For purposes of description, the sympathetic system is divided into cephalic, cervical, dorsal, lumbar and sacral parts.
Cephalic part
- The Cephalic part consists of postganglionic distribution from the superior cervical ganglion.
- The ganglion is situated below the wing of atlas and is an elongated reddish fusiform body.
- The preganglionic fibres arise from the first four thoracic segments of a spinal cord and reach the ganglion by the cervical sympathetic trunk.
- The postganglionic fibres from this ganglion supply gray rami to first cervical spinal and last four cranial nerves and branches also accompany common carotid artery and its branches to supply the structures of the head.
Cervical part
- The cervical part of the sympathetic system consists of the superior and inferior cervical ganglia, connected by an intervening cord on either side.
- The superior cervical ganglion is connected to the last four cranial nerves and first cervical spinal nerve by gray rami. From this ganglion fibres arise which with those of the vagus and glossopharyngeal form a plexus to supply the wall of the pharynx.
- The intermediate cord is the cervical trunk, which passes in close relation to the vagus, runs down the jugular furrow to the thoracic inlet where it separates itself from the vagus and joins the inferior cervical ganglion. The trunk has no connections.
- The inferior cervical ganglion is placed on the internal face of the costal insertion of the scalenus ventralis and against the longus colli.
- It is usually flattened and united with the first thoracic ganglion to form the stellate ganglion. This ganglion receives the cervical trunk and detaches anteriorly the nervous transversarius that accompanies the vertebral artery.
- This nerve passes through the canalis transversarius and detaches at each intervertebral foramen a gray ramus to the cervical spinal nerves from the second to the seventh. Behind, the ganglion detaches a gray ramus to the eighth cervical and the first dorsal spinal nerves.
- It detaches two or three cardiac branches which with the vagus form a cardiac plexus.
Dorsal part
- The dorsal part of the sympathetic system consists of thirteen pairs of ganglia on either side connected by a cord that extends from the inferior cervical ganglion to the first lumbar ganglion. This cord is covered by costal pleura. Each ganglion is connected to the spinal nerve by a gray ramus and a white ramus.
- The first four thoracic ganglia supply
- Aortic branches
- Cardiac branches
- Pulmonary branches and
- Oesophageal branches
- These unite with the respective fibres of the vagus form plexuses and supply the viscera.
- The great splanchnic nerve is formed by branches arising from thoracic ganglion to the thirteenth spinal nerve.
- It extends alongside the vertebral column in close relation to the dorsal sympathetic trunk, passes backward between the crura of the diaphragm and the psoas minor enters the abdomen and joins the coeliacomesenteric ganglia.
- The lesser splanchnic nerve is represented by fibres from the lumbar ganglion which joins the coeliac ganglion and adrenal plexus.
- The abdominal or lumbar part lies along the internal border of the psoas minor above the aorta and vena cava and presents six lumbar ganglia that are connected by rami communicants to spinal nerves.
- They supply branches to aortic and pelvic plexuses.
- The following are the collateral ganglia
- Placed on the coeliac axis is the coeliac ganglion and on the anterior mesenteric artery is the anterior mesenteric ganglion.
- The two ganglia are connected with each other and with those of the opposite side to form a network or plexus around the arteries.
- The coeliac plexus is on the walls of the coeliac artery and its divisions supply the viscera by passing along the divisions of the artery and by forming subsidiary plexuses as gastric plexus, hepatic plexus, splenic plexus and pancreatic plexus. It also gives branches to aortic plexus.
- The anterior mesenteric ganglion is on the walls of the artery of the same name and postganglionic fibers from it follow its divisions to supply subsidiary plexuses to the different parts of the intestine, except terminal colon and rectum and kidney.
- The posterior mesenteric ganglion is an unpaired ganglion.
- It receives fibers from the anterior mesenteric ganglion, last three or four lumbar ganglia and supplies branches to form secondary plexuses to supply rectum. It also gives branches to renal plexus, spermatic or ovarian plexus and pelvic plexus.
- The pelvic or sacral part extends along the inferior face of the sacrum and consists of five pairs of ganglia.
- The pelvic plexuses are formed by branches from the lumbar and sacral ganglia and from posterior mesenteric ganglion. From here secondary plexuses are derived to supply rectum, bladder, uterus, vagina, accessory genital glands and cavernous tissue of penis or clitoris.
- The sacral parts of the two sympathetic trunks unite behind, below the last sacral segment to form the ganglion impar that is continued by the coccygeal nerve that accompanies the middle coccygeal artery.
