Review of Pevic Anatomyfor GynaecologistsProfessor Emeritus Moira OBrienFRCPI, FFSEM, FFSEM (UK), FTCDTrinity College Dublin

Female PelvisSmout et al., 1969

Overview

Pubic SymphysisSecondary cartilagenous jointArticular surface of medial aspect of body of pubisCovered with hyaline articular cartilageDisc of fibro-cartilage in between A cavity may develop in the disc but it is not lined with synovial membraneThere is normally very little movement at the pubic symphysis, except during the latter months of pregnancy

Sacroiliac JointModified synovial plane joint Articular surfaces are rough The capsule is attached just beyond the articular marginThe interosseous sacroiliac ligament is one of the strongest ligaments in the body and is posterior to the jointThis articulation is almost immobile, except during pregnancy

Sacrotuberous ligamentsSacrospinous ligamentsIliolumbar ligamentsPosterior superior iliac spine is middle of the joint posteriorly at the level S2S2 is end of dura, arachnoid mater and subarachnoid spaceDuring gait, the amount of accessory movement at the sacroiliac joint helps to protect the lumbar intervertebral discs Sacroiliac Joint Accessory Ligaments

Abnormalities of PelvisSpina bifida occultaUnilateral lumbarisationUnilateral sacralisationStress fractures of the sacrum, pubic arch and neck of femur may be first signs of osteoporosis

Walls of Pelvis Sacrum and coccyx posteriorOs coxae below pelvic brimPiriformis covers middle three pieces of sacrumPasses out of the pelvis through the greater sciatic foramenMusclesObturator internus muscleOrigin of levator aniCoccygeusSmout et al., 1969

Obturator nerveObturator artery and veinParietal peritoneum supplied by the obturator nervePain may be referred to hip or knee jointsCommon iliac divides into external and internal iliacInternal divides into anterior and posterior division branchesSmout et al., 1969

Lateral Walls of Pelvis

Pelvic FasciaPelvic fascia can be divided into three:1. Pelvic wall Pelvic fascia is a strong membrane over the piriformis and obturator internusFuses with the periosteum at their margins2. Pelvic floor Fascia is covered with loose areolar tissueLoose areolar fat tissue lies in the extraperitoneal space between peritoneum and the viscera forming a dead space

Pelvic Fascia3. Pelvic viscera Fascia of pelvic viscera is loose or dense depending on dispensability of organSmout et al., 1969

Pelvic LigamentsCondensation around vessels form ligaments in the pelvisCardinal ligament condensation of fascia around uterine arteryLateral ligament of the rectum is a condensation of fascia around the middle rectal vessels and branches of the hypogastric plexusWaldyers fascia suspends the lower part of the ampulla of the rectum to the hollow of sacrumContains the superior rectal vessels and lymphaticsSmout et al., 1969

Pelvic FloorUrogenital diaphragmPerineal membrane and the superficial transverse perineiiThe pelvic floor is a dome-shaped striated muscular sheet The levator ani is made up mainly of the pubococcygeus, the puborectalis and the iliococcygeusIt encloses the bladder, uterus and rectumTogether with the anal sphincters, has an important role in regulating storage and evacuation of urine and stoolStoker, 2009

Deep Perineal Pouch: Urogenital DiaphragmSuperior is the areolar tissue on the under surface of the levator aniThe sphincter urethrae around urethra and transverse perineii in the deep pouchPerineal membrane fills in pubic arch below the musclesMuscles are supplied by perineal branch of pudendal nerveIn lateral portion of the deep pouch, run dorsal nerve of clitoris and internal pudendal artery and vena commitans

superficial pouchdeep pouchsphincter urethraeperineal membrane

Levator AniArises, anteriorly, from the posterior surface of the body of pubis lateral to the symphysisPosterior from the inner surface of the spine of the ischiumBetween these two points, from a tendinous arch called the white line (arcus tendineus) adherent to the obturator fasciaLast,1984

