Editing Retroperitoneum (section)

=== Autonomic nervous system ===
* '''General structure of the autonomic nervous system consists of two nerves with two cell bodies.'''
** '''The pre-ganglionic neuron has a cell body within the central nervous system''' '''and an axon that extends into the peripheral nervous system, synapsing with another neuron within a ganglion.'''
** The second neuron is referred to as a '''post-ganglionic neuron''', and its '''axon enters the structure in which it provides innervation.'''
** '''An exception to this general structure is the adrenal gland where the pre-ganglionic fibers synapse directly with the cells of the adrenal medulla resulting in release of catecholamines'''
* '''Parasympathetic nervous system'''
** '''Pre-ganglionic fibers originate from:'''
*** '''Cranial nerves''' III, VII, IX, and X
**** '''The vagus nerve (cranial nerve X) provides preganglionic parasympathetic fibers to the thoracic, abdominal, and pelvic viscera'''
*** '''Ventral rami of the S2, S2, and S4'''
**** '''The S2-S4 preganglionic fibers form the pelvic splanchnic nerves, which provide parasympathetic innervation to the pelvic and abdominal viscera'''
** '''Post-ganglionic parasympathetic fibers are often within the walls of the viscera'''
* '''Sympathetic nervous system'''
** '''The pre-ganglionic fibers originate from:'''
*** '''T1 to L2''' and exit through the ventral root and course through the corresponding spinal nerve and anterior rami '''into the ipsilateral sympathetic trunk.'''
**** '''The fibers then run medial to the psoas muscle along the anterolateral aspect of the spine. The paired sympathetic trunks are in close proximity to the lumbar arteries and veins, which cross them perpendicularly.'''
** The pre-ganglionic fibers can
**# Synapse within the ganglia of the sympathetic trunk and send forth post-ganglionic fibers to the body wall and lower extremities
**# '''Leave the trunk as splanchnic nerves to synapse with ganglia from one of autonomic plexuses of the aorta (3):'''
**## '''Celiac plexus'''
**##* First and largest of these plexuses
**##* Contains paired ganglia that lie lateral to the celiac artery.
**##* Much of the autonomic innervation to the kidney, adrenal, renal pelvis, and ureter runs through this plexus.
**## '''Superior hypogastric plexus'''
**##* '''Originates at the caudal extent of the abdominal aorta and extends to the anterior surface of the 5th lumbar vertebra.'''
**##** '''Clinical significance: extensive retroperitoneal dissection that causes disruption of these plexuses may result in loss of seminal vesicle emission or failure of bladder neck closure resulting in retrograde ejaculation.'''
**## '''Inferior hypogastric plexus'''
**#*'''Much of the sympathetic innervation to the pelvic viscera travels through the superior and inferior hypogastric plexuses, which are contiguous.'''
* Confusion may arise with the term splanchnic used for nerves of both the parasympathetic and the sympathetic systems. For clarification, the thoracic splanchnics (greater, lesser, and least), lumbar splanchnics, and '''sacral splanchnics carry sympathetic fibers''' from the paired sympathetic trunks to the autonomic plexuses, whereas the '''pelvic splanchnics carry parasympathetic fibers from the sacral outflow'''