TRUE PELVIS AND PELVIC FLOOR

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Body_ID: HC108001

The true pelvis is a bowl-shaped structure formed from the sacrum, pubis, ilium, ischium, the ligaments which interconnect these bones and the muscles which line their inner surfaces. The true pelvis is considered to start at the level of the plane passing through the promontory of the sacrum, the arcuate line on the ilium, the iliopectineal line and the posterior surface of the pubic crest. This plane, or 'inlet' lies at an angle of between 35 and 50° up from the horizontal and above this the bony structures are sometimes referred to as the false pelvis. They form part of the walls of the lower abdomen. The floor or 'outlet' of the true pelvis is formed by the muscles of levator ani. Although the floor is gutter shaped, it generally lies in a plane between 5 and 15° up from the horizontal. This difference between the planes of the inlet and outlet is the reason why the true pelvis is said to have an axis (lying perpendicular to the plane of both inlet and outlet) which progressively changes through the pelvis from above downwards. The details of the topography of the bony and ligamentous pelvis is considered fully on page 1428

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Muscles and fasciae of the pelvis

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PELVIC MUSCLES (Figs 108.1, 108.2)

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Figure 108.1 Muscles of the male pelvis - lateral view. The superior gluteal and obturator vessels and nerves have been divided close to their exit from the pelvis. The rectum, bladder and upper prostate have been omitted for clarity.


The muscles arising within the pelvis form two groups. Piriformis and obturator internus, although forming part of the walls of the pelvis, are considered as primarily muscles of the lower limb. Levator ani and coccygeus form the pelvic diaphragm and delineate the lower limit of the true pelvis. The fasciae investing the muscles are continuous with visceral pelvic fascia above, perineal fascia below and obturator fascia laterally.

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PIRIFORMIS (See also p. 1357.)

Body_ID: HC108004

Piriformis forms part of the posterolateral wall of the true pelvis. It is attached to the anterior surface of the sacrum, the gluteal surface of the ilium near the posterior inferior iliac spine, the capsule of the adjacent sacroiliac joint and sometimes to the upper part of the pelvic surface of the sacrotuberous ligament. It passes out of the pelvis through the greater sciatic foramen. Within the pelvis, the anterior surface of piriformis is related to the rectum (especially on the left), the sacral plexus of nerves and branches of the internal iliac vessels. The posterior surface lies against the sacrum.

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(See also p. 1357.)

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Figure 108.2 Muscles of the female pelvis viewed from above. The sacral nerve roots have been divided close to the sacral foramina. The anorectal junction, vagina and urethra have been divided at the level of the pelvic floor.


Obturator internus and the fascia over its upper inner (pelvic) surface form part of the anterolateral wall of the true pelvis. It is attached to the structures surrounding the obturator foramen; the inferior ramus of the pubis, the ischial ramus, the pelvic surface of the hip bone below and behind the pelvic brim, and the upper part of the greater sciatic foramen. It also attaches to the medial part of the pelvic surface of the obturator membrane. The muscle is covered by a thick fascial layer and the fibres themselves cannot be seen directly from within the pelvis. This fascia gives attachment to some of the fibres of levator ani and thus only the upper portion of the muscle lies lateral to the contents of the true pelvis, whilst the lower portion forms part of the boundaries of the ischioanal fossa. In the male, the upper portion lies lateral to the bladder, the obturator and vesical vessels, and the obturator nerve. In the female, the attachments of the broad ligament of the uterus, the fallopian end of the uterine tubes, and the uterine vessels, also lie medial to obturator internus and its fascia.

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LEVATOR ANI (ISCHIOCOCCYGEUS, ILIOCOCCYGEUS, PUBOCOCCYGEUS)

Body_ID: HC108006

Levator ani is a broad muscular sheet of variable thickness attached to the internal surface of the true pelvis and forms a large portion of the pelvic floor. The muscle is subdivided into named portions according to their attachments and the pelvic viscera to which they are related. These parts are often referred to as separate muscles, but the boundaries between each part cannot be easily distinguished and they perform many similar physiological functions. The separate parts are referred to as ischiococcygeus, iliococcygeus and pubococcygeus. Pubococcygeus is often subdivided into separate parts according to the pelvic viscera to which they relate, i.e. pubourethralis and puborectalis in the male, pubovaginalis and puborectalis in the female. Levator ani arises from each side of the walls of the pelvis. Fibres from ischiococcygeus attach to the sacrum and coccyx but the remaining parts of the muscle converge in the midline. The fibres of iliococcygeus join by a partly fibrous intersection and form a raphe posterior to the anorectal junction. Closer to the anorectal junction and elsewhere in the pelvic floor, the fibres are more nearly continuous with those of the opposite side and the muscle forms a sling (puborectalis and pubovaginalis or pubourethralis).

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Attachments

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Ischiococcygeus

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The ischiococcygeal part may be referred to as a separate muscle, sometimes named coccygeus. It lies as the most posterosuperior portion of levator ani and arises as a triangular musculotendinous sheet with its apex attached to the pelvic surface and tip of the ischial spine. The base of the muscle is attached to the lateral margins of the coccyx and the fifth sacral segment. Ischiococcygeus is rarely absent, but may be nearly completely tendinous rather than muscular. It lies on the pelvic aspect of the sacrospinous ligament and may be fused with it, particularly if mostly tendinous. The sacrospinous ligament may represent a degenerate part or an aponeurosis of the muscle since the muscle and ligament are coextensive.

