Lesser pelvis and perineum

Lesser Pelvis

The lesser pelvis is a bowl-shaped structure formed from the sacrum, pubis, ilium, ischium, the ligaments that interconnect these bones, and the muscles that line their inner surfaces. It begins at the level of the plane passing through the promontory of the sacrum, the arcuate line of the ilium, the pecten pubis 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; the bony structures above it are sometimes referred to as the greater pelvis. They form part of the walls of the lower abdomen. In children, the width of the pelvic inlet is an age-independent predictor of chest width and thoracic dimensions ( ). The ischiopubic synchondrosis is the temporary cartilage formed between the pubis and ischium prior to the completion of ossification around 12 years of age ( ). The ‘outlet’ of the lesser pelvis is formed by the ischiopubic rami, ischial tuberosities, sacrotuberous ligaments and distal sacrum. The bones surround a central pelvic canal that forms an anteriorly concave curve (the curve of Carus); in the female, it constitutes the birth canal. The topography of the bony and ligamentous pelvis is considered in full detail in Chapter 77 .

Muscles and fasciae

Pelvic muscles

The muscles arising within the pelvis form two groups. Piriformis and obturator internus form part of the walls of the pelvis and are considered primarily as muscles of the lower limb ( Fig. 71.1 ). Levator ani and ischiococcygeus form the pelvic diaphragm and delineate the inferior limit of the lesser pelvis ( Fig. 71.2 ). The fasciae investing the muscles are continuous with visceral pelvic fascia superiorly, perineal fascia inferiorly and obturator fascia laterally.

Fig. 71.2, Muscles of the female pelvis. The superior gluteal and obturator vessels and nerves, and the pelvic viscera, have been omitted for clarity.

Piriformis

Piriformis forms part of the posterolateral wall of the lesser pelvis and 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 superior part of the pelvic surface of the sacrotuberous ligament. It passes out of the pelvis through the greater sciatic foramen superior to the sacrospinous ligament. Within the pelvis, the posterior surface of this muscle lies against the sacrum, and its anterior surface is related to the rectum (especially on the left), the sacral plexus and branches of the internal iliac vessels. Piriformis is described in more detail in Chapter 77 .

Obturator internus

Obturator internus and its fascia form part of the anterolateral wall of the lesser pelvis. These attach to the structures surrounding the obturator foramen, ischiopubic ramus, the pelvic surface of the hip bone inferior and posterior to the linea terminalis, and the superior part of the greater sciatic foramen. These structures are also attached to the medial part of the pelvic surface of the obturator membrane. Specialized portions of the obturator fascia give attachment to some of the fibres of levator ani (tendinous arch of levator ani), so that only the superior portion of obturator internus can be seen from above. The inferior portion forms part of the boundaries of the ischio-anal fossa. In the male, the superior portion lies lateral to the urinary bladder, the obturator and vesical vessels, and the obturator nerve. In the female, the attachments of the broad ligament of the uterus, the distal end of the uterine tubes and the uterine vessels also lie medial to obturator internus and its fascia.

Levator ani (pubococcygeus, iliococcygeus and pubo-analis)

Levator ani is a broad muscular sheet of variable thickness attached to the internal surface of the pelvis. It forms a large portion of the pelvic diaphragm ( Fig. 71.3 ) ( ). The muscle is subdivided into named portions according to their attachments and the pelvic viscera to which they are related (pubococcygeus, iliococcygeus and pubo-analis). These parts are often referred to as separate muscles but the boundaries between them cannot easily be distinguished; moreover, they perform many similar physiological functions. Pubococcygeus is often subdivided into separate parts according to the pelvic viscera to which each part relates (e.g. puboprostaticus, pubovaginalis). Levator ani arises from each side of the walls of the pelvis along the condensation of the obturator fascia (the tendinous arch of levator ani). Fibres from ischiococcygeus attach to the sacrum and coccyx but the remaining parts of the muscle converge in the midline. Fibres from iliococcygeus join via a partly fibrous intersection and form the iliococcygeal raphe posterior to the anorectal junction. Closer to the anorectal junction, and elsewhere in the pelvic diaphragm, the fibres are nearly continuous with those of the opposite side, such that the muscle forms a sling (iliococcygeus and pubo-analis).

