Sacral Plexus, Pelvic Diaphragm

Gross Anatomy


Sacral Plexus, Pelvic Diaphragm


Anatomy Tables for Today's Topic

Muscles
Nerves
Lymphatics

Muscles

Muscle Origin Insertion Action Innervation Artery Notes
coccygeus ischial spine side of the coccyx and lower sacrum elevates the pelvic floor branches of the ventral primary rami of spinal nerves S3-S4 inferior gluteal a. coccygeus and levator ani combined form the pelvic diaphragm
iliococcygeus arcus tendineus levator ani and the ischial spine anococcygeal raphe and the coccyx elevates the pelvic floor branches of the ventral primary rami of spinal nerves S3-S4 inferior gluteal a. the combination of puborectalis, pubococcygeus and iliococcygeus is called the levator ani m.
levator ani posterior surface of the body of the pubis, fascia of the obturator internus m. (arcus tendineus levator ani), ischial spine anococcygeal raphe and coccyx elevates the pelvic floor branches of the ventral primary rami of spinal nerves S3-S4 inferior gluteal a. the combination of puborectalis, pubococcygeus & iliococcygeus is the levator ani m.; coccygeus and levator ani combined form the pelvic diaphragm
obturator internus the internal surface of the obturator membrane and margin of the obturator foramen greater trochanter on its medial surface above the trochanteric fossa laterally rotates and abducts the thigh nerve to the obturator internus m. obturator a. the obturator internus m. leaves the pelvis by passing through the lesser sciatic foramen; the superior and inferior gemellus mm. insert on the obturator internus tendon
piriformis anterior surface of sacrum upper border of greater trochanter of femur laterally rotates and abducts thigh ventral rami of S1-S2   piriformis leaves the pelvis by passing through the greater sciatic foramen
pubococcygeus posterior aspect of the superior pubic ramis coccyx elevates the pelvic floor branches of the ventral primary rami of spinal nerves S3-S4 inferior gluteal a. the combination of puborectalis, pubococcygeus and iliococcygeus is called the levator ani m.
puborectalis posterior aspect of the body of the pubis unites with the puborectalis m. of other side posterior to the rectum draws the distal rectum forward and superiorly; aids in voluntary retention of feces branches of the ventral primary rami of spinal nerves S3-S4 inferior gluteal a. the combination of puborectalis, pubococcygeus and iliococcygeus is called the levator ani m.
pubovaginalis posterior aspect of the body of the pubis fascia of the vagina and perineal body draws the vagina forward and superiorly branches of the ventral primary rami of spinal nerves S3-S4 inferior gluteal a. pubovaginalis is part of the levator ani muscle

