It is closely adhered to the spinal cord and the individual nerve roots.
It is highly vascular and gives blood supplies to the neurological structures [ 1 ], [ 3 ], and [ 13 ]. Topography There are 31 pairs of spinal nerves: 8 cervical, 12 thoracic, 5 lumbar, 6 sacrococcygeal.
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The first cervical nerve root exits between the skull C0 and C1. The 8th cervical nerve root exits between C7 and T1. Thereafter, all nerve roots exit at the same level as the corresponding vertebrae. For example, the L1 nerve root exits between L1 and L2. The nerve roots emerge from the spinal cord higher than their actual exit through the intervertebral foramen.
This means that the spinal nerves must often pass downwards adjacent to the spinal cord before exiting through the intervertebral foramen. This leaves the nerves exposed to risk of compression by protruding disc material.
Received Aug 30; Accepted Nov 5.
Therefore, it is possible to have a compression of the L5 nerve root at the L4-L5 disc space. Each spinal nerve root has both motor nerves and sensory nerves. Motor nerves conduct information and orders from the brain to the peripheral nervous system to excite a muscular contraction.
Sensory nerves receive information from the periphery skin, fasciae, tendons, ligaments, muscles and send the information towards the brain.
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Motor fibers are located on the anterior aspect of the spinal cord. Multiple filaments of motor fibers are called ventral roots or anterior roots. The cell bodies or control centers of the motor nerve roots are located within the spinal cord.
Damage or injury to the anterior roots or motor cell bodies may result in the loss of musculoskeletal function. Sensory fibers are located on the posterior aspect of the spinal cord. Each collection of sensory fibers is called a dorsal root or posterior root. The sensory nerves have a special accumulation of cell bodies called the dorsal root ganglia. The ganglia are the control centers of the sensory nerves and are located outside but close to the spinal cord.
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Just beyond the ganglia, the anterior and posterior roots become joined in a common dural sheath. It is at this point that the peripheral nerve is formed [ 4 ], [ 11 ]. Vascularization and innervations The spinal column receives segmental arterial vascularization from the adjacent vessels: for the lumbar region from lumbar and iliolumbar arteries and for the pelvic region from lateral sacral arteries.
All these branches anastomozes and give anterior and posterior spinal arteries that irrigate the marrow.
It is interesting that the intervertebral disc is a poorly vascularized structure. It receives nutrition by passive diffusion through the central vertebral endplates.
The vascularisation of the vertebral body is different in its structure. The most poorly vascularized region is adjacent to the disc. As we approach the central area it becomes more vascularized. The central region can be divided into a nutritive artery vascularized area and a metafizeal arteries vascularized area.
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The peripheric region is vascularized by short peripherial arteries. Oxygenation and metabilic feeding of the disc is regional and determines the lamelae and fibrous ring arrangement. Fluid located between the blades is channeled vertically.
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Frequent movement of blades may increase the diffusion. One of the aging concequences is arterial occlusion and diminished blood flow. Diminished blood flow at the delicate lombar arteries, especially at the fifth pair, through aging and occlusion by dsc compresion, explains the degenerative pathology of the L5 disc.
The veins form communicative plexuses all along the spine. The plexuses drain in the lumbar and the lateral sacral veins. The internal vertebral plexuses form a continuous network between the dura mater and the vertebral canal walls.
Two anterior branches, one on each side of the posterior longitudinal ligament make an anastomosis in front of the ligament and receive the bazivertebral vein. They are interconnected with the basilar and occipital sinuses.
Internal posterior plexuses merge lamella and the yellow ligaments level. There are anterior and posterior communications between the internal and external plexuses. Because of the azygos system, patient positioning is very important in posterior lumbar spine surgery. An increase in pressure will diminish flow through the azygos system and the vena cava.
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Furthermore, increased bleeding makes it difficult to visualize the spinal cord, nerve roots, and disc during surgery. However, these vessels are difficult to identify and cauterize, Centrele anti-îmbătrânire ale Connecticut Review when there is no increased abdominal pressure.
Innervation of the intervertebral disc, ligament structures and fibrous connective tissue of the spinal canal, has Centrele anti-îmbătrânire ale Connecticut Review clinical importance. It is provided by a recurrent nerve, the sinuvertebral nerve.
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In many ways it can be considered equivalent to the recurrent meningeal branch of the cranial nerves. It has dual origin from spinal nerves and sympathetic system. The spinal part arises distal to the dorsal root ganglion and reenter the spinal canal reaching back into the median, then gives rise to discal branches, for the disc above and below.
At the same time innervates the medial facet of te interapofizar joint capsule. C and A-δ fibers are involved in pain transmission, these structures explains the pain caused by compression of the anterior and posterior nerve fibers on the periphery of the ring [ 1 ],[ 4 ],[ 13 ]. Important anatomical related structures It should be noted that the spinal cord ends at the disc between L1 - L2.
Below this level is cauda equina horse tailcovered by meninges to the S2. Anterior to the lombar vertebrae are the large abdominal vessels — the aorta and vena cava.
The aorta bifurcates into the common iliac arteries at L4 level.
Here also the origins of the middle sacral artery and branches of the iliolumbar artery from the internal iliac artery. These arteries irrigate L5 and the sacrococcygeal area. Figure 8.