Fig. 71.3, Muscles of the female pelvis viewed from above. The anorectal junction, vagina and urethra have been divided at the level of the pelvic diaphragm.

Attachments

The attachments for pubococcygeus, iliococcygeus and pubo-analis are as follows.

Pubococcygeus

Pubococcygeus originates from the posterior aspect of the body of the pubis and passes posteriorly almost horizontally. Its most medial fibres run directly lateral to the urethra and its sphincter as it passes through the pelvic diaphragm; here, the muscle is correctly called puboperinealis, although it is often referred to as pubo-urethralis because of its juxtaposition to the proximal half of the urethra in both sexes, however, no direct connection with the urethra is present. In males, some of these fibres lie lateral and inferior to the prostate and are referred to as puboprostaticus. In females, fibres run further back and attach to the lateral walls of the vagina, where they are referred to as pubovaginalis. In both sexes, fibres from this part of pubococcygeus attach to the perineal body; a few elements also attach to the anorectal junction. Some fibres 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, other fibres of pubococcygeus form a tendinous intersection as part of the anococcygeal raphe.

Iliococcygeus

Iliococcygeus is attached to the inner surface of the ischial spine inferior and anterior to the attachment of ischiococcygeus, and also to the tendinous arch of levator ani as far anteriorly as the obturator canal (see Fig. 71.2 ). The most posterior fibres are attached to the apex of the sacrum and coccyx, but the majority join fibres from the contralateral side to form a raphe that is effectively continuous with the fibroelastic anococcygeal ligament, which is closely applied to its inferior surface; some muscle fibres may attach into the ligament. The raphe provides a strong attachment for the pelvic diaphragm posteriorly and must be divided to allow wide excisions of the anorectal canal to be performed during abdominoperineal excisions for malignancy. An accessory slip sometimes arises from the most posterior part and is referred to as iliosacralis.

Pubo-analis

Pubo-analis lies lateral to pubococcygeus and cannot be seen from inside the pelvis. It originates from the inner surface of the ischiopubic rami immediately adjacent to, and sometimes partly arising from, the perineal membrane. Its fibres pass lateral to those of iliococcygeus and pubococcygeus to decussate posterior to the rectum at the anorectal junction. The border between pubo-analis and some fibres of the external anal sphincter is indistinct.

Ischiococcygeus

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

Relations

The superior, pelvic surface of levator ani is separated only by fascia (superior pelvic diaphragmatic, visceral and extraperitoneal) from the urinary bladder, prostate or uterus and vagina, rectum and peritoneum. Its inferior, perineal surface forms the medial wall of the ischio-anal fossa and the superior wall of the anterior recess of the fossa, both being covered by the inferior fascia of the pelvic diaphragm. The posterior border is separated from the coccyx by areolar tissue. The medial borders of the two levator muscles and the inferior ischiopubic rami border the levator hiatus, through which pass the urethra, vagina (in the female) and anus. In the female, that portion of the hiatus that lies anterior to the perineal body is referred to as the urogenital hiatus.

Vascular supply

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

Innervation

The nerves to levator ani originate mainly from the third and fourth sacral ventral (anterior) rami, with lesser contributions from the second sacral ventral ramus. These nerves enter the pelvis just above ischiococcygeus, sometimes piercing it, to pass along the anterior surface of ischiococcygeus and pubococcygeus, supplying these muscles and sending fibres to pubo-analis ( ). The pudendal nerve can also supply pubococcygeus from its lateral surface through its inferior anal and perineal branches.