Nerves

Nerve Source Branches Motor Sensory Notes
coccygeus m., n. to sacral plexus (brs. of the ventral primary rami of spinal nerves S3-S4) no named branches coccygeus m., levator ani m. none nerve to coccygeus enters the muscle on its pelvic surface
hypogastric n. superior hypogastric plexus inferior hypogastric plexus supplies vascular smooth muscle of the pelvic viscera pain from the pelvic viscera paired; hypogastric n. lies inferior to the common iliac vessels; it contains postganglionic sympathetic axons
hypogastric plexus, inferior hypogastric nn. and sacral splanchnic nn. (postganglionic sympathetic axons); pelvic splanchnic nn. (preganglionic parasympathetic axons from the ventral primary rami of spinal nerves S2-S4) contributes branches to: uterine/vaginal plexus, vesical plexus, prostatic plexus sympathetic: supplies vascular smooth muscle of vessels supplying the pelvic viscera; parasympathetic: supplies smooth muscle of the pelvic viscera pain from the pelvic viscera; general visceral afferent from the pelvic viscera inferior hypogastric plexus lies between the pelvic viscera and the pelvic wall
hypogastric plexus, superior intermesenteric plexus and lumbar splanchnic nn. (postganglionic sympathetic axons) hypogastric nn. (right and left) vascular smooth muscle of the pelvic viscera (sympathetic) pain from the pelvic viscera; general visceral afferent from the pelvic viscera superior hypogastric plexus is the continuation of the intermesenteric plexus; it crosses the pelvic brim
pelvic splanchnic n. ventral primary rami of spinal nerves S2-S4 (cell bodies are located in the lateral horn gray of the sacral spinal cord) unnamed branches contribute to the pelvic plexus (inferior hypogastric) plexus smooth muscle and glands of the gut distal to the left colic flexure; smooth muscle and glands of all pelvic viscera none parasympathetic nerves; these contain preganglionic parasympathetic axons
prostatic plexus inferior hypogastric (pelvic) plexus is continuous with the rectal and vesical plexuses sympathetic: vascular smooth muscle of the pelvic viscera, especially the urethra, prostate gland and ejaculatory ducts; parasympathetic: smooth muscle and glands of the pelvic viscera, especially the urethra, prostate gland, and ejaculatory ducts pain from the pelvic viscera listed at left the autonomic nerve plexuses of the pelvis (prostatic, rectal and vesical in the male; rectal and uterovaginal in the female) are in communication with each other
pudendal n. ventral primary rami of spinal nerves S2-S4 (sacral plexus) inferior rectal n., perineal n., dorsal n. of the clitoris/penis its branches supply: external anal sphincter, bulbospongiosus m., ischiocavernosus m., superficial & deep transverse perineus mm., sphincter urethrae m., sphincter urethrovaginalis, compressor urethrae its bhes supply: skin of the anus, posterior scrotum/labium majus, clitoris/penis pudendal n. passes through the pudendal canal formed by fascia on the medial surface of the obturator internus m.
rectal plexus inferior hypogastric (pelvic) plexus, posterior part no named branches sympathetic: vascular smooth muscle of the pelvic viscera, especially the rectum; parasympathetic: smooth muscle and glands of the pelvic viscera, especially the rectum pain and general sensation from the rectum rectal plexus is continuous with the vesical plexus in the male, uterovaginal plexus in the female
sacral splanchnic n. sacral sympathetic ganglia unnamed branches contribute to the pelvic plexus (inferior hypogastric) plexus vascular smooth muscle of the pelvic viscera pain from the pelvic viscera sacral splanchnic nn. contain both preganglionic and postganglionic sympathetic nerve fibers with postganglionic fibers predominating in number
sympathetic chain ganglia preganglionic sympathetic fibers arrive via white rami communicantes of ventral primary rami of spinal nerves T1-L2 postganglionic sympathetic fibers depart via gray rami communicantes to all spinal nn.; internal & external carotid nn.; cervical cardiac brs.; thoracic direct visceral brs.; greater, lesser & least thoracic splanchnic nn.; lumbar splanchnic nn.; sacral splanchnic nn. dilator pupillae, vascular smooth muscle, arrector pili muscles, sweat glands, suprarenal medulla, heart, lungs and gut pain from viscera located lateral to the vertebral bodies in the neck, thorax & abdominopelvic cavity; the ganglia plus their interconnecting fibers are also known as the sympathetic trunk; preganglionic cell bodies are located in the intermediolateral gray matter of spinal cord levels T1-L2
uterovaginal plexus inferior hypogastric plexus continuous with the rectal plexus sympathetic: vascular smooth muscle of the pelvic viscera, especially the uterus, uterine tubes and vagina; parasympathetic: smooth muscle and glands of pelvic viscera, especially uterus, uterine tubes and vagina pain from the pelvic viscera listed at left the uterovaginal plexus is a subsidiary plexus of the inferior hypogastric plexus
