Pelvic Gross Anatomy

Pelvis – "twin brother of Elvis" – region where the trunk and lower limbs meet; compromised by walking and reproduction

Two major divisions, distinguished based upon location relative to pelvic brim (superior margin of pubic symphysis, pubic crest, pecten pubis, arcuate line of the ilium, anterior border of the ala (wing) of the sacrum, and sacral promontory)

(1) greater pelvis (pelvis major, "false pelvis") – superior to pelvic brim

(2) lesser pelvis (pelvis minor, "true pelvis") – inferior to pelvic brim

Innervation and Blood Supply

Innervation

Pudendal nerve originates from tibial portion of the sacral, from the Lumbo-sacral plexus (S2-S4)

pudendal nerve comes from the great sciatic, turns the corner around the sacrospinous ligament,then immediately goes into the lesser sciatic foramen and straight into the pudendal canal; this is where we find pudendal nerves and vessels

these vessels run over the obturator internus against the lateral wall inside the ischio rectal fossa

the pudendal nerve itself innervates the pelvic floor, then separates into 2 nerves supplying internal and external genitalia

Blood Supply

Pudendal Artery – follows pudendal nerve

Pelvic Floor

keeps guts from falling through pelvis; formed by adapted "tail wagging" muscles

formed by funnel shaped pelvic diaphragm muscles which separate pelvic cavity from the perineum

body wall muscles are voluntary striated muscles, and therefore get innervation from ventral rami

muscles run across the obturator foramen, along internal aspect of the pelvis from the spine of the ischium to the pubis

Composed of two primary muscle groups:

(1) Two Coccygeus muscles (sacro-spinous ligament non functional) – also referred to as ischiococcygeus

(2) Two Levator ani muscles made up of two primary portions – also puborectalis in some books

Pubococcygeus running from the pubis to the coccyx

Illiococcygeus (from illium in tail wagging animals, not us) [ignore books that say there is a ischiococcygeus]

Perineum

diamond-shaped region of trunk between thigh and buttocks inferior to the pelvic diaphragm – see diagram

Boundaries: pubic symphysis, inferior pubic rami, ishial rami, ischial tuberosities, sacrotuberous ligaments

The perineum is divided into two triangles by a line drawn through the Ischium:

(1) Anal triangle – anus exits in center

Levator ani (not shown) forms a sling that starts and ends at pubic symphysis, running around the rectum
part of the pelvic diaphragm, the deepest component of the perineum

divides rectum from anus; constricts when contracted

anococcygeal ligament connect anus to coccyx; is the posterior extension of the superficial external anal sphincter muscle

(2) Urogenital triangle – urogenital system exits in center

urogenital diaphragm – thin striated muscle stretching between pubic arch, superficial to pelvic diaphragm; reinforces urogenital opening not covered by levator ani

made of deep transversus perinei muscles (most posterior and anterior) and sphincter urethra muscle that surrounds urethra (more of an arch in female)
the external anal sphincter is outside the triangle
the central perineal body is where the levator ani and urogenital diaphragm converge

Structures: Bony Landmarks, Ischiorectal Fossa and Anal Triangle

Bones

hip bones – formed by fusion of three bones - Pubis; Ilium; Ischium

Sacrum – formed from five fused sacral vertebrae; transmits weight of body to the pelvic girdle via the sacroiliac joints

Coccyx – formed from fusion of 3-5 vertebrae (rudimentary vertebrae - bodies only)

Fascia and Ligaments

Pubic Symphysis – fibrocartilaginous joint between the left and right pubic bones

Sacroiliac – strong synovial joints between sacrum and ilium; holds weight of body Þ strongest ligaments in body

Sacrospinous Ligament – runs from lateral margin of coccyx and sacrum to the ischial tuberosity

Sacrotuberous Ligament – runs from the dorsal surface of the sacrum to the ischial tuberosity

Muscles

Gluteus Maximus

Origin: posterior gluteal line, tendon of sacrospinalis, dorsal surface of sacrum and coccyx, sacrotuberous ligament

Insertion: 1/3into the Gluteal tuberosity of femur, 2/3into the iliotibial tract

Function: extends thigh, assists in adducting and laterally rotating it; acting on insertion Þ extends trunk

Nerve: inferior gluteal

Artery: superior gluteal, inferior gluteal, 1^st perforating branch of profunda femoris

Obturator Internus

Origin: margins of the obturator foramen, obturator membrane, obturator fascia

Insertion: the medial surface of the greater trochanter

Function: rotates the thigh laterally, abducts the thigh when the limb is flexed

Nerve: nerve to the obturator internus and gemellus superior (L5 and S1)

Artery: muscular branches of the internal pudundal, superior gluteal

Piriformis

Origin: pelvic surface of sacrum between anterior sacral foramina, margin of greater sciatic foramen, sacrotuberus lig.