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Iliococcygeus

HC108010

The iliococcygeal part is attached to the inner surface of the ischial spine below and anterior to the attachment of ischiococcygeus and to the obturator fascia as far forward as the obturator canal (Fig. 108.1). The most posterior fibres are attached to the tip of the sacrum and coccyx but most join with fibres from the opposite side to form a raphe. This raphe is effectively continuous with the fibroelastic anococcygeal ligament, which is closely applied to its inferior surface and some muscle fibres may attach into the ligament. The raphe provides a strong attachment for the pelvic floor posteriorly and must be divided to allow wide excisions of the anorectal canal during abdominoperineal excisions for malignancy. An accessory slip may arise from the most posterior part and is sometimes referred to as iliosacralis.

P108009

Pubococcygeus

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Figure 108.3 Fasciae of the pelvis and perineum. Median sagittal section in the male. The deep fascia of the abdominal wall, the layers of the urogenital fascia and the mesorectal fascia are in green, the peritoneum in blue, the superficial fascia of the abdominal wall and perineum in red. Muscles are shown in brown.


The pubococcygeal part is attached to the back of the body of the pubis and passes back almost horizontally. The most medial fibres run directly lateral to the urethra and its sphincter as it passes through the pelvic floor. In males these fibres therefore lie lateral and inferior to the prostate and are referred to as pubourethralis. They form part of the urethral sphincter complex together with the intrinsic striated and smooth musculature of the urethra and fibres decussate across the midline directly behind the urethra. In females the fibres of this part of the muscle run further back to from a sling around the posterior wall of the vagina and are referred to as pubovaginalis. In both sexes fibres from this part of pubococcygeus attach to the perineal body and a few elements also attach to the anorectal junction. Some of these fibres, sometimes called puboanalis, decussate and blend with the longitudinal rectal muscle and fascial elements to contribute to the conjoint longitudinal coat of the anal canal. Behind the rectum some fibres of pubococcygeus form a tendinous intersection as part of the levator raphe but a thick muscular sling, puborectalis, wraps around the anorectal junction. Some fibres blend with those of the external anal sphincter.

Body_ID: P108010

Body_ID: HC108012

The superior, pelvic surface of levator ani is separated only by fascia (superior pelvic diaphragmatic, visceral and extraperitoneal (p. 1359) from the urinary bladder, prostate or uterus and vagina, rectum and peritoneum. Its inferior, perineal, surface forms the medial wall of the ischioanal fossa and the superior wall of the anterior recess of the fossa, both being covered by inferior pelvic diaphragmatic fascia. The posterior border is separated from the coccyx by areolar tissue. The medial borders of the two levator muscles are separated by the visceral outlet, through which pass the urethra, vagina, and anorectum.

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Vascular supply

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Levator ani is supplied by branches of the inferior gluteal artery, the inferior vesical artery and the pudendal artery.

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Innervation

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Fibres originating mainly in the second, third and fourth sacral spinal segments reach levator ani from below and above by a variety of routes (Wendell-Smith & Wilson 1991

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Actions

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Pubococcygeus is a lateral compressor of the various visceral canals which cross the pelvic floor. The puborectalis part also reinforces the external anal sphincter and helps to create the anorectal angle. It also reduces the anteroposterior dimension of the ano-urogenital hiatus. Iliococcygeus and, to a lesser extent, the less muscular ischiococcygeus, assist puborectalis in contributing to anorectal and urinary continence. It is well recognized that levator ani must relax appropriately to permit expulsion of urine and particularly faeces. Levator ani also forms much of the basin-shaped muscular pelvic diaphragm, which supports the pelvic viscera and it contracts with abdominal muscles and the abdominothoracic diaphragm to raise intra-abdominal pressure. Like the abdominothoracic diaphragm, but unlike abdominal muscles, levator ani is also active in the inspiratory phase of quiet respiration. In the pregnant female, the shape of the pelvic floor may help to direct the fetal head into the anteroposterior diameter of the pelvic outlet.

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PELVIC FASCIAE (Fig. 108.3)

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The pelvic fasciae may be conveniently divided into the parietal pelvic fascia, which mainly forms the coverings of the pelvic muscles, and the visceral pelvic fascia, which forms the coverings of the pelvic viscera, their supplying vessels and nerves. The visceral pelvic fascia is described with the pelvic viscera.

Body_ID: P108016

PARIETAL PELVIC FASCIA

Body_ID: HC108017

The parietal pelvic fascia on the pelvic surface of obturator internus is well differentiated as the obturator fascia. Above, it is connected to the posterior part of the arcuate line of the ilium, and is continuous with iliac fascia. Anterior to this, as it follows the line of origin of obturator internus, it is gradually separated from the attachment of the iliac fascia and a portion of the periosteum of the ilium and pubis spans between them. It arches below the obturator vessels and nerve, investing the obturator canal, and is attached anteriorly to the back of the pubis. Behind the obturator canal the fascia is markedly aponeurotic and gives a firm attachment to levator ani. Below the attachment of levator ani it is thin and forms part of the lateral wall of the ischioanal fossa in the perineum. It is continuous with the pelvic periosteum and thus the fascia over piriformis.

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FASCIA OVER PIRIFORMIS

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FASCIA OF THE PELVIC DIAPHRAGM

Body_ID: HC108019

The fascia of the pelvic diaphragm covers both of the surfaces of the pelvic diaphragm. On the lower surface is the thin inferior fascia of the pelvic diaphragm, which is continuous with the obturator fascia laterally. It covers the medial wall of the ischioanal fossa and blends below with fasciae on the urethral sphincter and the external anal sphincter. On the upper surface is the superior fascia of the pelvic diaphragm which is generally known clinically as the endopelvic fascia.