vesical plexus inferior hypogastric plexus continuous with the prostatic plexus sympathetic: vascular smooth muscle of the pelvic viscera, especially the urinary bladder, seminal vesicle, ductus deferens and ejaculatory duct; parasympathetic: smooth muscle and glands of the pelvic viscera, especially the urinary bladder, seminal vesicle, ductus deferens and ejaculatory duct pain and general sensation from the bladder, seminal vesicle and ductus deferens vesical plexus is continuous with the other autonomic nerve plexuses in the pelvis and cannot be distinguished from them
posterior femoral cutaneous n. sacral plexus (ventral primary rami of spinal nerves S1-S3) inferior cluneal nn.; perineal br. sympathetic motor innervation to skin skin of the lower buttock & posterior thigh cutaneous nn. carry postganglionic sympathetic axons to skin
gluteal, inferior sacral plexus (ventral primary rami of spinal nerves L5, S1-S2) no named branches gluteus maximus m. none inferior gluteal n. passes through the greater sciatic foramen inferior to the piriformis m.
gluteal, superior sacral plexus (ventral primary rami of spinal nerves L4-L5, S1) superior & inferior brs. gluteus medius m., gluteus minimus m., tensor fasciae latae m. none superior gluteal n. passes through the greater sciatic foramen superior to the piriformis m.
lumbar plexus ventral primary rami of spinal nerves L1-L4 branches of the lumbar plexus: iliohypogastric n., ilioinguinal n., genitofemoral n., lateral femoral cutaneous n., femoral n., obturator n., lumbosacral trunk (considered to be part of sacral plexus), brs. to the psoas major and minor mm., branches to the quadratus lumborum m. muscles of the lower abdominal wall; cremaster m., psoas major and minor mm., quadratus lumborum m., iliacus m.; muscles of the anterior and medial thigh and hip skin of the lower abdominal wall, skin of the anterior scrotum/labium majus, skin of the anterior and medial thigh and lateral hip lumbar plexus is noted for its variable branching pattern of nerves that supply the abdominal wall
lumbosacral plexus ventral primary rami of spinal nerves L4-S4 branches of the lumbosacral plexus: iliohypogastric n., ilioinguinal n., genitofemoral n., lateral femoral cutaneous n., femoral n., obturator n., lumbosacral trunk (considered to be part of sacral plexus), brs. to the psoas major and minor mm., branches to the quadratus lumborum m., superior & inferior gluteal nn., n. to the obturator internus m., n. to the quadratus femoris m., sciatic n., n. to the piriformis m., posterior femoral cutaneous n., pudendal n., n. to the pelvic diaphragm, pelvic splanchnic nn. muscles of the lower abdominal wall; cremaster m., psoas major and minor mm., quadratus lumborum m., iliacus m.; muscles of the anterior and medial thigh and hip, muscles of the pelvic & urogenital diaphragm, posterior hip, posterior thigh, leg and foot skin of the lower abdominal wall, skin of the anterior scrotum/labium majus, skin of the anterior and medial thigh and lateral hip' skin of the perineum, posterior thigh, leg and foot also known as: lumbar & sacral plexuses
lumbosacral trunk part of the ventral primary ramus of L4 united with the ventral primary ramus of L5 no named branches; it contributes to the formation of the sacral plexus muscles of the hip and posterior thigh see sacral plexus the lumbosacral trunk is not considered to be part of the lumbar plexus
obturator n. lumbar plexus (ventral primary rami of spinal nerves L2-L4) anterior and posterior brs. muscles of the medial thigh: adductor longus m., adductor brevis m. and adductor magnus m., gracilis m., obturator externus m. skin of the lower medial thigh obturator n. passes through the obturator canal
obturator internus m., n. to sacral plexus (ventral primary rami of spinal nerves L5-S2 ) n. to the superior gemellus m. obturator internus m., superior gemellus m. none nerve to obturator internus m. crosses the ischial spine and enters the ischioanal fossa by passing through the lesser sciatic foramen
quadratus femoris m., n. to sacral plexus (ventral primary rami of spinal nerves L4-L5, S1) n. to the inferior gemellus m. quadratus femoris m., inferior gemellus m. none nerve to the quadratus femoris m. passes anterior to the obturator internus tendon
sacral plexus lumbosacral trunk (ventral primary rami of spinal nerves L4-L5), ventral primary rami of spinal nerves S1-S4 superior & inferior gluteal nn., n. to obturator internus m., n. to quadratus femoris m., sciatic n., n. to piriformis, posterior femoral cutaneous n., pudendal n., n. to pelvic diaphragm, pelvic splanchnic nn. muscles of the pelvic diaphragm; muscles of the urogenital diaphragm; muscles of the posterior hip, posterior thigh, leg and foot skin of the perineum, posterior thigh, leg and foot (excluding the medial side of the leg and foot) the sacral plexus is often grouped with the lumbar plexus as the "lumbosacral plexus"
sciatic n. sacral plexus (ventral primary rami of spinal nerves L4-L5 and S1-S3) tibial n., common fibular (peroneal) n. semitendinosus m., semimembranosus m., biceps femoris m., ischioconylar part of the adductor magnus m.; its branches supply all muscles of the leg and foot its branches supply the skin of the leg and foot (excluding the medial side of leg & foot) sciatic n. is composed of tibial and common fibular divisions; branches to muscles come from one of the two divisions, so that the sciatic n. is considered to have no direct muscular brs., only 2 terminal brs.