Unites with the opposite side to form most of the floor of the pelvic cavityThe fibres pass downward and backward to the middle line of the floor of the pelvisInserted from before backwards, into perineal bodySide of the rectum and anal canalAnococcygeal rapheThe side of the last two segments of the coccyxLast 1984Levator Ani

The anterior fibres, pubovaginalis, pass behind the vagina, unites with the opposite sideInserted into the perineal body, the central point of the perineumJoining the fibres of the sphincter ani externus and transversus perineiiLast 1984

Levator Ani

Levator AniThe puborectalis forms a U-shaped sling, holding the anorectal anteriorly, blending with the deep fibres of the external anal sphincterAnococcygeal raphe lies between the coccyx and the margin of the anusNerve supply, inferior rectal nerve and perineal branch fourth sacralLast 1984

In women, the levator muscles or their nerve supply, can be damaged in pregnancy orchildbirthThere is some evidence that these muscles may also be damaged during ahysterectomyPelvic surgery using the "perineal approach" (between the anus and coccyx) is an established cause of damage to the pelvic floor. This surgery includes coccygectomyLevator Ani

Empty Female BladderBladder has a apex, triangular superior surface, base and two inferolateral surfaces, neck inferiorlyPosterior or base is fixed, the two ureters enter obliquely at the junction of the superior surfaces and baseThe internal urethral orifice or neck is at the junction of the base and two inferolateral surfaces The interior of the bladder is lined with transitional epithelium which is thrown into folds in the empty bladder, except for the smooth triangular area of base called trigone

Pubo vesical ligaments connect the neck to the pubic boneBase is attached to the supravaginal portion of the cervix and anterior fornix of vaginaPeritoneum only covers superior surfaceBlood supply, superior and inferior vesical arteriesVenous plexus into internal iliac veinFemale Bladder

Control of MicturitionSmooth or detrusor muscle at the neck is the internal sphincter, supplied by the sympatheticParasympathetic contracts detrusor muscle and relaxes internal sphincterSphincter urethra or external sphincter is striated muscleSupplied by perineal branch of pudendal nerve S2,3,4,

Structure of Female UrethraUrethra 3-5 cm longEnters deep pouch where it is surrounded bySphincter urethra, also called external sphincter of bladderUrethra pierces perineal membrane No fascia between lower two thirds of urethra and vaginaOpens into vestibule, between clitoris and vagina

Muscular layer continuous with bladderSpongy erectile tissue Plexus of veinsMucous membrane transitionalDistal non keratinising stratified squamous Para urethral glands and ducts open into urethra, homologues of prostatic glandsSmout et al 1969

Urethra

Urethra is supported by the fascia of the pelvic floor including pubo- vesical and pubocervical ligamentsIf this support is insufficient, the urethra can move downwards In times of increased abdominal pressure resulting in stress urinary incontinence (SUI)The physical changes that can occur during pregnancy, delivery and menopause can predispose to SUINuggaard and Heit in Bayliss 2010Urethra

Normal uterus is antevertedi.e. anterior to vertical plane going through the vaginaPosterior fornix deeperAnteflexed Bent anteriorly junction of body and cervixPear-shaped muscular organ8 cm long; 5 cm width; 3 cm thickNon-pregnant statePelvic organ

Uterus

FundusBodyCervix opens into vault or fornices of vaginaFundus is the portion above entrance of uterine tubesCovered with peritoneumBodyTriangular cavity

Uterus

Isthmus is a circular borderline area between the body and cervixIsthmus is the supra vaginal portion of cervix, the lower uterine segmentIntravaginal is surrounded by gutter by fornices of vagina,Posterior is deeper covered with peritoneumInternal os is the opening from the cavity of bodySpindle shaped cavity cervixExternal os is the opening into vaginaCervix