Body_ID: P108019

It is attached anteriorly to the back of the body of the pubis, c.2 cm above its lower border, and extends laterally across the superior ramus of the pubis, blending with the obturator fascia and continuing along an irregular line to the spine of the ischium. It is continuous posteriorly with the fascia over piriformis and the anterior sacrococcygeal ligament. Medially, the superior fascia of the pelvic diaphragm blends with the visceral pelvic fascia. The fascia over obturator internus above the attachment of levator ani is therefore composed of the obturator fascia itself, the superior and inferior pelvic diaphragmatic fasciae and fibres from levator ani. The thickening where these structures fuse is the tendinous arch of levator ani. Below it, within the superior fascia, is the tendinous arch of the pelvic fascia, a thick white band extending from the lower part of the symphysis pubis to the inferior margin of the spine of the ischium (arcus tendineous fasciae pelvis). This is the attachment of the lateral, 'true' ligament of the urinary bladder. Anteriorly the same fascia forms two thick bands, the paired puboprostatic ligaments in the male, or the pubourethral ligaments in the female.

Body_ID: P108020

PRESACRAL FASCIA

Body_ID: HC108020

The presacral fascia lies between the posterior aspect of the mesorectal fascia and the superior pelvic diaphragmatic fascia. It is a hammock-like sheet extending between the tendinous arches of the pelvic fascia on either side. Below, it extends to the anorectal junction, where it fuses with the posterior aspect of the mesorectal fascia at the level of the anorectal junction. Above, it can be traced to the origin of the superior hypogastric plexus where it becomes progressively thinner over the promontory of the sacrum and becomes continuous with the retroperitoneal tissues. The right and left hypogastric nerves and inferior hypogastric plexuses lie on its surface and the presacral veins lie immediately posterior to it. It forms a distinct layer which can be seen both on magnetic resonance images of the pelvis and during surgery. The fascia provides an important landmark because extension of rectal tumours through it signifiantly reduces the chance of curative resectional surgery being possible. Dissection in the plane posterior to it may result in bleeding from the presacral veins and, since the adventitia of the veins is partly attached to the posterior surface of the fascia, the haemorrhage may be severe because the veins are unable to contract down properly.

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UPDATE

Date Added: 30 August 2005

 

Abstract: Clinical anatomy of the pelvic floor.

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Click on the following link to view the abstract: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15152384&query_hl=10 Clinical anatomy of the pelvic floor. Fritsch H, Lienemann A, Brenner E et al: Adv Anat Embryol Cell Biol. 175:III-IX, 1-64, 2004.

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Vascular supply and lymphatic drainage of the pelvis

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The true pelvis contains the internal iliac arteries and veins as well as the lymphatics draining the majority of the pelvic viscera. The common and external iliac vessels as well as the lymphatics draining the lower limb lie along the pelvic brim and in the lower retroperitoneum, but are conveniently discussed together with the vessels of the true pelvis.

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ARTERIES OF THE PELVIS

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COMMON ILIAC ARTERIES

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P108023

Right common iliac artery

Body_ID: HC108026

The right common iliac artery is approximately 5 cm long and passes obliquely across part of the fourth and the fifth lumbar vertebral bodies. The sympathetic rami to the pelvic plexus and, at its division, the ureter, cross anterior to it. It is covered by the parietal peritoneum, which separates it from the coils of the small intestine. Posteriorly, it is separated from the fourth and fifth lumbar vertebral bodies and their intervening disc by the right sympathetic trunk, the terminal parts of the common iliac veins and the start of the inferior vena cava, the obturator nerve, lumbosacral trunk and iliolumbar artery. Lateral to its upper part are the inferior vena cava and the right common iliac vein and lower down is the right psoas major. The left common iliac vein is medial to the upper part.

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Left common iliac artery

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The left common iliac artery is shorter than the right and is approximately 4 cm long. Lying anterior to it are the sympathetic rami to the pelvic plexus, the superior rectal artery and, at its terminal bifurcation, the ureter. The sympathetic trunk, the fourth and fifth lumbar vertebral bodies and intervening disc, the obturator nerve, lumbosacral trunk and iliolumbar artery are all posterior to it. The left common iliac vein is posteromedial to the artery while the left psoas major lies lateral to it.

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Branches

Body_ID: HC108028

In addition to the external iliac and internal iliac terminal branches, each common iliac artery gives small branches to the peritoneum, psoas major, ureter, adjacent nerves and surrounding areolar tissue. Occasionally the common iliac artery gives rise to the iliolumbar artery and accessory renal arteries if the kidney is low lying.

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INTERNAL ILIAC ARTERIES (Fig. 108.4)

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Figure 108.4 Arteries of the male pelvis. The internal iliac vein and its tributaries and the rectum have been omitted for clarity.


Each internal iliac artery, c.4 cm long, begins at the common iliac bifurcation, level with the lumbosacral intervertebral disc and anterior to the sacroiliac joint. It descends posteriorly to the superior margin of the greater sciatic foramen where it divides into an anterior trunk, which continues in the same line towards the ischial spine, and a posterior trunk, which passes back to the greater sciatic foramen. Anterior to the artery are the ureter and, in females, the ovary and fimbriated end of the uterine tube. The internal iliac vein, lumbosacral trunk and sacroiliac joint are posterior. Lateral is the external iliac vein, between the artery and psoas major and inferior to this is the obturator nerve. The parietal peritoneum is medial, separating it from the terminal ileum on the right and the sigmoid colon on the left. Tributaries of the internal iliac vein are also medial.

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In the fetus the internal iliac artery is twice the size of the external and is the direct continuation of the common iliac artery. The main trunk ascends on the anterior abdominal wall to the umbilicus, converging on the contralateral artery. The two arteries run through the umbilicus to enter the umbilical cord as the umbilical arteries. At birth, when placental circulation ceases, only the pelvic segment remains patent as the internal iliac artery and part of the superior vesical artery; the remainder becomes a fibrous medial umbilical ligament. In males, the patent part usually gives off an artery to the vas deferens.