Actions

Pubococcygeus and pubo-analis pull the pelvic and perineal structures anteriorly and superiorly, occluding the levator hiatus. In the female, this action occludes the vagina and prevents prolapse of the pelvic organs through the urogenital hiatus. The constant baseline activity of levator ani is similar to that of the external anal sphincter, modulated to adjust to the loads placed on them. The action of pubo-analis and pubococcygeus also reinforces the external anal sphincter and helps to create the anorectal angle. Iliococcygeus and to a lesser extent the less muscular ischiococcygeus form a relatively horizontal diaphragm, especially in the posterior half of the pelvis, that assists pubo-analis in achieving bowel and bladder continence.

Levator ani must relax appropriately to permit expulsion of urine and, particularly, faeces; it contracts with the abdominal muscles and the respiratory diaphragm to raise intra-abdominal pressure. It forms much of the muscular pelvic diaphragm, which supports the pelvic viscera. Like the respiratory diaphragm, but unlike the abdominal muscles, levator ani is also active in the inspiratory phase of quiet respiration. In pregnancy, the shape of the pelvic diaphragm can help to direct the fetal head into the anteroposterior diameter of the pelvic outlet.

Pelvic fasciae

It is convenient to divide the pelvic fasciae into the parietal pelvic fascia, which forms the coverings of the pelvic muscles, and the visceral pelvic fascia, which forms the coverings of the pelvic organs and their neurovascular supply ( Fig. 71.4 ).

Fig. 71.4, Fasciae of the male pelvis and perineum: median sagittal section. The visceral parietal fasciae have been omitted for clarity.

Parietal pelvic fascia

The parietal pelvic fascia consists of the obturator fascia, piriformis fascia, superior fascia over the pelvic diaphragm and the presacral fascia.

Obturator fascia

The parietal pelvic fascia on the pelvic (medial) surface of obturator internus is well differentiated. In humans, anterior to the lateral attachment of the pelvic organs, a portion of it is derived from the degenerated superior portion of the attachment of levator ani. 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 posterior aspect of the pubis. Behind the obturator canal, the fascia is markedly aponeurotic and gives a firm attachment to the iliococcygeus, usually called the tendinous arch of levator ani (see Figs 71.3, 71.14–71.15 ). Superior to the attachment of levator ani, the fascia is thin and effectively comprises only the epimysium of the muscle and overlying connective tissue; posteriorly, it forms part of the lateral wall of the ischio-anal fossa in the perineum; anteriorly, it merges with the fasciae of the muscles of the deep perineal space, which is continuous with the ischio-anal fossa. The obturator fascia is continuous with the periosteum of the hip bone and piriformis fascia.

Fascia over piriformis

The fascia over the internal surface of piriformis is very thin and fuses with the periosteum on the anterior sacrum at the margins of the anterior sacral foramina. It ensheathes the ventral rami that emerge from these foramina so that the nerves are often described as lying behind the fascia. The internal iliac vessels lie in front of the piriformis fascia and their branches draw out sheaths of the fascia and extraperitoneal tissue into the gluteal region, superior and inferior to piriformis.

Fascia over levator ani

Both surfaces of levator ani have a fascial covering: the combination of the two fascial layers and the intervening muscle is called the pelvic diaphragm. On the inferior surface, the fascia is continuous with the obturator fascia below the tendinous arch of levator ani laterally. It covers the medial wall of the ischio-anal fossa and blends below with fasciae on the external urethral sphincter and the external anal sphincter. The superior fascia of the pelvic diaphragm is markedly thicker than the inferior fascia and is attached anteriorly to the posterior aspect of the body of the pubis, approximately 2 cm superior to its inferior border. It extends laterally across the superior pubic ramus, blending with the obturator fascia and continuing along an irregular line to the ischial spine. It is continuous posteriorly with the piriformis fascia and the anterior sacrococcygeal ligament. Medially, the superior fascia of the pelvic diaphragm blends with the visceral pelvic fascia to contribute to the endopelvic fascia.