Cervical canal is lined by columnar epitheliumExternal os Junction of columnar of the cervical canal Stratified epithelium of the intravaginal portionSite of cancer of cervix Cervical smearAt birth cervix is larger than the bodyFully developedCervix is one third of body

Cervix

Supports of UterusUpperRound ligamentBroad ligament antevertedTransverse ligamentPubocervical UterosacralLowerLevator ani, coccygeusPerineal body

Round LigamentRound ligament and ligament of ovaryDevelop from the gubernaculumSide of uterus, junction fundus and bodyInguinal canal to labium majusAnte version

Pubocervical LigamentAttachedAnteriorly to posterior aspect of body of body of pubisPasses to neck of bladderAnterior fornix of vaginaPubocervical ligaments help toMaintain normal angle of 45 between the vagina and horizontalDecrease may cause a cystocoele

Transverse LigamentTransverse or cardinal or Mackenrodts ligamentThickening of visceral layer of pelvic fascia around uterine arteryLateral to medial in base of broad ligament

Uterosacral LigamentUterosacral contains fibrous tissueNon-striated muscleAttached from the cervix to the middle of sacrumContains lymphatics draining cervix to sacral glandsUterosacral help to keep uterus antevertedIf uterus is anteverted it cannot prolapse

Blood SupplyUterine from internal iliacOvarian from aorta at L2Vaginal arteries from internal iliacAnterior and posterior arcuate run in middle layer

Serous layerMyometriumNo submucous layerEndometrium Compact at surface of uterine cavity and spongy layer are supplied by spiral arteries Basal layer is not shed during menstruation; supplied by radial branchesVeins below arteryPlexus in lower edge broad ligament into internal iliacBlood Supply

Embolization of FibroidsFibroids vary in size and position in uterine wallMay enlarge and compress ureters or other structures in pelvisA small catheter is inserted in the groin, into the femoral arterySmall particles are introduced through the catheter into the uterine arteryThey block the blood supply to the fibroidsThe fibroids thus starved of blood shrivel and die over the next few months

Lymphatics of Uterus and Vagina

Nerve Supply of UterusPain from cervix via parasympathetic S2,3Pain from body via sympathetic to T11 and T12

Broad LigamentFold of peritoneum from side of uterus to side wall of pelvisFramework of pelvic fasciaParametric fatAnterior surface looks inferiorlyFree upper borderBase lies on pelvic floor

Uterine tubesOvarian vesselsUterine vesselsEpoophoronParoophoronRound ligament of uterus and ligament of ovaryTransverse ligamentOvary attached to posterior layerUreter in base below uterine arteryContents of Broad Ligament

Uterine tube lies in medial four fifths of free border of broad ligamentLateral one fifthContains ovarian vesselsInfundibulo-pelvic or suspensory ligament of ovaryEpoophoronParallel tubules remains of mesonephric tubules Gartner's duct remains of mesonephric duct, may form cystsBroad Ligament

Broad Ligament

Uterine TubeIntramuralIsthmusAmpullaInfundibulum surrounded by fimbriaLined ciliated columnar epitheliumBeats towards uterusPeritoneum loosely attached to ampullaTightly to isthmus, if ectopic implanted here, ruptures earlierFimbria surrounding opening into peritoneal cavityOvarian fimbria is longest

OvaryAttached to posterior layer of broad ligament meso ovarianCovered with germinal epitheliumRelated to side wall of pelvis which is covered with peritoneumObturator internus muscleObturator nerve supplies the parietal peritoneumPosterior to ovary is the ureterLigament of ovary medially

Obturator nerve supplies the parietal peritoneumIrritation of the peritoneum of the side wall by bleeding at ovulation or by lesions involving the ovaryMay result in referred pain to medial side of the thigh or the knee Ovary

Blood supplyOne ovarian artery from lateral aspects of aorta L2Right vein drains into inferior vena cavaLeft drains into left renal veinLymphatics into para aortic glands L2 Ovary