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Posterior trunk branches

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Iliolumbar artery

Body_ID: HC108032

The iliolumbar artery is the first branch of the posterior trunk and ascends laterally anterior to the sacroiliac joint and lumbosacral nerve trunk. It lies posterior to the obturator nerve and external iliac vessels and reaches the medial border of psoas major, dividing behind it into the lumbar and iliac branches. The lumbar branch supplies psoas major and quadratus lumborum and anastomoses with the fourth lumbar artery. It sends a small spinal branch through the intervertebral foramen between the fifth lumbar and first sacral vertebrae, to supply the cauda equina. The iliac branch supplies iliacus; between the muscle and bone it anastomoses with the iliac branches of the obturator artery. A large nutrient branch enters an oblique canal in the ilium. Other branches runs around the iliac crest, contribute to the supply of the gluteal and abdominal muscles, and anastomose with the superior gluteal, circumflex iliac and lateral circumflex femoral arteries.

Body_ID: P108030

Lateral sacral arteries

Body_ID: HC108033

The lateral sacral arteries are usually double or if single divide rapidly into superior and inferior branches. The superior and larger artery passes medially into the first or second anterior sacral foramen, supplies the sacral vertebrae and contents of the sacral canal and leaves the sacrum via the corresponding dorsal foramen to supply the skin and muscles dorsal to the sacrum. The inferior or lateral sacral artery crosses obliquely anterior to piriformis and the sacral anterior spinal rami, then descends lateral to the sympathetic trunk to anastomose with its fellow and the median sacral artery anterior to the coccyx. Its branches enter the anterior sacral foramina and are distributed like those of the superior artery.

Body_ID: P108031

Superior gluteal artery

Body_ID: HC108034

The superior gluteal artery is the largest branch of the internal iliac and effectively forms the main continuation of its posterior trunk. It runs posteriorly between the lumbosacral trunk and the first sacral ramus or between the first and second rami, then turns slightly inferiorly leaving the pelvis by the greater sciatic foramen above piriformis and dividing into superficial and deep branches. In the pelvis it supplies piriformis, obturator internus and a nutrient artery to the ilium. The superficial branch enters the deep surface of gluteus maximus. Its numerous branches supply the muscle and anastomose with the inferior gluteal branches while others perforate the tendinous medial attachment of the muscle to supply the skin over the sacrum where they anastomose with the posterior branches of the lateral sacral arteries. The deep branch of the superior gluteal artery passes between gluteus medius and the bone, soon dividing into superior and inferior branches. The superior branch skirts the superior border of gluteus minimus to the anterior superior iliac spine and anastomoses with the deep circumflex iliac artery and the ascending branch of the lateral circumflex femoral artery. The inferior branch runs through gluteus minimus obliquely, supplies it and gluteus medius and anastomoses with the lateral circumflex femoral artery. A branch enters the trochanteric fossa to join the inferior gluteal artery and ascending branch of the medial circumflex femoral artery while other branches run through gluteus minimus to supply the hip joint.

Body_ID: P108032

The superior gluteal artery occasionally arises directly from the internal iliac artery with the inferior gluteal artery and sometimes from the internal pudendal artery.

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Anterior trunk branches

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Superior vesical artery (See also p. 1361.)

Body_ID: HC108037

The superior vesical artery is the first large branch of the anterior trunk. It lies on the lateral wall of the pelvis just below the brim and runs anteroinferiorly medial to the periosteum of the posterior surface of the pubis. It supplies the distal end of the ureter, the bladder, the proximal end of the vas deferens and the seminal vesicles. It also gives origin to the umbilical artery in the foetus, which remains as a fibrous cord, the medial umbilical ligament, in the adult. This vessel occasionally remains patent as a small artery supplying the umbilicus.

Body_ID: P108034

Inferior vesical artery (See also p. 1361.)

Body_ID: HC108038

The inferior vesical artery may arise as a common branch with the middle rectal artery. In the female it is often replaced by the vaginal artery. It supplies the bladder, the prostate, the seminal vesicles and the vas deferens.

Body_ID: P108035

Middle rectal artery (See also p. 1361.)

Body_ID: HC108039

The middle rectal artery is often multiple and may be small. It runs into the lateral fascial coverings of the mesorectum. It occasionally arises close to or in common with the origin of the inferior vesical artery in males.

Body_ID: P108036

Vaginal artery (See also p. 1361.)

Body_ID: HC108040

In females the vaginal artery may replace the inferior vesical artery. It may arise from the uterine artery close to its origin.

Body_ID: P108037

Obturator artery

Body_ID: HC108041

The obturator artery runs anteroinferiorly from the anterior trunk on the lateral pelvic wall to the upper part of the obturator foramen. It leaves the pelvis via the obturator canal and divides into anterior and posterior branches. In the pelvis it is related laterally to the fascia over obturator internus and is crossed on its medial aspect by the ureter and, in the male, by the vas deferens. In the nulliparous female the ovary lies medial to it. The obturator nerve is above the artery, the obturator vein below it. In the pelvis the obturator artery provides iliac branches to the iliac fossa. These supply the bone and iliacus and anastomose with the iliolumbar artery. A vesical branch runs medially to the bladder and sometimes replaces the inferior vesical branch of the internal iliac artery. A pubic branch usually arises just before the obturator artery leaves the pelvis, and ascends over the pubis to anastomose with the contralateral artery and the pubic branch of the inferior epigastric artery.