Tendinous arch of the pelvic fascia

Low on the superomedial aspect of the superior fascia of the pelvic diaphragm, a thick white band of condensed connective tissue extends from the inferior part of the pubic symphysis to the superior margin of the ischial spine. It provides attachment for the condensations of visceral pelvic fasciae that provide support to the urethra and urinary bladder, and to the vagina in females (see below).

Presacral fascia

The presacral fascia forms a hammock-like structure behind the posterior portion of the mesorectal fascia. Laterally, it extends to the origin of the piriformis fascia and the superior fascia of the pelvic diaphragm, with which it blends; more inferiorly, it extends between the white line of the parietal pelvic fascia on either side. Inferiorly, it extends to the anorectal junction, where it fuses with the posterior aspect of the mesorectal fascia and the iliococcygeal raphe at the level of the anorectal junction. Superiorly, it can be traced to the origin of the superior hypogastric plexus, where it thins progressively over the sacral promontory and becomes continuous with the retroperitoneal tissues. The right and left hypogastric nerves and inferior hypogastric plexuses lie on its surface. It forms a distinct layer that can be seen both on magnetic resonance imaging (MRI) of the pelvis and during surgery. The presacral fascia provides an important landmark because extension of rectal tumours through it significantly reduces the possibility of curative resectional surgery. Dissection in the plane posterior to the fascia can result in bleeding from the presacral veins. The adventitia of the veins is partly attached to the posterior surface of the fascia, which means that the haemorrhage can be severe (because the veins are unable to contract properly). The presacral fascia is a useful structure to which the rectum can be sutured during rectopexy for rectal prolapse.

Visceral pelvic fascia

The urogenital organs in both sexes are connected bilaterally to the pelvic walls by neurovascular mesenteric condensations ensheathed by a meshwork of loose connective and adipose tissues and lying above the perineal membrane ( ). The lateral attachments of the pelvic organs to the pelvic side walls are referred to as the endopelvic fascia. Considered as a unit, the connections provide a conduit for neurovascular elements passing from the pelvic side wall to the organs and serve as attachments that help to retain the pelvic organs in place, playing an important role in preventing pelvic organ prolapse in females ( ). They are associated with loose connective tissue that extends to the midline, separating the bladder from the vagina and the vagina from the rectum in the female, and separating the bladder, prostate and seminal glands from the rectum in the male. The fasciae contain different amounts of connective tissue and smooth muscle: where they are either unusually dense or form visible ridges, they are called ‘ligaments’ (e.g. cardinal ligament, uterosacral ligament). Clinically, these lateral attachments are often referred to as visceral ‘ligaments’, but they are quite unlike the bands of dense, regular connective tissue that typify skeletal ligaments. Their lateral attachments sweep off the pelvic walls, arising from the superior fascia over levator ani and from part of the piriformis fascia more superiorly and posteriorly. The ligaments passing to the urinary bladder in the male, or the bladder and proximal vagina and uterus in the female, are relatively long, but these lateral connections become shorter towards the pelvic outlet, until at the level of the perineal membrane there is a direct connection between the organs and the pelvic walls.

In the female, the cardinal ligament surrounds the uterovaginal junction and extends distally to mid-vagina, where the vagina has a more direct lateral attachment at the tendinous arch of the pelvic fascia. The portions that attach to the uterus and vagina are sometimes called the parametrium and paracolpium, respectively. Further accounts of the paravisceral portions of the visceral pelvic fascia are given in the chapters describing the organs to which the fascia relates. The uterosacral ligament is a visible fold of tissue flanking the rectum as it descends posterior to the cervix in the female. It contains a considerable amount of smooth muscle near its attachment to the cervix and some of the pelvic autonomic nerves. A similar vesicosacral fold is present in the male.

