spinal routes

Question 1

sympathetic supply to the head

Answer 1

supply to the head and CI + C2 regions - preganglionic fibers pass through the cervicothoracic ganglion and travel cranially in the sympathetic trunk (called the vagosympathetic trunk in the neck because the vagus nerve is bound up with it) to eventually synapse with their post ganglionic fibers in the cranial cervical ganglion (fused chain ganglia of C1-C2). Post ganglionic fibers destined for the C1 and C2 via the communicating branch. Post ganglionic fibers destined for the head travel initially along a plexus surrounding the internal carotid artery and are distributed distally along branches of most cranial nerves (except I, II, and VIII) and smaller blood vessels.
This arrangement results in the phenomenon that serious damage to the vagosympathetic trunk in the cervical region will eliminate the pre ganglionic supply to the cranial cervical ganglion and the entire sympathetic supply to the head will essentially be removed. HORNER’S SYNDROME

Question 2

sympathetic supply to the abdominal/pelvic cavities, and the genitalia

Answer 2

• preganglionic CB are located primarily in the alteral horn of T8-L3.
• preganglionic fibers enter the sympathetic trunk run caudally, and either (i) leave the turnk (at caudal thoracic levels) in the thoracic splanchnic nerves which perforate the diaphragm and enter the abdoominal cavity, or (ii), leave the sypathetic trunk the lumbar region (L1-L4) in the lumbar splanchnic nerves.
• these fibers synapse in any of a number of prevertebral (also called collateral or intermediate) ganglia. Examples are the celiacomesenteric, adrenal, aorticorenal, caudal mesenteric ganglia. Post ganglionic fibers travel to their respective effector organ via arterial plexuses.
• preganglionic fibers destined for the pelvic and urogenital organs synapse in the caudal mesenteric ganglion and the postganglionic fibers leave via the hypogastric nerves, pass through the pelvic plexus and supply their assigned effectors via arterial plexuses and small nerve bundles. many preganglioncs destined for the external genitalia synapse in the pelvic plexus or sacral chain ganglia.

Question 3

sympathetic supply to the body wall in the L4-Cd region (including the pelvic limb)

Answer 3

• preganglionic CB are usually located in the lateral horn of the L1-L3 segments and enter the sympathetic trunk to synapse in the chain ganglia of L4-S1
• postganglionic fibers run back to the spinal nerve of that segment via the communicating branch for distribution o the body wall

Question 4

parasympathetic fibers supply to the visceral organs as far distally as the transverse colon

Answer 4

• preganglionic fibers run out of the brain stem in the vagus nerve, descend caudally in the vagosympathetic trunk, pass through the thorax in the dorsal and ventral vagal trunks, and rech the abdominal autonomic plexuses (celiacomesenteric, caudal mesenteric etc.) through which they pass without synapsing. eventually, the preganglionic fibers synapse in a terminal ganglion (eg myenteric plexus) in the effector organ
• postganglionic fibers are very short and run from the terminal ganglion (eg myenteric plexus of gut wall) to the effector)

Question 5

parasympathetic fibers supplying the visceral organs distal to the transverse colon (descending colon, pelvic organs, urogenital tract, and external genitalia)

Answer 5

• preganglionic fibers, with CB in sacral segments S1-S2 in the dog, and S3 - S4 in the horse, travel through pelvic nerve (not the communicating branches), which descends in the pelvic cavity to form the pelvic plexus (a plexus of nerves and small ganglia containing post ganglionic CB)
• most preganglionic synapse here but others pass through to eventually synapse in a terminal ganglion