Body_ID: P108038

Outside the pelvis the anterior and posterior terminal branches encircle the foramen between obturator externus and the obturator membrane. The anterior branch curves anteriorly on the membrane and then inferiorly along its anterior margin to supply branches to obturator externus, pectineus, the femoral adductors and gracilis. It anastomoses with the posterior branch and the medial circumflex femoral artery. The posterior branch follows the posterior margin of the foramen and turns anteriorly on the ischial part to anastomose with the anterior branch. It supplies the muscles attached to the ischial tuberosity and anastomoses with the inferior gluteal artery. An acetabular branch enters the hip joint at the acetabular notch, ramifies in the fat of the acetabular fossa and sends a branch along the ligament of the femoral head.

Body_ID: P108039

Occasionally the obturator artery is replaced by an enlarged pubic branch of the inferior epigastric artery (p. 1101) which descends almost vertically to the obturator foramen. It usually lies near the external iliac vein, lateral to the femoral ring, and is rarely injured during inguinal or femoral hernia surgery. Sometimes it curves along the edge of the lacunar part of the inguinal ligament, partly encircling the neck of a hernial sac, and may be inadvertently cut during enlargement of the femoral ring in reducing a femoral hernia.

Body_ID: P108040

Uterine artery (See also p. 1361.)

Body_ID: HC108042

The uterine artery is an additional branch in females. It is a large branch which arises below the obturator artery on the lateral wall of the pelvis and runs inferomedially into the broad ligament of the uterus.

Body_ID: P108041

Internal pudendal artery (in the pelvis) (See also

Body_ID: HC108043

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Body_ID: P1362

Body_ID: P108042

Inferior gluteal artery

Body_ID: HC108044

The inferior gluteal artery is the larger terminal branch of the anterior internal iliac trunk and principally supplies the buttock and thigh. It descends posteriorly, anterior to the sacral plexus and piriformis but posterior to the internal pudendal artery. It passes between the first and second or second and third sacral anterior spinal nerve rami, then between piriformis and ischiococcygeus. It runs through the lower part of the greater sciatic foramen to reach the gluteal region. The artery runs inferiorly between the greater trochanter and ischial tuberosity with the sciatic and posterior femoral cutaneous nerves deep to gluteus maximus. It continues down the thigh, supplying the skin and anastomosing with branches of the perforating arteries. The inferior gluteal and internal pudendal arteries often arise as a common stem from the internal iliac, sometimes with the superior gluteal artery. Inside the pelvis the inferior gluteal artery gives branches to piriformis, ischiococcygeus and iliococcygeus. Occasionally it contributes to the middle rectal arterial supply and, in the male, supplies vessels to the seminal vesicles and prostate.

P108043

EXTERNAL ILIAC ARTERIES

Body_ID: HC108045

The external iliac arteries are of larger calibre than the internal iliac artery. Each artery descends laterally along the medial border of psoas major from the common iliac bifurcation to a point midway between the anterior superior iliac spine and the symphysis pubis. It enters the thigh posterior to the inguinal ligament to become the femoral artery.

Body_ID: P108044

On the right the artery is separated from the terminal ileum and, usually, the appendix by the parietal peritoneum and extraperitoneal tissue. On the left the artery is separated from the sigmoid colon and coils of the small intestine lie anteromedially. At its origin the artery may be crossed by the ureter. It is also crossed by the gonadal vessels, the genital branch of the genitofemoral nerve, the deep circumflex iliac vein and the vas deferens (male) or round ligament (female). Posterior to the artery the iliac fascia separates it from the medial border of psoas major. The external iliac vein lies partly posterior to its upper part but is more medial to it below. Laterally, it is related to psoas major which is covered by the iliac and psoas fascia. Numerous lymph vessels and nodes lie on its front and sides.

Body_ID: P108045

The external iliac artery is principally the artery of the lower limb and as such has few branches in the pelvis. Apart from very small vessels to psoas major and neighbouring lymph nodes, the artery has no branches until it gives off the inferior epigastric and deep circumflex iliac arteries which arise near to its passage under the inguinal ligament.

Body_ID: P108046

Deep circumflex iliac artery

HC108048

The deep circumflex iliac artery branches laterally from the external iliac artery almost opposite the origin of the inferior epigastric artery. It ascends and runs laterally to the anterior superior iliac spine behind the inguinal ligament in a sheath formed by the union of the transversalis and iliac fasciae. There it anastomoses with the ascending branch of the lateral circumflex femoral artery, pierces the transversalis fascia and skirts the internal lip of the iliac crest. About halfway along the iliac crest it runs through transversus abdominis and then between transversus and internal oblique to anastomose with the iliolumbar and superior gluteal arteries. At the anterior superior iliac spine it gives off a large ascending branch, which runs between internal oblique and transversus abdominis. It supplies both muscles and anastomoses with the lumbar and inferior epigastric arteries.

Body_ID: P108047

Inferior epigastric arteryp. 1362.)

Body_ID: HC108049

The inferior epigastric artery originates from the external iliac artery posterior to the inguinal ligament. It curves forwards in the anterior extraperitoneal tissue and ascends obliquely along the medial margin of the deep inguinal ring where it continues as an artery of the anterior abdominal wall.

Body_ID: P108048

VEINS OF THE PELVIS

Body_ID: HC108050

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COMMON ILIAC VEINS (Fig. 108.5)

HC108051

The common iliac vein is formed by the union of external and internal iliac veins, anterior to the sacroiliac joints. It ascends obliquely to end at the right side of the fifth lumbar vertebra, uniting at an acute angle with the contralateral vessel to form the inferior vena cava. The right common iliac vein is shorter and more nearly vertical, lying posterior then lateral to its artery. The right obturator nerve passes posterior. The left common iliac vein is longer and more oblique and lies first medial, then posterior to its artery. It is crossed anteriorly by the attachment of the sigmoid mesocolon and superior rectal vessels. Each vein receives iliolumbar and sometimes lateral sacral veins. The left common iliac usually drains the median sacral vein. There are no valves in these veins. The left common iliac vein occasionally ascends to the left of the aorta to the level of the kidney where it receives the left renal vein and crosses anterior to the aorta to join the inferior vena cava. This vessel represents the persistent caudal half of the left postcardinal or supracardinal vein.

