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The pelvic girdle is innervated by nerves that come from the sacral plexus, coccygeal plexus, and pelvic autonomic nerves.
The 4th and 5th lumbar spinal nerves form the lumbosacral trunk.
The lumbosacral trunk joins the 1st through 4th sacral nerves as they exit the sacrum to form the sacral plexus.
The sacral plexus runs down on the posterior pelvic wall anterior to the piriformis muscle.
The nerves eminating from the sacral plexus include:
Sciatic nerve: This nerve is formed by the 4th lumbar through 3rd sacral spinal nerves.
The sciatic nerve is the largest nerve in the body.
It leaves the pelvis through the greater sciatic foramen to enter the gluteal area.
Pudendal nerve: This nerve is formed from the 2nd through 4th spinal sacral nerves.
The pudendal nerve exits the pelvis through the greater sciatic foramen and enters the perineum through the lesser sciatic foramen to innervate the muscles and skin of the perineum.
Superior gluteal nerve: Formed by the 4th lumbar through the 1st sacral spinal nerves.
The superior gluteal nerve leaves the greater sciatic foramen to innervate gluteal muscles.
Inferior gluteal nerve: This nerve’s formed by the 5th lumbar through 2nd sacral spinal nerves.
Inferior gluteal nerve runs through the greater sciatic foramen to innervate gluteal muscles.
Nerve to the quadratus femoris muscle: is formed from the 4th lumbar through the 1st sacral spinal nerves.
The Inferior gluteal nerve leaves the greater sciatic foramen to innervate hip muscles.
Nerve to the obturator internus muscle: This nerve is formed by fibers from the 5th lumbar through the 2nd sacral spinal nerves.
The nerve to the obturator internus muscle also leaves the greater sciatic foramen to innervate hip muscles.
Nerve to the piriformis muscle: Originates from the 1st and 2nd sacral spinal nerves.
Perforating cutaneous nerve: This nerve is formed from the 2nd and 3rd sacral spinal nerves and innervates the skin over the lower and medial portion of the buttock.
Posterior femoral cutaneous nerve: This nerve’s formed from the 2nd and 3rd sacral spinal nerves and innervates the skin of the perineum and the back surface of the thigh and leg.
Pelvic splanchnic nerves: Stemming from the 2nd through 4th sacral spinal nerves, these nerves provide the parasympathtetic innervation to the pelvic organs.
The coccygeal plexus of nerve fibers is formed by the 4th and 5th sacral spinal nerves and the coccygeal nerves.
The coccygeal plexus of nerve fibers supplies the coccygeus and levator ani muscles and the sacrococcygeal joint.
Anococcygeal nerves innervate the skin between the coccyx and anus.
The obturator nerve arises from the from the lumbar plexus.
The obturator nerve inner bates the medial thigh.
Pelvic autonomic nerves innervate the pelvic cavity and control blood flow, hormone levels, and bodily functions.
Sacral sympathetic trunks run in front of the sacrum and behind the rectum.
The sacral sympathetic trunks provide postganglionic sympathetic fibers to the sacral plexus that innervate the lower extremities, and provide fibers to the hypogastric plexus.
There is a superior hypogastric plexus: containing sympathetic fibers from the aortic plexus divides into the left and right hypogastric nerves.
Inferior hypogastric plexuses formed when the right and left hypogastric nerves are joined by preganglionic parasympathetic fibers from the pelvic splanchnic nerves.
These plexuses are located on each side of the rectum and the base of the bladder, and contain both sympathetic and parasympathetic fibers.
Pelvic splanchnic nerves (S2–S4): are preganglionic parasympathetic fibers that originate from the 2nd, 3rd, and 4th sacral spinal segments.
Parasympathetic stimulation increases peristalsis and contraction of the bladder and rectum for urination and defecation, sympathetic stimulation inhibits peristalsis and stimulates muscle contraction of genital organs during orgasm.