Approximately 1 cm above the inferior border of the pubis and 1 cm lateral to the midline, a band of dense pelvic connective tissue, the anterior end of the tendinous arch of the pelvic fascia, is attached to either the paravaginal (female) or the prostatic (male) tissues. This band extends on the inner surface of levator ani and joins the tendinous arch of levator ani to the ischium, just above the ischial spine. The attachment of the paravaginal tissue to the pubis is sometimes called the pubo-urethral ligament, a misnomer because it is not attached to the urethra. The attachment of the anterior vaginal wall to the tendinous arch of the pelvic fascia, the paravaginal attachment, helps to provide support to the vagina, urethra and urinary bladder.

There is much less condensation of connective tissue around the rectum. A layer presumed to be a peritoneal fusion fascia is described between the rectum and either the seminal glands in the male or the vagina in the female (the rectovesical septum or rectovaginal septum, respectively): it is not connected to the rectum. The connective tissue over the longitudinal muscles of the rectum is thickened just superior to the point where it traverses levator ani and fuses with the endopelvic fascia and the anococcygeal ligament, forming a structure that is sometimes referred to as a rectosacral ligament.

Vascular supply and lymphatic drainage

The lesser pelvis contains the internal iliac arteries and veins, and the lymphatics that drain most of the pelvic viscera. The common and external iliac vessels and the lymphatics that drain the lower limb lie along the linea terminalis and in the lower retroperitoneum, but are conveniently discussed together with the vessels of the lesser pelvis. There is remarkable variation in the terminal branching pattern for the iliac vessels and no two individuals have quite the same anatomy. However, there are general patterns, and the following description will consider the common pattern.

Arteries

Common iliac artery

The abdominal aorta bifurcates into the right and left common iliac arteries anterolateral to the left side of the body of the fourth lumbar vertebra ( ). These arteries diverge as they descend and they divide at the level of the sacroliac joint into external and internal iliac arteries. The external iliac artery is the principal artery of the lower limb. The internal iliac artery provides the principal supply to the walls and viscera of the pelvis, the perineum and the gluteal region.

Right common iliac artery

The right common iliac artery is approximately 5 cm long. It passes obliquely across part of the bodies of the fourth and the fifth lumbar vertebrae, and is crossed anteriorly by the sympathetic rami to the pelvic plexus and, at its division into internal and external iliac arteries, by the ureter. It is covered by the parietal peritoneum, which separates it from the small intestine. Posteriorly, it is separated from the bodies of the fourth and fifth lumbar vertebrae and the intervening intervertebral 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. Laterally, the inferior vena cava and the right common iliac vein lie superiorly and the right psoas major lies inferiorly. The left common iliac vein is medial to the proximal part of the right common iliac artery.

Left common iliac artery

The left common iliac artery is shorter than the right and is approximately 4 cm long. Lying anteriorly are branches of the sympathetic trunk that contribute to the superior hypogastric plexus, the superior anorectal artery and, at its terminal bifurcation, the ureter. The sympathetic trunk, the bodies of the fourth and fifth lumbar vertebrae and the intervening intervertebral disc, the obturator nerve, lumbosacral trunk and iliolumbar artery are all posterior. The left common iliac vein is posteromedial and the left psoas major is lateral.

Branches

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

Internal iliac artery

Each internal iliac artery is approximately 4 cm long and begins at the common iliac bifurcation, level with the lumbosacral intervertebral disc and anterior to the sacroiliac joint ( Figs 71.5–71.6 ). It descends posteriorly to the superior margin of the greater sciatic foramen, where it divides into an anterior division, which continues in the same line towards the ischial spine, and a posterior division, which passes back to the greater sciatic foramen. The anterior division primarily supplies the pelvic organs, while the posterior division primarily supplies muscles in the hip and back. The ureter and, in females, the ovary and distal end of the uterine tube, are anterior to the artery. The internal iliac vein, lumbosacral trunk and sacroiliac joint are posterior. Laterally are the external iliac vein, between the artery and psoas major, and the obturator nerve lying inferior to the vein. Medially, the parietal peritoneum and tributaries of the internal iliac vein separate the artery from the terminal ileum on the right and the sigmoid colon on the left. For details of the considerable variation in the anatomy of the internal iliac artery see .