Body_ID: P108050

Median sacral veins

Body_ID: HC108054

The medial sacral veins accompany the corresponding artery anterior to the sacrum, and unite to form a single vein which usually ends in the left common iliac vein. Sometimes it ends at the common iliac junction.

Body_ID: P108051

Internal pudendal veins

Body_ID: HC108055

The internal pudendal veins are venae comitantes of the internal pudendal artery. They unite as a single vessel ending in the internal iliac vein. They receive veins from the penile bulb and the scrotum (males) or clitoris and labia (females) and the inferior rectal veins.

Body_ID: P108052

Body_ID: P108053

F71683-108-f005

Body_ID: F108005

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Body_ID: P1363

 

 


INTERNAL ILIAC VEIN

Body_ID: HC108056

The internal iliac vein is formed by the convergence of several veins above the greater sciatic foramen. It does not have the predictable trunks and branches of the internal iliac artery but its branches drain the same territories. It ascends posteromedial to the internal iliac artery to join the external iliac vein, forming the common iliac vein at the pelvic brim, anterior to the lower part of the sacroiliac joint. It is covered anteromedially by parietal peritoneum. Its tributaries are the gluteal, internal pudendal and obturator veins, which originate outside the pelvis; the lateral sacral veins which run from the anterior surface of the sacrum; and the middle rectal, vesical, uterine and vaginal veins which originate in the venous plexuses of the pelvic viscera.

Body_ID: P108054

The venous drainage of the leg may be blocked by thrombosis involving the external iliac systems and the inferior vena cava. Under these circumstances, the pelvic veins, particularly the internal iliac tributaries, enlarge and provide a major avenue of venous return from the femoral system. Surgical interference with these veins may seriously compromise venous drainage and precipitate oedema of one or both legs.

Body_ID: P108055

Superior gluteal veins

Body_ID: HC108059

The superior gluteal veins are the venae comitantes of the superior gluteal artery. They receive branches corresponding to branches of the artery and enter the pelvis via the greater sciatic foramen, above piriormis. They join the internal iliac vein, frequently as a single trunk.

Body_ID: P108056

Inferior gluteal veins

Body_ID: HC108060

Doyle 1970) analogous to the sural perforating veins. They probably have a venous 'pumping' role, and provide collaterals between the femoral and internal iliac veins.

Body_ID: P108057

Obturator vein

HC108061

The obturator vein begins in the proximal adductor region and enters the pelvis via the obturator foramen. It runs posteriorly and superiorly on the lateral pelvic wall below the obturator artery and between the ureter and internal iliac artery to end in the internal iliac vein. It is sometimes replaced by an enlarged pubic vein, which joins the external iliac vein.

P108058

Lateral sacral veins

Body_ID: HC108062

The lateral sacral veins accompany the lateral sacral arteries, and are interconnected by a sacral venous plexus.

Body_ID: P108059

Middle rectal vein

Body_ID: HC108063

The middle rectal vein begins in the rectal venous plexus and drains the rectum and mesorectum. It often receives tributaries from the bladder and the prostate and seminal vesicle (males) and the posterior aspect of the vagina (females). It is variable in size and runs laterally on the pelvic surface of levator ani to end in the internal iliac vein.

Body_ID: P108060

EXTERNAL ILIAC VEIN

Body_ID: HC108064

The external iliac vein is the proximal continuation of the femoral vein. It begins posterior to the inguinal ligament, ascends along the pelvic brim and ends anterior to the sacroiliac joint by joining the internal iliac vein to form the common iliac vein. On the right it lies medial to the external iliac artery, gradually inclining behind it as it ascends. On the left it is wholly medial. Disease of the external iliac artery may cause it to adhere closely to the vein at the point where it is in contact, and, particularly on the right side, the walls of the vessels may become fused, making dissection hazardous. Medially the external iliac vein is crossed by the ureter and internal iliac artery. In males it is crossed by the vas deferens, in females by the round ligament and ovarian vessels. Lateral to it lies psoas major, except where the artery intervenes. The vein is usually valveless, but may contain a single valve. It tributaries are the inferior epigastric, deep circumflex iliac and pubic veins.

Body_ID: P108061

Inferior epigastric vein

Body_ID: HC108067

One or two inferior epigastric veins accompany the artery and drain into the external iliac vein a little above the inguinal ligament.

Body_ID: P108062

 

Body_ID: HC108068

The deep circumflex vein is formed from venae comitantes of the corresponding artery. It joins the external iliac vein a little above the inferior epigastric veins after crossing anterior to the external iliac artery.

Body_ID: P108063

Pubic vein

Body_ID: HC108069

The pubic vein connects the external iliac and the obturator vein. It ascends on the pelvic surface of the pubis with the pubic branch of the inferior epigastric artery. It sometimes replaces the normal obturator vein.

Body_ID: P108064

LYMPHATIC DRAINAGE OF THE PELVIS

Body_ID: HC108070

COMMON ILIAC NODES (Fig. 108.6)

Body_ID: HC108071

The common iliac nodes are grouped around the artery, and one or two lie inferior to the aortic bifurcation and anterior to the fifth lumbar vertebra or sacral promontory. They drain the external and internal iliac nodes and connect to the lateral aortic nodes. They usually lie in medial, lateral and anterior chains around the artery, the lateral being the main route. Since they receive drainage from both internal and external iliac nodes, the common iliac nodes receive the entire lymphatic drainage of the lower limb.

