Pelvic splanchnic nerve :
Pelvic splanchnic nerves is also known as nervi erigentes
Pelvic splanchnic nerves are splanchnic nerves that
arise from sacral spinal nerves S2, S3, S4 to provide parasympathetic innervation to the hindgut.
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The splanchnic nerves are paired visceral nerves (nerves that contribute to
the innervation of the internal organs, carrying fibers of the autonomic
nervous system (visceral efferent fibers) as well
as sensory fibers from the organs (visceral afferent
fibers. All carry sympathetic fibers except for the pelvic
splanchnic nerves, which carry parasympathetic fibers.
The parasympathetic
nervous system is referred to as the craniosacral outflow;
the pelvic
splanchnic nerves are the sacral component.
They are in the
same region as the sacral splanchnic nerves,
which arise from
the sympathetic trunk and provide sympathetic efferent fibers.
Splanchnic nerve carrying sympathetic
fibres
·
Cardiopulmonary nerves
·
Thoracic splanchnic nerves (greater,
lesser, and least)
·
Lumbar splanchnic nerves
·
Sacral splanchnic nerves
Splanchnic
nerve carrying parasympathetic fibres
·
Pelvic splanchnic
nerve
Plexuses and pelvic splanchnic nerves :
1.
Sacral plexus
2.
Inferior hypgastric
plexus
3.
Superior hypogastric
plexuses
4.
Inferior mesenteric
plexuses
·
Formation of Pelvic splanchnic nerves
The pelvic splanchnic nerves arise from the anterior rami of the
sacral spinal nerves S2-S4
and enter the sacral plexus. They travel to their side's corresponding inferior
hypogastric plexus, located bilaterally on the
walls of the rectum.
Functional component of
pelvic splanchnic nerve :
1.
GVA:
general visceral afferent : collect sensation from pelvic viscera and hindgut
2.
GVE:
general visceral efferent : innervate smooth muscle cells and gland
Distribution of
1.
GVA:
general visceral afferent: location of cell body in dorsal root ganglia of 2-4
sacral spinal nerve . central process enter the cord by posterior nerve root .
Two fates of GVA fibres :
i.
some
GVA fibres make local synaptic connections .
they are responsible for bladder reflexes
ii.
Other
GVA fibres collect sensory information
from pelvic viscera and convey these information to higher cortical center .
SN: both sympathetic and
parasympathetic pathway collect pain sensation from urinary bladder and rectum
2.
GVE: general visceral efferent
Pre-ganglionic fibres arises
from pre-ganglionic neurons which are located in the 2-4 sacral segments of
spinal cord
Then pre-ganglionic fibres leave the spinal cord through
anterior root of spinal nerve, trunk of spinal nerve then leave the spinal
nerve when they exit anterior sacral foramina and form pelvic splanchnic nerves . The
preganglionic fibres of pelvic splanchnic nerves synapse with Intrinsic
ganglia of descending and sigmoid colon, rectum and
other the pelvic viscera
these fibres innervate
smooth muscles of hindgut and urinary bladder
Three distribution of pelvic splanchnic
nerve
1.
Anterolateral branch
2.
Branches join with hypogastric nerves
3.
Superolateral branch
Distribution of three branches
1.
Anterolateral branch : join with inferior hypogastric
plexuses and then distributed into pelvic viscera
2.
Branches join with hypogastric nerves: after joining with
the hypogastric nerve these branch ascend and join with superior hypogastric
plexuses and distributed in to the inferior mesenteric artery
3.
Superolateral branch : it passes directly into the
tissue of the retroperitoneum and the mesentery of sigmoid and descending colon
Functions of pelvic splanchnic nerve :
1. Pelvic splanchnic nerve the innervation of smooth muscle cells of the pelvic and genital organs.
2.
It relaxes the smooth muscle cells of sphincter vesicae but contract
detrusor muscle (smooth muscle cells) of urinary bladder
3.
It influences motility in the rectum
4.
In the distal 1/3 of the transverse colon, and through the
sigmoid and rectum, and the cervix in females,
5.
The pelvic splanchnic nerves collect the sensation of pain
from the hindgut & pelvic organ but the rest of the proximal gastrointestinal
tract sensation is collected by
the vagus nerve .
6. Vasodilator fibres to the erectile tissue
of the penis and clitoris
7. Secretomotor fibres to the hindgut
