The sympathetic system in the Thorax. The autonomic nervous system is a division of the peripheral nervous system regulating the involuntary/unconsciously systems in the body eg breathing, heart beat , digestion etc by innervating visceral organs eg heart, stomach, gland, and intestines. It consists of the sympathetic and the parasympathetic divisions both using similar nerve pathways but generally having antagonistic effects on target tissues. The sympathetic system has a thoracolumbar outflow. The thoracic sympathetic system consists of the sympathetic chain and the ganglia (about 12) lying posterior to the costovertebrea pleura. There 12 ganglia; the stellate or cervicothoracic is the ganglion of the first thoracic vertebrae. It is usually fused with the last cervical vertebrae ganglion. The first nine thoracic ganglia lie anterior to the neck of the ribs while the last three lie lateral to the body of the vertebrae body. The preganglionic neuron – arises in the anterior ramus of the corresponding spinal nerve (T1 to L1 or L2 -the lower limit varies) to relay in the ganglion. The preganglionic neuron can travel up and down the sympathetic chain to synapse in adjacent ganglia or synapse in the ganglion that it enters. The postganglionic neuron leaves the ganglion by way of the gray communicating ramus usually medial to the white ramus of the preganglionic to re-enter the thoracic nerve. Postganglionic neurons travel peripherally to act on smooth muscles, cardiac muscles and glands of the heart, lungs, trachea, oesophagus, thoracic aorta and its branches. The postganglionic neurons from the stellate ganglion and ganglia T2-T4 enter the cardiac plexus regulating the heart. The splanchnic nerves from the 5th to the 12th ganglia are mainly preganglionic fibres which pierce the diaphragm to the abdomen. The greater splanchnic nerve are from the 5th-9th ganglia; lesser splanchnic nerve from the 10th and 11th ganglia and the least splanchnic nerve from the 12th ganglion. Clinical Hyperhydrosis Raynauld’s syndrome- Sympathectomy-different levels - approaches-axillary, cervical, thoracoscopy, thoracotomy Stellate sparing upper thoracic gangliectomy to avoid Horner’s syndrome.
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