Fig. 71.5, A , Arteries of the male pelvis. B , Volume-rendered CT angiogram of a male pelvis. Left anterior oblique view of the right hemipelvis showing branches of the internal iliac artery. The vesical and middle anorectal branches of the anterior division are too small to be visualized.

In the fetus, the internal iliac artery is twice the size of the external iliac artery 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, and 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 and the remainder becomes a fibrous medial umbilical ligament. Persistence of the umbilical artery has been described and can cause extrinsic obstruction of the distal ureter ( ). In males, the patent part (commonly, the superior vesical artery) usually gives off the artery to the ductus deferens.

Posterior division branches

The branches of the posterior division of the internal iliac artery are the iliolumbar, lateral sacral and superior gluteal arteries.

Iliolumbar artery

The iliolumbar artery is the first branch of the posterior division of the internal iliac artery and ascends laterally anterior to the sacroiliac joint and lumbosacral 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 radicular branches to 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 run around the iliac crest, contribute to the supply of gluteal and abdominal muscles, and anastomose with the superior gluteal, circumflex iliac and lateral circumflex femoral arteries (see Fig. 76.4 ).

Lateral sacral arteries

The lateral sacral arteries are usually double. If they are single, they soon divide into superior and inferior branches. The superior and larger branch passes medially into the first or second anterior sacral foramen, supplies the sacrum and contents of the sacral canal, and then leaves the sacrum via the corresponding posterior foramen to supply the skin and muscles posterior to the sacrum. The inferior branch crosses obliquely anterior to piriformis and the sacral anterior rami, and 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 in the same way as the branches of the superior artery.

Superior gluteal artery

The superior gluteal artery is the largest branch of the internal iliac artery and effectively forms the main continuation of its posterior division. It runs posteriorly between the lumbosacral trunk and the first sacral ventral ramus, or between the first and second sacral ventral rami, and then turns slightly inferiorly, leaving the pelvis via 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 (see Fig. 77.47 ), 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 ilium, 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; other branches run through gluteus minimus to supply the hip joint.

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

Anterior division branches

The branches of the anterior division of the internal iliac artery are the superior and inferior vesical, middle anorectal, vaginal, obturator, uterine, internal pudendal and inferior gluteal arteries (see Fig. 71.6 ). There is significant variation in the branching patterns of the anterior division and therefore only the general principles will be considered here.

Fig. 71.6, A , Arteries of the female pelvis. B , Volume-rendered CT angiogram of a female pelvis. Left anterior oblique view of the right hemipelvis showing branches of the internal iliac artery. The vesical and inferior anorectal branches of the anterior division are too small to be visualized. Note that the middle gluteal artery arises from the posterior division as a variant.

Superior vesical artery

The superior vesical artery is the first large branch of the anterior division. It lies on the lateral wall of the pelvis, just inferior to the linea terminalis, and runs anteroinferiorly, medial to the periosteum of the posterior surface of the pubis. It supplies the distal end of the ureter, the urinary bladder, the proximal end of the ductus deferens and the seminal glands. It also gives origin to the umbilical artery in the fetus, 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.

Inferior vesical artery

The inferior vesical artery sometimes arises as a common branch with the middle anorectal artery. It supplies the urinary bladder, prostate, seminal glands and ductus deferens in the male, and the urinary bladder in the female, where it is often replaced by the vaginal artery. identified this vessel in roughly one half of females.

Middle anorectal artery

The middle anorectal artery runs into the lateral fascial coverings of the mesorectum. It often consists of multiple branches, can be small, and occasionally arises either close to or in common with the origin of the inferior vesical artery in males.

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