VaginaFornices, gutters which surround the cervixNormal anteverted antiflexedAnterior fornix is shallow anterior wall is shorter than posteriorPosterior deeper, covered with peritoneum of the pouch of DouglasMost dependent part of peritoneal cavityWalls in contact except superiorOpens into vestibule of vagina

Uterine ArteryUterine artery lies superior to the ureter at lateral fornix of vaginaBase of broad ligament

Erectile tissueMuscular wallPelvic fasciaNonkeratinised stratified squamous epitheliumUrethra lower third anterior wallNo fascia between lower two thirds of urethra and vaginaUpper portion of the vagina is clasped by the pubo-vaginalis portion of the levator aniVagina

Deep pouch Sphincter urethrae, deep transverse perineii, pierces perineal membrane, opens into vestibule of vaginaHymen fold of mucous membrane at external openingLateral are the bulbs of vestibuleCovered by bulbospongiosus muscleGreater vestibular (Bartholin's) glands lie behind the bulbs of vestibule Ducts open into orifice of the vagina Posterior to vagina is the perineal body

deep pouchsuperficialVagina

Perineumperineal body central point of perineum

Peritoneum on Uterus and VaginaReflected from the superior surface of the bladderJunction of the supravaginal portion of the cervix and the body of the uterus forming the utero vesical pouchPeritoneum then covers body, fundus and posterior surface body and then the supravaginal cervix and posterior fornix of vaginaPeritoneum then reflected on to junction of upper two thirds and lower third of rectum formingPouch of Douglas is most dependent part of female peritoneal cavity

Blood and Nerve Supply VaginaUterine arteryVaginalInternal pudendalLabialIlio Inguinal nerve supplies the anterior wallLabial nerves supply the posterior wall

Lymphatics of VaginaInternal iliacLower thirdMedial group of proximal superficial inguinal glands

Pelvic PlexusLumbar splanchnics L1-L2Presacral nerveAnterior to body of L5 Divide into pelvic plexusesPostganglionic of sympathetic that relayed in lumbar and sacral ganglia causes contraction of sphincters of bladder and anal canal

Pelvic ParasympatheticPreganglionic have cell bodies in lateral column of segments S2,3,4 Ganglia found close to or in wall of organSupplies intestine from splenic flexure to upper two thirds of anal canal, bladderMotor to walls and inhibitory to sphinctersParasympathetic causes erection

RectumRectum is a continuation of pelvic colon Starts at the third piece of the sacrum Ends 5 cm from the tip of coccyxLower end is dilated at the ampulla, at the anorectal junctionThere are no taeniae and no appendices epiplociae on the rectum

It has an antero-posterior curve, above it is angled anteriorly by the puborectalisBelow convex forwardsThree lateral curvesTwo concave to left, one to right, where the valves of Houston, which consist of circular muscle and mucous membrane Peritoneum covers upper third on front and sidesMiddle third on front, none on lower thirdRectum

Blood Supply of RectumSuperior rectal, continuation of inferior mesenteric arteryRuns in Waldyers fascia from hollow of sacrum to the lower part of the ampulla of the rectumSupplies mucous membrane as far mucocutaneous junction of anal canalVenous drainage into portal system Middle rectal the muscle layerSmall twigs from median sacral

Anal CanalStarts at anorectal junctionBelow ampulla of rectumPasses backwardsApprox 4 cmEnds at anus Anterior: perineal bodyPosterior: anococcygeal bodyLateral: ischiorectal fossae

Muscles of Anal CanalThe anal sphincter is a multilayered cylindrical structureThe inner smooth muscle of the internal sphincterSurrounds upper two thirdsLower two thirds the outer striated muscle layer of the external sphincterAnorectal ring formed by puborectalis and the deep part of the external sphincter

Peri Anal FasciaPerianal fascia continuation of longitudinal coat of rectum Medial to deep and superficial external sphinctersAttached at Hiltons linePasses to lateral wall Above subcutaneous sphincter