Insertion: the upper border of the greater trochanter of the femur

Function: rotates the thigh laterally, abducts the thigh when the limb is flexed

Nerve: ventral rami of S1 and S2

Artery: superior gluteal, inferior gluteal, internal pudundal

Sphincter Ani:

external anal sphincter – runs from the perineal body to the coccyx, surrounding the lower 2/3 of the anal canal

innervation: inferior rectal nerve

action: draws anal canal anteriorly, assisting in closing it (voluntary)

internal anal sphincter – thickened circular smooth muscle of the anus around the upper 2/3 of the anal canal

innervation: pelvic splanchnic nerve

action: closes the anal sphincter (involuntary)

Arteries (also see table below)

Inferior Rectal – branch of pudendal artery; supplies sphincter ani

Middle Rectal–branch of pudendal artery; runs medially to rectum; sends branches to prostate/seminal vesicles or vagina

Superior Gluteal – branch of the posterior division of the internal iliac; passes out of pelvis via greater sciatic foramen, superior to the piriformis muscle; supplies the gluteal muscles

Inferior Gluteal – branch of the anterior division of the internal iliac; passes out of pelvis via greater sciatic foramen, inferior to the piriformis muscle; supplies muscles and skin of the buttock and posterior surface of the thigh

Internal Pudendal–branch of internal iliac; passes out of pelvis via greater sciatic foramen, then enters ischioanal fossa via lesser sciatic foramen; continues along pudendal canal and splits into terminal branches (deep and dorsal arteries of the penis or clitoris) just before it reaches pubic symphysis. Other branches are inferior rectal artery perineal artery and (in the male) posterior scrotal artery

Nerves

Inferior Gluteal – from ventral rami of L5-S2; runs with inferior gluteal a; innervates gluteus maximus muscle

Sciatic–from ventral rami of L4-S3; largest nerve in body; passes through greater sciatic foramen; innervates lower limb

Pudendal–from ventral rami of S2-S4; follows the path of the internal pudendal a; innervates external anal sphincter via the inferior rectal nerve; terminates as the dorsal nerve of the penis or clitoris (provides sensory innervation)

Inferior Rectal – branch of the pudendal; innervates external anal sphincter

Other Structures and Terms

Pelvis – continuous with abdominal cavity; division of pelvis and abdomen is line from sacral prominatory to pubic symphysis

Perineum – diamond-shaped area extending from pubic symphysis to coccyx when legs are spread; inferior to the pelvic diaphragm

Pelvic Brim – line formed by the pubic crest, pectin pubis, arcuate line of the ilium and the sacral prominatory; separates the greater (false) from the lesser (true) pelvis

Greater and Lesser Pelvis – greater pelvis lies superior to the pelvic brim; lesser lies inferior

Pelvic Diaphragm – floor of the pelvis; formed by the two levator ani muscles and the coccygeus muscles

Anal Triangle – triangular half of the perineum posterior to a line connecting the ischial tuberosities; contains anal canal and ischioanal fossa

Urogenital Triangle – anterior half of the perineum; contains external genitalia

Urogenital Diaphragm – stretches between the two sides of the pubic arch; anterior and posterior fibers form the deep transverse perineal (transverse perineal profundus) muscles; middle fibers surround urethra (sphincter urethrae muscles)

Sphincter Urethrae – the middle fibers of the urogenital diaphragm; surround the membranous urethra

Transverse Perinel Profundus – the anterior and posterior fibers of the urogenital diaphragm

Ischiorectal Fossa – the space on either side of the rectum and anal canal; boundries: obturator internus/ischial tuberosity, pelvic diaphragm, gluteus maximus

Ischial Spine – superior posterior prominance of the ischium

Ischial Tuberosity – inferior posterior prominance of the ischium

Greater Sciatic Foramen – more superior; bounded by greater sciatic notch, sacrotuberus and sacrospinous ligaments

Lesser Sciatic Foramen – bounded by lesser sciatic notch, sacrotuberus and sacrospinous ligaments; more inferior

Obturator Foramen – formed by the ischium and the superior and inferior pubic rami

Structures: Urogenital Triangle, Pelvic Viscera, Pelvic Diaphragm

Ligaments

Suspensory ligament of the Penis – condensation of deep fascia; runs from pubic symphysis to fascia at base of penis

