|Peripheral Nervous System And Rami
The Peripheral Nervous System, or PNS, lies outside the Central Nervous System or CNS. Its function is to connect the CNS to the limbs and other parts of the body. The neurons of the Sympathetic Nervous System are considered to be part of the Peripheral Nervous System.
Rami or Rami Communicans is when a nerve connects two other nerves. There are two types of Rami Communicans, the gray and white Ramus Communicans. The grey ramus connects a spinal nerve to a neighboring ganglion of the sympathetic trunk, while the white rami connect the thoracic and lumbar nerves to the sympathetic ganglion.
White rami are sympathetic fibers like the gray rami but are different for being myelinated and preganglionic. The gray is unmyelinated and postganglionic. The white rami look shiny and white because of myelin sheath. The white rami pass in the opposite direction as that of the gray rami. More specifically, the white rami go to the peripheral branches coming from the lower part of the sympathetic trunk in the thorax. The anterior rami of the nerves are connected to the ganglia of the sympathetic.
The gray rami branches out irregularly from every thoracic ganglion and as mentioned earlier, they go in the reverse direction of the white rami to get connected with the anterior rami of the thoracic nerves.
The peripheral branches also come irregularly from the ganglia and the connecting cord. The rami pulmonales come from the gangliated trunk to join the posterior pulmonary plexus, while the rami aortic come from the upper five thoracic ganglia and joins the thoracic aorta.
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