Body_ID: P108065

EXTERNAL ILIAC NODES

Body_ID: HC108072

The external iliac nodes usually form three subgroups, lateral, medial and anterior to the external iliac vessels. The medial nodes are considered the main channel of drainage, collecting lymph from the lower limb via the inguinal nodes, the deeper layers of the infra-umbilical abdominal wall, the adductor region of the thigh, the glans penis or clitoris, the membranous urethra, prostate, fundus of the bladder, uterine cervix and upper vagina. Their efferents pass to the common iliac nodes.

Body_ID: P108066

Inferior epigastric and circumflex iliac nodes

Body_ID: HC108075

The inferior epigastric and circumflex iliac nodes are associated with their vessels and drain the corresponding areas to the external iliac nodes.

Body_ID: P108067

INTERNAL ILIAC NODES (Fig. 108.7)

Body_ID: HC108076

Body_ID: P108069

F71683-108-f006

Body_ID: F108006

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Body_ID: P1364

 

Figure 108.6 Lymphatic drainage of the male pelvis and urinary bladder.


Body_ID: P108070

F71683-108-f007

Body_ID: F108007

 

Figure 108.7 Lymphatic drainage of the female pelvis. (After Cuneo and Marcille.)


The internal iliac nodes surround the branches of the internal iliac vessels and receive afferents from most of the pelvic viscera (with the exception of the gonads and the rectum), deeper parts of the perineum and the gluteal and posterior femoral muscles. They drain to the common iliac nodes. The individual groups are considered in the description of the viscera. There are frequent connections between the right and left groups particularly when they lie close to the anterior and posterior midlines.

Body_ID: P108068

Innervation of the pelvis

HC108077

The pelvis contains the lumbosacral nerve trunk, the sacral plexus, the coccygeal plexus and the pelvic parts of the sympathetic and parasympathetic systems. These supply the somatic and autonomic innervation to the majority of the pelvic visceral organs, the pelvic floor and perineum, the gluteal region and the lower limb.

Body_ID: P108071

The ventral rami of the sacral and coccygeal spinal nerves form the sacral and coccygeal plexuses. The upper four sacral ventral rami enter the pelvis by the anterior sacral foramina, the fifth between the sacrum and coccyx, while that of the coccygeal nerve curves forwards below the rudimentary transverse process of the first coccygeal segment. The first and second sacral ventral rami are large, the third to fifth diminish progressively and the coccygeal is the smallest. Each receives a grey ramus communicans from a corresponding sympathetic ganglion. Visceral efferent rami leave the second to fourth sacral rami as pelvic splanchnic nerves, containing parasympathetic fibres which reach minute ganglia in the walls of the pelvic viscera.

Body_ID: P108072

LUMBOSACRAL TRUNK AND SACRAL PLEXUS (Fig. 111.41)

HC108078

The sacral plexus is formed by the lumbosacral trunk, the first to third sacral ventral rami and part of the fourth, the remainder of the last joining the coccygeal plexus.

Body_ID: P108073

The lumbar part of the lumbosacral trunk contains part of the fourth and all the fifth lumbar ventral rami; it appears at the medial margin of psoas major, and descends over the pelvic brim anterior to the sacroiliac joint to join the first sacral ramus. The greater part of the second and third sacral rami converge on the inferomedial aspect of the lumbosacral trunk in the greater sciatic foramen to form the sciatic nerve. The ventral and dorsal divisions of the nerves do not separate physically from each other but the fibres remain separate within the rami, and ventral and dorsal divisions of each contributing root join within the sciatic nerve. The fibres of the dorsal divisions will go on to form the common peroneal nerve and the ventral division fibres form the tibial nerve. The sciatic nerve occasionally divides into common peroneal and tibial nerves inside the pelvis. In these cases the common peroneal nerve usually runs through piriformis.

Body_ID: P108074

The sacral plexus lies against the posterior pelvic wall anterior to piriformis, posterior to the internal iliac vessels and ureter, and behind the sigmoid colon on the left. The superior gluteal vessels run between the lumbosacral trunk and first sacral ventral ramus or between the first and second sacral rami, while the inferior gluteal vessels lie between the first and second or second and third sacral rami (Fig. 108.8).

P108075

The sacral plexus is not commonly involved in malignant tumours of the pelvis because in lies behind the relatively dense presacral fascia which resists all but locally very advanced malignant infiltration. When it occurs, there is intractable pain in the distribution of the branches of the plexus which may be very difficult to treat. The plexus may also be involved in the reticuloses or be affected by plexiform neuromas.

Body_ID: P108076

UPDATE

 

Publication Services, Inc.

Abstract: Urinary and sexual function after total mesorectal excision. Recent results

Body_ID: PUP20060306E001

Click on the following line to view the abstract: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15865034&query_hl=6&itool=pubmed_docsum Urinary and sexual function after total mesorectal excision. Recent results. Maurer CA: Cancer Res 165:196-204, 2005.