Suspensory Ligament of the Clitoris – analogous to suspensory ligament of penis

Puboprostatic Ligament – two bands of tissue derived from superior fascia of pelvic diaphragm; anchor neck of bladder to pubis

Broad Ligament of the Uterus – peritoneal fold that drapes over the uterus and attaches to the lateral walls and floor of the pelvic cavity; several other ligaments are a part of it:

Round Ligament of the Uterus – attaches to superior aspect of the uterus

Mesosalpinx – portion of the broad ligament that drapes over the uterine tubes

Mesovarium – portion that drapes over the ovaries

Suspensory Ligament of the Ovary – attaches ovary to lateral wall; contains ovarian vessels

Transverse Cervical Ligament – attaches cervix and lateral parts of vaginal fornix to the lateral pelvic walls

Fascia

Superficial Perineal (Colles'): fascial layer just deep to the dartos muscle; inner layer of the superficial perineal fascia

Dartos Fascia: muscle layer just deep to the skin of the scrotum; draws testes up into body

Muscles

Transverse Perinel Superficialis – at base of superficial perineal space; from the ischial ramus to the pubic body

Ischiocavernosus – medial to transverse perischial superficialis; pubic ramus to the crus of the clitorus or the penis (continuous with corpus cavernosus in penis)

Bulbospongiosus – most medial; perineal body to the clitoris or the penis (continuous with the corpus spongiosum)

Levator Ani (puborectalis, Ilio (pubo) coccygeus)–largest, most important muscles of pelvic floor; anterior to coccygeus muscle

Innervation: perineal branches of S3,S4

Action: support and are able to compress the pelvic viscera (vomiting, urinating, coughing, etc)

form a sling that attaches to the lateral walls of the pelvis, the coccyx, and the pubis Þ three parts:

(1) puborectalis – arises from the pubis, forms a sling around the anorectal junction; some fibers go around the vagina or prostate to insert in the perineal body
(2) pubococcygeus – main part of levator ani; runs from pubis to coccyx
(3) iliococcygeus – runs from obturator fascia and inserts on coccyx

Coccygeus – forms the minor part of the pelvic diaphragm; triangular in shape

lateral attachment – ischial spine and sacrotuberus ligament
medial attachment – lateral margin of coccyx and S5

Innervation: S4, S5

Action: assists levator ani

Arteries

Dorsal Arteries of the Penis – branches of the internal pudendal

Deep Dorsal Artery of the Penis – branches of the internal pudendal; primary blood supply used for erection

Internal lliac – branch of common iliac; gives rise to superior vesicular aa, internal pudendal, sup/inf gluteal

Obturator – branch of external iliac; passes through the obturator foramen; has muscular, pubic, ilial branches

Posterior Labial – branches of the internal pudendals

Veins

Deep Dorsal Vein of the Penis – drains the cavernous spaces of the penis into the prostatic plexus

Nerves

Perineal – from S3-S4; innervate levator ani and scrotum

Obturator – from L2-L4; passes through obturator foramen to innervate the adductors of the lower limb

Posterior Scrotal – branch of internal pudendal; supplies posterior aspect of scrotum and dartos muscle

Posterior Labial – analogous to posterior scrotal nerve

Sympathetic Trunk – tract of sympathetic nerves along either side of vertebral column, just medial to sacral foramina; contain four sympathetic ganglia; continuous with lumbar trunks; merge into the ganglion impar at their distal ends

Superior Hypogastric Plexus – sympathetic; continuation of intermesenteric plexus; gives rise to hypogastric nerves

Pelvic Splanchnic–parasympathetic nerves from S2-S4; merge with hypogastric nerves to form inferior hypogastric plexus

Sacral Plexus – arise form S1-S4; gives rise to sciatic and pudendal nerves

Other Structures and Terms

Retropubic Space – between the pubic bones and the bladder (male)

Rectovesical Fossa – posterior to the bladder and anterior to the rectum (male)

Paravesical Fossa – between the bladder and the anterior pelvic wall

Pararectal Fossa – between the rectum and the posterior pelvic wall

Vesicouterine Pouch – between the bladder and the uterus

Rectouterine Pouch – between the rectum and the uterus

Retrorectal Space – behind the rectum

Deep Perineal Space – enclosed by superficial and deep facial layers of the urogenital diaphragm

contents: urogenital diaphragm and deep dorsal vein of penis

Superficial Perineal Space – between superficial perineal fascia and perineal membrane of the urogenital diaphragm

contents in male: contents of scrotum, root of penis and associated muscles, pudendal nerves

contents in female: root of clitoris, bulbs of vestibule, superficial perineal muscles, greater vestibular glands

