Spinal nerves aremetamorphosed, paired nerve trunks. The number of spinal nerves, or rather their pairs, corresponds to the number of pairs of segments of the spinal cord and is equal to thirty-one: eight pairs of cervical nerves, twelve pairs of pectorals, five lumbar spines, five phalanges and one pair of coccygeal nerves. With their help, the brain spinal column analyzes the condition and exercises control of the trunk, pelvis, extremities, internal organs of the abdominal and thoracic cavity.
По своему происхождению спинномозговые нервы correspond to a certain part of the body, that is, the part of the skin that developed from some somite - the derivative of dermatosis, from the myotome - the muscle, from the sclerotome - the bone, is innervated. Each nerve originates from the "personal" intervertebral foramen, while it forms from the connecting (in the trunk of the anterior (motor) and back (sensitive) roots.
The spinal nerves reach a length of only one and a half centimeters, at the end they all branch out in the same manner on the posterior and anterior shell branches.
The posterior branch extends between the vertebrae andtransverse processes of the pair into the back region, where it contributes to the innervation of the deep muscles (extend the trunk) and the skin. The spinal nerves of the posterior branches return back between the transverse vertebrae, in particular between their processes, and bend over their articular processes. Excluding the first cervical, as well as the fourth, fifth coccygeal and sacral, the vertebrae are divided into ramus medialis and lateralis, which supply the back surface of the skin of the neck and back, the nape, deep dorsal muscles.
In addition to this, spinal nervestwo branches: connective - to the sympathetic trunk (for innervation of vessels and internals), and the returning branch - going to the intervertebral foramen (for innervation of the spinal cord membranes).
Plexus of the spinal nerves of the anterior branchesare more complex and innervate the skin and muscles of the ventral wall of the trunk and both pairs of extremities. Since in its lower part the abdominal skin takes an active part in the formation of the external genital organs, the skin that covers them is also innervated by the anterior branches. Except for the first two, the last branches are much larger than the rear branches.
Plexus of the spinal nerves of the anterior branches inIts original meto-dimensional structure is preserved only in the thoracic department. In other departments, which are associated with the limbs (in the development of which segmentation is lost), the fibers that depart from the spinal anterior branches are intertwined. Thus, the formation of nerve plexuses (plexus) occurs, where the interchange of fibers of various neuromers occurs. In these plexuses, a large number of spinal nerves participate in a very complex process in which the fibers are redistributed: the peripheral nerves are received from the anterior branches of each spinal nerve fiber, which means the fact that each peripheral nerve contains fibers from many segments of the spinal cord.
Plexuses differ in three types: lumbosacral, brachial and cervical. Lumbosacral, in turn, is divided into coccygeal, sacral and lumbar.
From the above, it should be concluded thatdefeat and damage to some nerve does not entail a violation of the functional of all muscles that receive innervation from the segments giving rise to this nerve. The spinal nerves emerging from the plexus are mixed, so that the picture of nerve damage consists of disorders of sensitivity, vegetative disorders, as well as motor disorders.