Body_ID: None


BRANCHES OF THE SACRAL PLEXUS

Body_ID: HC108079

Body_ID: TI108001



Ventral divisions

Dorsal divisions

Body_ID: TI108001.50



Nerve to quadratus femoris and gemellus inferior

 

 

Body_ID: TI108001.100



Nerve to obturator internus and gemellus superior

L5, S1,2

 

Body_ID: TI108001.150



Nerve to piriformis

 

S2 (S1)

Body_ID: TI108001.200



Superior gluteal nerve

 

L4,5, S1

Body_ID:



Inferior gluteal nerve

 

L5, S1,2

Body_ID: TI108001.300



Posterior femoral cutaneous nerve

S2,3

S1,2

Body_ID: TI108001.350



Tibial (sciatic) nerve

L4,5, S1,2,3

 

Body_ID: TI108001.400



 

L4,5, S1,2

Body_ID: TI108001.450



Perforating cutaneous nerve

 

S2,3

Body_ID: TI108001.500



Pudendal nerve

S2,3,4

 

Body_ID: TI108001.550



Nerves to levator ani and external anal sphincter

S4

 

Body_ID: TI108001.600



Pelvic splanchnic nerves

 

S2,3 (S4)

Body_ID: TI108001.650



Body_ID: TI108001

Body_ID: None

 



The branches of the sacral plexus are: The course and distribution of most of the branches of the sacral plexus are covered fully on page 1456.

Body_ID: P108077

PUDENDAL NERVE (IN THE PELVIS)

Body_ID: HC108080

The pudendal nerve arises from the ventral divisions of the second, third and fourth sacral ventral rami and is formed just above the superior border of the sacrotuberous ligament and the upper fibres of ischiococcygeus. It leaves the pelvis via the greater sciatic foramen between piriformis and ischiococcygeus, enters the gluteal region and crosses the sacrospinous ligament close to its attachment to the ischial spine. The nerve lies medial to the internal pudendal vessels on the spine. It accompanies the internal pudendal artery through the lesser sciatic foramen into the pudendal (Alcock's) canal on the lateral wall of the ischioanal fossa. In the posterior part of the canal it gives rise to the inferior rectal nerve, the perineal nerve and the dorsal nerve of the penis or clitoris.

Body_ID: P108078

SACRAL VISCERAL BRANCHES

Body_ID: HC108081

These arise from the second to fourth sacral ventral rami to innervate the pelvic viscera; they are termed pelvic splanchnic nerves.

Body_ID: P108079

SACRAL MUSCULAR BRANCHES

Body_ID: HC108082

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Body_ID: P1365

Body_ID: P108081

F71683-108-f008

Body_ID: F108008

 

Figure 108.8 The lumbosacral plexus in the pelvis. The pelvic viscera have been omitted for clarity.


Several muscular branches arise from the fourth sacral ventral ramus to supply the superior surface of levator ani and the upper part of the external anal sphincter. The branches to levator ani enter the superior (pelvic) surface of the muscle whilst the branch to the external anal sphincter (also referred to as the perineal branch of the fourth sacral nerve) reaches the ischioanal fossa by running through ischiococcygeus or between ischiococcygeus and iliococcygeus. It supplies the skin between the anus and coccyx via its cutaneous branches.

Body_ID: P108080

COCCYGEAL PLEXUS

Body_ID: HC108083

The coccygeal plexus is formed by a small descending branch from the fourth sacral ramus and by the fifth sacral and coccygeal ventral rami. The fifth sacral ventral ramus emerges from the sacral hiatus, curves round the lateral margin of the sacrum below its cornu and pierces ischiococcygeus from below to reach its upper, pelvic surface. Here it is joined by a descending branch of the fourth sacral ventral ramus, and the small trunk so formed descends on the pelvic surface of ischiococcygeus. They join the minute coccygeal ventral ramus which emerges from the sacral hiatus and curves round the lateral coccygeal margin to pierce coccygeus to reach the pelvis. This small trunk is the coccygeal plexus. Anococcygeal nerves arise from it and form a few fine filaments which pierce the sacrotuberous ligament to supply the adjacent skin.

Body_ID: P108082

PELVIC PART OF THE SYMPATHETIC SYSTEM

Body_ID: HC108084

The pelvic sympathetic trunk lies in the extraperitoneal tissue anterior to the sacrum beneath the presacral fascia. It lies medial or anterior to the anterior sacral foramina and has four or five interconnected ganglia. Above, it is continuous with the lumbar sympathetic trunk. Below the lowest ganglia the two trunks converge to unite in the small ganglion impar anterior to the coccyx. Grey rami communicantes pass from the ganglia to sacral and coccygeal spinal nerves but there are no white rami communicantes. Medial branches connect across the midline and twigs from the first two ganglia join the inferior hypogastric plexus or the hypogastric 'nerve'. Other branches form a plexus on the median sacral artery.

Body_ID: P108083

VASCULAR BRANCHES

Body_ID: HC108085

Postganglionic fibres pass through the grey rami communicantes to the roots of the sacral plexus. Those forming the tibial nerve are conveyed to the popliteal artery and its branches in the leg and foot whilst those in the pudendal and superior and inferior gluteal nerves accompany the same named arteries to the gluteal and perineal tissues. Branches may also supply the pelvic lymph nodes.

Body_ID: P108084

Preganglionic fibres for the rest of the lower limb are derived from the lower three thoracic and upper two or three lumbar spinal segments. They reach the lower thoracic and upper lumbar ganglia through white rami communicantes and descend through the sympathetic trunk to synapse in the lumbar ganglia. Postganglionic fibres pass from these ganglia via grey rami communicantes to the femoral nerve which carries them to the distribution of the femoral artery and its branches. Some fibres descend through the lumbar ganglia to synapse in the upper two or three sacral ganglia, from which postganglionic axons join the tibial nerve to supply the popliteal artery and its branches in the leg and foot.

Body_ID: P108085

Sympathetic denervation of vessels in the lower limb can be effected by removing or ablating the upper three lumbar ganglia and the intervening parts of the sympathetic trunk, which is rarely useful in treating vascular insufficiency of the lower limb.

Body_ID: P108086

© 2008 Elsevier