Pelvic Nerves

Front 1

Autonomic Nerves of the Pelvis

Back 1

Aortic Plexus
Testicular Plexus
Superior Hypogastric Plexus
Inferior Hypogastric Plexus


Pelvis comes from pelvic splanchnics (S2-S4) (PARA) and sacral splanchnics (SYMP).

Inferior hypogastric gives off vesical plexus, uterovaginal plexus and rectal plexus. (in woman)

It gives off deferential plexus, vesical plexus, prostatic plexus, and rectal plexus (in men).

Front 2

Superior Hypogastric Plexus (SHG plexus)

Back 2

Continuation of aortic plexus.

Receives lower two lumbar splanchnics from sympathetic chain.

Lies behind peritoneum and descends in front of L5.

Bifurcates into right and left hypogastric nerves, which go to inferior hypogastric plexuses (IHGs).

Contains visceral motor (symp/para) and visceral sensory.

Only contains a few motor parasympathetics (S2-S4) which run recurrent course through IHG plexus from pelvic splanchnics.

Front 3

Hypogastric nerve

Back 3

Lateral extension of SHG plexus.

Lies in extraperitoneal connective tissue next to rectum.
Provides branches to sigmoid colon and descending colon.

Joined by the pelvic splanchnic nerves (para) to make the inferior hypogastric plexus (IHG plexus).

Front 4

Inferior Hypogastric Plexus

Back 4

Formed by union of:
- hypogastric
- pelvic splanchnic
- sacral splanchnic

Lies against pelvic wall lateral to rectum, vag, bladder.

Contains:
- visceral motor sympathetic (pre and post ganglionic)
- visceral motor parasymp (pre and post)
- visceral sensory fibers
- pelvic ganglia for synapsing

Gives rise to next wave of plexuses (middle rectal, uterovaginal, vesical, differential, prostatic)

Front 5

Pelvic splanchnic nerves

Back 5

Only para. splanchnic nerves.
Come from S2-S4.
Contribute to pelvic plexus.
Supply descending colon, sigmoid colon, other viscera in pelvis and perineum (including cavernous nerves of penis).

Front 6

Pudendal vs Pelvic Splanchnics

Back 6

Pudendal nerve:
- from S2-S4 (ventral)
- nerve of the perineum
- Somatic motor, general sensory, visceral motor and sensory

Pelvic splanchnics:
- from S2-S4
- visceral motor parasymp.
- Innervate hindgut and pelvic viscera (hollow muscles made of smooth muscle).

Front 7

Innervation of bladder

Back 7

Sympathetic starts at T11-L2, goes down symp. trunk and synapses at vesical plexus. Postgang. goes to bladder.

Parasymp comes from S2-S4 (pelvic splanchnic) and synapses at bladder.

Front 8

Urination (micturition)

Back 8

About 300 ml triggers stretch receptors. Sends visceral sensory impulses to S2-S4.

Visceral motor para. neurons from pelvic splanchnic travel to bladder walls. Detrusor muscle contracts. Cause relaxation of internal sphincter.

Somatic motor of PUDENDAL nerve (S2-S4) causes relaxation of external (voluntary) sphincter. Abd. muscles can help.

Front 9

Innervation of Testis

Back 9

Symp comes from T10-T11. Synapses in testicular plexus, postgang goes to testes.

Parasymp comes from vagus, synapses at testes.

Front 10

Innervation of male reproductive organs (ductus deferens, seminal vesicles, ejaculatory ducts, prostate)

Back 10

Symp. comes from T10-L2, synapses at pelvic plexus (or others) and postgang. goes to organs.

Parasymp comes from pelvic splanch (S2-S4) and synapses at organs.

Front 11

Erection

Back 11

Visceral motor (parasymp.) neurons from pelvic splanchnics (S2-S4) dilate arteries of the erefctile tissue, expanding corpora cavernosa and corpus spongiosum. These nerves are the cavernous nerves.

Veins are compressed, so blood trapped.

Somatic motor from pudendal (S2-S4) contract bulbospongiosus and ischiocavernosus muscles, maintaining erection.

Front 12

Ejaculation

Back 12

Visceral motor (symp) cause contractions of reproductive organs (epididymis, ductus deferens, seminal vessicles, prostate)
Contraction propels semen:
- sperm from testes
- SV secretion (alkaline substance)
- prostate secretion (acid)
- bulbourethral gland secretion (galactose and mucus)

Bulbospongiosus contracts to assist ejaculation.

Internal sphincter of bladder contracts, preventing semen from entering bladder.

Front 13

Innervation of ovary

Back 13

Symp comes from T10/T11, synapses at ovarian plexus.

Parasymp comes from vagus nerve, synapses at ovary.

Front 14

Innervation of female reproductive organs

Back 14

T10-L2 provides symp innervation, synapses at pelvic (and other) plexuses.

Pelvic splanchnic provide parasymp. Synapse at organs.

Front 15

Innervation of rectum

Back 15

L1-L2 provide symp innervation, synapse at inferior mesenteric ganglion.

S2-S4 provide parasymp innervation, synapase at rectum.

Front 16

Defecation

Back 16

Increase in rectal pressure with feces sensed by visceral sensory of S2-S4 and by general sensory of inferior rectal nerve (branch of pudendal, S2-S4).

Voluntary contraction of thoracic and pelvic diaphragms (C3-C5 and pudendal, S2-S4)

Peristalses of colon and rectum by visceral parasymp.

Relaxation of puborectalis muscle, straightening of anorectal junction.

Relaxation of external and internal anal sphincters.