Atlas of Human Anatomy by Netter

page 209

Autonomic nerves

Sympathetic innervation

Sympathetic trunks

Contain fibers from lower thoracic and upper lumbar spinal segments

Descend on posterior abdominal wall on either side of the vertebral bodies

Descend behind common iliac artery, in front of sacrum and piriformis muscle

Fuse on anterior surface of coccyx as ganglion impar

Are source of sacral splanchnic nerves that join inferior hypogastric (pelvic) plexus in pelvis

Contain either postsynaptic fibers from synapses in ganglia superiorly or pre- synaptic fibers that will synapse in one of four

sympathetic ganglia in pelvis

Primary function is to send postsynaptic fibers to sacral spinal nerves via grey rami communicantes

No white rami communicantes associated with sacral sympathetic trunks because sympathetic outflow is thoracolumbar

Lumbar splanchnics join superior hypogastric plexus

Superior hypogastric plexus

Is located just below the bifurcation of the aorta

Is a continuation of the intermesenteric/aortic plexus

Contains no parasympathetic fibers

Contains visceral afferents ascending from the pelvis

Continues into the pelvis as loose collections of fibers in either side of the anterior sacrum = right and left hypogastric nerves

Spreads out in pelvis as inferior hypogastric (pelvic) plexus

Functions

Vasomotor, pilomotor, secretory to sweat glands to skin of perineum and lower limb

Controls ejaculation (in males)

Innervates smooth muscle of blood vessels in pelvis and smooth muscle of some organs

Parasympathetic innervation

From pelvic splanchnic nerves

Outflow from 2nd to 4th sacral spinal cord segment

Contain visceral afferents

Controls micturition, erection, and defecation

Innervates descending and sigmoid colon via fibers ascending in the sigmoid mesentery and the parietal peritoneum of the left side

of the posterior abdominal wall

Inferior Hypogastric (Pelvic) Plexus

General structure

Formed from fibers of hypogastric nerves, sacral splanchnic nerves, and pelvic splanchnic nerves

Lies on posterolateral pelvic wall internal to internal iliac arteries and their branches

Gives off

Middle rectal plexus

Uterovaginal plexus (females)

Vesical plexus

Deferential plexus

Prostatic plexus (males

Cavernous nerves (nervi erigentes) to erectile tissue of penis and clitoris

Except for cavernous nerves, nerves in the various plexuses reach the viscera in company with relevant branches of the internal iliac artery

Branches transmit efferents from both sympathetic and parasympathetic nervous systems and visceral afferents

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Contents

Pre- and postsynaptic sympathetic fibers from superior hypogastric plexus via hypogastric nerves

Postsynaptic sympathetic fibers from sacral splanchnic nerves

Sympathetic ganglia

Visceral afferent fibers that either ascend along the hypogastric nerves or return to the CNS via the pelvic splanchnic nerves, depending on

the information carried.

Presynaptic parasympathetic fibers from the pelvic splanchnic nerves

Enteric parasympathetic ganglia where the plexus lies on or near a pelvic viscus

Postsynaptic parasympathetic fibers from the enteric ganglia to the viscus innervated