves are part of the peripheral nervous system.
In anatomy, the epidural space is the potential space between the dura mater and vertebrae (spine).
Spondylosis is the degeneration of the vertebral column from any cause. In the more narrow sense it refers to spinal osteoarthritis, the age-related degeneration of the spinal column, which is the most common cause of spondylosis. The degenerative process in osteoarthritis chiefly affects the vertebral bodies, the neural foramina and the facet joints. If severe, it may cause pressure on the spinal cord or nerve roots with subsequent sensory or motor disturbances, such as pain, paresthesia, imbalance, and muscle weakness in the limbs.
Neuromeres are distinct groups of neural crest cells, forming segments in the neural tube of the early embryonic development of the brain. There are three classes of neuromeres in the central nervous system – prosomeres, mesomeres and rhombomeres that will develop the forebrain, midbrain, and hindbrain respectively.
In tetrapods, cervical vertebrae are the vertebrae of the neck, immediately below the skull. Truncal vertebrae lie caudal of cervical vertebrae. In sauropsid species, the cervical vertebrae bear cervical ribs. In lizards and saurischian dinosaurs, the cervical ribs are large; in birds, they are small and completely fused to the vertebrae. The vertebral transverse processes of mammals are homologous to the cervical ribs of other amniotes. Most mammals have seven cervical vertebrae, with the only three known exceptions being the manatee with six, the two-toed sloth with five or six, and the three-toed sloth with nine.
Degenerative disc disease (DDD) is a medical condition typically brought on by the normal aging process in which there are anatomic changes and possibly a loss of function of one or more intervertebral discs of the spine. DDD can take place with or without symptoms, but is typically identified once symptoms arise. The root cause is thought to be loss of soluble proteins within the fluid contained in the disc with resultant reduction of the oncotic pressure, which in turn causes loss of fluid volume. Normal downward forces cause the affected disc to lose height, and the distance between vertebrae is reduced. The anulus fibrosus, the tough outer layers of a disc, also weakens. This loss of height causes laxity of the longitudinal ligaments, which may allow anterior, posterior, or lateral shifting of the vertebral bodies, causing facet joint malalignment and arthritis; scoliosis; cervical hyperlordosis; thoracic hyperkyphosis; lumbar hyperlordosis; narrowing of the space available for the spinal tract within the vertebra ; or narrowing of the space through which a spinal nerve exits with resultant inflammation and impingement of a spinal nerve, causing a radiculopathy.
The filum terminale is a delicate strand of fibrous tissue, about 20 cm in length, extending inferior-ward from the apex of the conus medullaris to attach onto the coccyx. The filum terminale acts to anchor the spinal cord and spinal meninges inferiorly.
The vertebral arteries are major arteries of the neck. Typically, the vertebral arteries originate from the subclavian arteries. Each vessel courses superiorly along each side of the neck, merging within the skull to form the single, midline basilar artery. As the supplying component of the vertebrobasilar vascular system, the vertebral arteries supply blood to the upper spinal cord, brainstem, cerebellum, and posterior part of brain.
The anterior longitudinal ligament is a ligament that extends across the anterior/ventral aspect of the vertebral bodies and intervertebral discs the spine.
The ligamenta flava are a series of ligaments that connect the ventral parts of the laminae of adjacent vertebrae. They help to preserve upright posture, preventing hyperflexion, and ensuring that the vertebral column straightens after flexion. Hypertrophy can cause spinal stenosis.
The intervertebral foramen is an opening between two pedicles of adjacent vertebra in the articulated spine. Each intervertebral foramen gives passage to a spinal nerve and spinal blood vessels, and lodges a posterior (dorsal) root ganglion. Cervical, thoracic, and lumbar vertebrae all have intervertebral foramina.
The posterior longitudinal ligament is a ligament connecting the posterior surfaces of the vertebral bodies of all of the vertebrae of humans. It weakly prevents hyperflexion of the vertebral column. It also prevents posterior spinal disc herniation, although problems with the ligament can cause it.
The posterior spinal artery arises from the vertebral artery in 25% of humans or the posterior inferior cerebellar artery in 75% of humans, adjacent to the medulla oblongata. It is usually double, and spans the length of the spinal cord. It supplies the grey and white posterior columns of the spinal cord.
The internal vertebral venous plexuses lie within the vertebral canal in the epidural space, embedded within epidural fat. They receive tributaries from bones, red bone marrow, and spinal cord. They are arranged into four interconnected, vertically oriented vessels - two situated anteriorly, and two posteriorly:
The posterior atlantooccipital membrane is a broad but thin membrane extending between the to the posterior margin of the foramen magnum above, and posterior arch of atlas below. It forms the floor of the suboccipital triangle.
Segmental medullary arteries are arteries of varying size in the thoracolumbar region that arise from segmental arteries of this region and pass through intervertebral foramina to supply the spinal cord. They may join the anterior spinal artery.
The following outline is provided as an overview of and topical guide to human anatomy:
The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal cord is hollow and contains a structure called central canal, which contains cerebrospinal fluid. The spinal cord is also covered by meninges and enclosed by the neural arches. Together, the brain and spinal cord make up the central nervous system.
The vertebral column, also known as the backbone or spine, is the core part of the axial skeleton in vertebrate animals. The vertebral column is the defining characteristic of vertebrate endoskeleton in which the notochord found in all chordates has been replaced by a segmented series of mineralized irregular bones called vertebrae, separated by fibrocartilaginous intervertebral discs. The dorsal portion of the vertebral column houses the spinal canal, a cavity formed by alignment of the neural arches that encloses and protects the spinal cord.
Each vertebra is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal segment and the particular species.