Lymphatics

Structure Location Afferents from Efferents to Regions drained Notes
iliac nodes, common along the common iliac vessels; over the sacral promontory external iliac nodes, internal iliac nodes lumbar (lateral aortic) chain of nodes lower limb; pelvic organs, perineum, lower part of the anterior abdominal wall common iliac nodes are approximately 6 in number
iliac nodes, external along the external iliac vessels superficial inguinal nodes; deep inguinal nodes; inferior epigastric nodes common iliac nodes lower limb; external genitalia; lower part of the anterior abdominal wall external iliac nodes are 8 to 10 in number
iliac nodes, internal along the internal iliac vessels lymphatic vessels from the pelvic viscera common iliac nodes, external iliac nodes pelvis, perineum and gluteal region internal iliac nodes are 4 to 8 in number
inguinal nodes, deep along the medial side of the femoral v. deep to the fascia lata and inguinal ligament superficial inguinal nodes, popliteal nodes external iliac nodes lower limb, external genitalia, lower part of the anterior abdominal wall the deep inguinal node in the femoral canal is called the node (or gland) of Cloquet
inguinal nodes, superficial in the superficial fascia parallel to the inguinal ligament and along the terminal part of the greater saphenous v. lymphatic vessels from the superficial lower limb, superficial abdominal wall, perineum external iliac nodes; deep inguinal nodes lower abdominal wall; external genitalia; superficial parts of the lower limb superficial inguinal nodes are 12-20 in number; they become inflamed during infections of the lower limb; they may become inflamed during infections of the external genitalia
lateral aortic nodes along the inferior vena cava and abdominal aorta from the aortic bifurcation to the aortic hiatus of the diaphragm common iliac nodes; lymphatic vessels from the posterior abdominal wall and viscera efferents form one lumbar trunk on each side lower limb; pelvic organs; perineum; anterior and posterior abdominal wall; kidney; suprarenal gland; respiratory diaphragm also known as: lumbar nodes; the intestinal trunk drains into to the left lumbar trunk; the lumbar trunks unite to form the thoracic duct/cisterna chyli
lumbar nodes along the inferior vena cava and abdominal aorta from the aortic bifurcation to the aortic hiatus of the diaphragm common iliac nodes; lymphatic vessels from the posterior abdominal wall and viscera efferents form one lumbar trunk on each side lower limb; pelvic organs; perineum; anterior and posterior abdominal wall; kidney; suprarenal gland; respiratory diaphragm also known as: lateral aortic nodes; the intestinal trunk drains into to the left lumbar trunk; the lumbar trunks unite to form the thoracic duct/cisterna chyli
lumbar trunk between the lumbar vertebral bodies and inferior vena cava (right) or aorta (left) at the upper end of the lumbar chain of nodes lumbar (lateral aortic) nodes; the intestinal trunk joins the left lumbar trunk thoracic duct/cisterna chyli left lumbar trunk - left side of the body below the respiratory diaphragm, gut; right lumbar trunk - right side of body below the diaphragm lumbar trunks unite to form the lower end of the thoracic duct; an enlargement of the lower end of the thoracic duct (called the cisterna chyli) occurs in about 25% of individuals, and when it is present, the lumbar trunks drain into it

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Some of the material presented in these tables is contained in the book:
MedCharts Anatomy by Thomas R. Gest and Jaye Schlesinger
Published by ILOC, Inc., New York. Copyright 1995.

Content of these tables has been edited for use in this course by Patrick W. Tank, Ph.D.
Copyright 2005, Department of Neurobiology and Developmental Sciences, University of Arkansas for Medical Sciences.

Unauthorized use is prohibited.