Conjugate Diameter – distance between the sacral promontory and the pubic symphysis (usually 11 cm)

Perineal Body – fibrous mass of tissue at the center of the perineum; convergence of muscles (transverse perineal, bulbospongiosis, levator ani, some fibers of external anal sphincter)

Spongy Urethra – longest portion of the male urethra; runs the length of the penis

Urinary Bladder–in abdomen as infant, continues to descend until in the pelvis minor at puberty; muscular and distensible

Trigone: triangular area in the base (fundus) of the bladder

Penis – male copulatory organ

Scrotum – cutaneous fibromuscular sac; contains testes and part of spermatic cord

Vagina – inferior portion of female genital tract; musculomembranous tube ~ 7-9 cm long

Cervix – cylindrical inferior 1/3 of the uterus

Uterus – three parts; body (superior 2/3); cervix; isthmus (narrowing at the junction of the body and cervix)

Ovary – glands situated in the ovarian fossa; 3cm long, 1.5 cm wide; 1cm thick

Uterine Tube (Fallopian tube) – 10-12 cm long, 1 cm diameter

Clitoris – 2-3 cm long, erectile organ; contains a root and a body, two corpora cavernosa and one corpus spongiosum; embryologically analagous to the glans penis

Vulva – collective name for the female external genital organs

Labia Majorum – fat-filled folds of skin which protect the vaginal vestibule; embryologically analagous to scrotum

Labia Minorum – thin, hairless tissue folds between the labia majora; many sensory nerves

Greater Vestibular Gland – located on either side of the vaginal vestibule; secrete lubricating mucous on sexual arousal

Bulb of the Vestibule – large, elongated masses of erectile tissue along the sides of the vaginal orifice

Prepuce – foreskin of the penis

Corpus Cavernosum – two cords of erectile tissue that lie on the dorsum of the penis

Corpus Spongiosum – cord of erectile tissue on ventral side of penis; contains the spongy urethra

Bulbourethral Glands – lie in deep perineal pouch, posterolateral to the membranous urethra

Prostate Gland – largest accessory organ of reproduction in males; walnut sized; prostatic urethra runs through it; contributes to 20% of seminal fluid

Peritoneum – lines viscera

Ureter – muscular ducts which drain kidneys into the bladder via peristalsis; retroperitoneal

Ejaculatory Duct – thin-walled tubes formed by merging of ductus deferens and ducts of seminal vesicles; open into prostatic urethra

Ductus Deferens – thick, muscular tube originates at epididymis, travels up the spermatic cord, along the anterior pelvic wall and merges with the ducts of the seminal vesicles to form the ejaculatory duct

Seminal Vesicle – thin-walled; pear-shaped; lie superior to the prostate

Arteries of the Pelvis

Arteries:	ORIGIN	COURSE	DISTRIBUTION
Common iliac	Abdominal aorta	Passes over inferior vena cava descending midline	External and internal iliac
External iliac	Common iliac	Splits off common anteriorly under the inguinal ligament becoming the femoral	Branches supply the anterior abdominal wall
Internal iliac	Common iliac	Passes over brim of pevis to reach pelvic cavity	Main blood supply to pelvic organs, gluteal rim, and perineum
Iliolumbar	Posterior division of internal iliac	Passes posteriorly and gives rise to parietal brances	Pelvic wall and gluteal region
Lateral sacral (superior and inferior)	Posterior division of internal iliac	Run on superficial aspect of piriformis	Piriformis and vertebral canal
Superior Gluteal	Posterior division of internal iliac	Leaves pelvis over the priforormis muscle	Priformis, gluteal muscles
Inferior gluteal	Anterior division of internal iliac	Leaves pelvis through greater sciatic foramen superior to the piriformis	Priformis, coccygeus, levator ani, and gluteal mm.
Obturator	Anterior division of internal iliac	Runs anterioinferiorly on lateral pelvic wall	Pelvic mm., nutrient artery to ilium and had of femur
Inferior vesical	Branch of middle rectal artery	Passes to inferior aspect of urinary bladder	Inferior aspect of urinary bladder
Superior vesical	Remnant of proximal part of umbilical artery	Passes to superior aspect of urinary bladder	Superior aspect of unrinary bladder
Uterine	Anterior division of internal iliac	Runs medially on levator ani crosses ureter to reach base of broad ligament	Uterus, ligament o futerus, uterine tube, and vagina
Ovarian	Branch of the uterine artery	Runs along the perineum of the fallopian tube supplying the ovary	Supplies the ovary
Vaginal	Anterior division of internal iliac	Runs laterally on levator ani crosses ureter to reach the vagina	Supplies the vagina