Lateral sheet passes between soft ischiorectal fat and subcutaneous fat to lateral wallSplits to form pudendal canal and isContinuous superiorly with the lunate fascia, which passes above soft ischiorectal fatIt is medial to deep and superficial sphincterAbove subcutaneous sphincter

Anal Canal

Puborectalis portion levator ani holds the anorectal junction anteriorlyDeep and subcutaneous parts of external are true sphinctersNo bony attachmentsSuperficial attached to coccyx and the perineal body

Muscles of Anal Canal

Anorectal ringInternal sphincterPuborectalisPuborectal fasciaExternal sphincterDeep, true sphincter, no bony attachmentsInferior rectal nerve S3,4Superficial S4Subcutaneous, true sphincterInferior rectal nerve S3,4

Muscles of Anal Canal

Upper two thirds lined bycolumnar epitheliumLower third by skinJunction of two is Hiltons white line skinAnal columns contain radicles of superior rectal artery and veins 4,7,11At the lower end joining the columns are mucosal folds called anal valvesAnal sinuses lie behindSkin supplied by inferior rectal vessels and nerves

Anal Canal

Blood and Nerve Supply Upper two thirdsColumnar epitheliumSuperior rectal arteryAutonomic nervesDerived from cloacaeLower thirdSkinInferior rectal S3,4,Somatic nervesDerived from proctodeum

Venous DrainageMucosa upper two thirdsSuperior rectal veinPortal systemLower thirdInferior rectal veinVein into systemic systemPortal systemic anastomosis 4,7,11

Lymphatic DrainageUpper thirdPre aortic inferior mesentericWaldeyers fascia passes from sacrum to the ampulla of rectumEncloses superior rectal vessels and lymphaticsInternal iliacLower ThirdInferior rectal cross ischio-rectal fossaMedial superficial inguinal glands

Anal SphinctersThe internal and external anal sphincters are primarily responsible for maintaining faecal continence at rest and when continence is threatened, respectively.Defecation is a somato-visceral reflex regulated by dual nerve supply (i.e. somatic and autonomic) to the anorectum.Bharucha 2006

Anal SphinctersThe net effects of sympathetic and cholinergic stimulation are to increase and reduce anal resting pressure, respectively.Faecal incontinence and functional defecatory disorders may result from structural changes and/or functional disturbances in the mechanisms of faecal continence and defecation.Bharucha 2006

Ischiorectal Fossa Ischiorectal fossa contentsSoft ischiorectal fatLunate fascia above the fatInferior rectal vessels pass above the fat to reach medial wallPerineal branch of S4

ischiorectal fossa

Ischiorectal fossa contentslunate fascia above the soft ischiorectal fatInferior rectal vessels and nerve pass above lunate fascia and the fat to reach medial wallSubcutaneous fat lies below perianal fasciaPerineal branch of S4 Lymphatics cross fossaIschiorectal Fossa

Pudendal CanalRuns posterior to anteriorPudendal canal contentsPudendal nerveInferior rectal nerveDorsal nerve of clitorisPerineal nerveLabial nervesInternal pudendal vessels

Pudendal BlockPudendal nerve Lies on the sacrospinous ligamentAnaesthetizes posterior wall of the vaginaIlioinguinal nerve supplies the anterior wall

Age, pregnancy, family history, and hormonal status all contribute to the development of pelvic organ prolapse. The vagina is suspended by attachments to the perineum, pelvic side wall and sacrum via attachments that include collagen, elastin, and smooth muscle. Surgery can be performed to repair pelvic floor muscles. The pelvic floor muscles can be strengthened withKegel exercises.

Disorders of the posterior pelvic floor includerectal prolapse,rectocele,perineal hernia, and a number of functional disorders includinganismus. Constipationdue to any of these disorders is called "functional constipation" and is identifiable by clinical diagnostic criteria.

BMJ Publishing Group Limited (BMJ Group) 2012. All rights reserved.

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