Pelvis and Peritoneum Chapter PDF

Introduction Listen The pelvis (L. basin) is the part of the trunk inferoposterior to the abdomen and is the area of transition between the trunk and the lower limbs (Fig. 6.1). The pelvic cavity is a continuation of the abdominal cavity into the pelvis through the pelvic inlet. The perineal region...

Introduction Listen The pelvis (L. basin) is the part of the trunk inferoposterior to the abdomen and is the area of transition between the trunk and the lower limbs (Fig. 6.1). The pelvic cavity is a continuation of the abdominal cavity into the pelvis through the pelvic inlet. The perineal region refers to the area of the trunk between the thighs and the buttocks, extending from the pubis to the coccyx. The perineum is a shallow compartment lying deep to this area and inferior to the pelvic diaphragm. FIGURE 6.1. View OriginalDownload Slide (.ppt) Thoracic and abdominopelvic cavity. A and B. The pelvis is the space within the pelvic girdle, overlapped externally by the abdominal and gluteal (lower limb) regions and the perineum. Thus, the pelvis has no unique external surface area. Pelvis Listen The superior boundary of the pelvic cavity is the pelvic inlet, the superior pelvic aperture (Figs. 6.1 and 6.2). The pelvis is limited inferiorly by the pelvic outlet, which is bounded anteriorly by the pubic symphysis (L. symphysis pubis) and posteriorly by the coccyx. FIGURE 6.2. View OriginalDownload Slide (.ppt) Bony pelvis. A. Articulated pelvis. B. Child’s right hip bone. C. Adult’s right hip bone. In the anatomical position, the anterior superior iliac spine and the anterior aspect of the pubis lie in the same vertical plane. The pelvic inlet (superior pelvic aperture) is bounded by the linea terminalis of the pelvis, which is formed by the ● ● superior margin of the pubic symphysis anteriorly ● ● posterior border of the pubic crest ● ● pecten pubis, the continuation of the superior ramus of the pubis, which forms a sharp ridge ● ● arcuate line of the ilium ● ● anterior border of the ala (L. wing) of the sacrum ● ● sacral promontory The pelvic outlet (inferior pelvic aperture) is bounded by the ● ● inferior margin of the pubic symphysis anteriorly ● ● inferior rami of the pubis and ischial tuberosities anterolaterally ● ● sacrotuberous ligaments posterolaterally (Fig. 6.3B) ● ● tip of the coccyx posteriorly FIGURE 6.3. View OriginalDownload Slide (.ppt) Ligaments of pelvic girdle. Pelvic Girdle The pelvic girdle is a basin-shaped ring of bones that surrounds the pelvic cavity and connects the vertebral column to the two femurs in the thighs. The main functions of the strong pelvic girdle are to (1) transfer the weight of the upper body from the axial to the lower appendicular skeleton for standing and walking, (2) to withstand compression and other forces resulting from its support of body weight, and (3) house and protect the pelvic viscera (including the gravid uterus). In mature individuals, the pelvic girdle is formed by the three bones of the bony pelvis (Fig. 6.2 and Table 6.1): ● ● Right and left hip bones: Two large, irregularly shaped bones, each of which forms at puberty by fusion of three bones—ilium, ischium, and pubis ● ● Sacrum: Formed by the fusion of five, originally separate, sacral vertebrae TABLE 6.1. Comparison of Male and Female Bony Pelves Bony Pelvis Male (♂) Female (♀) General structure Thick and heavy Thin and light Greater pelvis (pelvis major) Deep Shallow Lesser pelvis (pelvis minor) Narrow and deep Wide and shallow Pelvic inlet (superior pelvic aperture) Heart-shaped Oval or rounded Pelvic outlet (inferior pelvic aperture) Comparatively small Comparatively large Pubic arch and subpubic angle (degree) Narrow (<70 degrees) Wide (>80 degrees) Obturator foramen Round Oval Acetabulum Large Small The hip bones are joined at the pubic symphysis anteriorly and to the sacrum posteriorly at the sacro-iliac joints to form a bony ring, the pelvic girdle. The ilium is the superior, flattened, fan-shaped part of the hip bone (Fig. 6.2). The ala of the ilium represents the spread of the fan, and the body of the ilium, the handle of the fan. The body of the ilium forms the superior part of the acetabulum, the cup-shaped depression on the external surface of the hip bone with which the head of the femur articulates. The iliac crest, the rim of the ilium, has a curve that follows the contour of the ala between the anterior and the posterior superior iliac spines. The anterior concave part of the ala forms the iliac fossa. The ischium has a body and a ramus (L. branch). The body of the ischium forms the posterior part of the acetabulum, and the ramus forms the posterior part of the inferior boundary of the obturator foramen. The large postero-inferior protuberance of the ischium is the ischial tuberosity (Fig. 6.2). The small, pointed posterior projection near the junction of the ramus and body is the ischial spine. The pubis is an angulated bone that has the superior pubic ramus, which forms the anterior part of the acetabulum, and the inferior pubic ramus, which forms the anterior part of the inferior boundary of the obturator foramen. The superior pubic ramus has an oblique ridge, the pecten pubis (pectineal line of pubis), on its superior aspect. A thickening on the anterior part of the body of the pubis is the pubic crest, which ends laterally as a swelling—the pubic tubercle (Fig. 6.3A). The pubic arch is formed by the ischiopubic rami (conjoined inferior rami of the pubis and ischium) of the two sides. These rami meet at the pubic symphysis, and their inferior borders define the subpubic angle (the distance between the right and the left ischial tuberosities), which can be approximated by the angle between the abducted middle and index fingers for the male, and the angle between the index finger and extended thumb for the female (Fig. 6.4). FIGURE 6.4. View OriginalDownload Slide (.ppt) Comparison of pelvic girdles of male and female. The bony pelvis is divided into greater (false) and lesser (true) pelves by the oblique plane of the pelvic inlet (superior pelvic aperture) (Figs. 6.1 and 6.2). The greater pelvis (L. pelvis major) is ● ● superior to the pelvic inlet ● ● bounded by the abdominal wall anteriorly, the ala of ilium laterally, and the L5 and S1 vertebrae posteriorly ● ● the location of some abdominal viscera, such as the sigmoid colon and some loops of ileum The lesser pelvis (L. pelvis minor) is ● ● between the pelvic inlet and the pelvic outlet (Fig. 6.3B) ● ● the location of the pelvic viscera—urinary bladder and reproductive organs, such as the uterus and ovaries ● ● bounded by the pelvic surfaces of the hip bones, sacrum, and coccyx ● ● limited inferiorly by the musculomembranous pelvic diaphragm (levator ani) (Table 6.2 and Fig. 6.1B) TABLE 6.2. Peritoneal Reflections in Pelvis Female (Parts A and B)a Male (Part C)a 1 Descends anterior abdominal wall (loose attachment allows insertion of bladder as it fills) 1 Descends anterior abdominal wall (loose attachment allows insertion of bladder as it fills) 2 Reflects onto superior surface of bladder, creating supravesical fossa 2 Reflects onto superior surface of bladder, creating supravesical fossa 3 Covers convex superior surface of bladder; slopes down sides of bladder to ascend lateral wall of pelvis, creating paravesical fossae on each side 3 Covers convex superior surface (roof) of bladder, sloping down sides of roof to ascend lateral wall of pelvis, creating paravesical fossae on each side 4 Reflects from bladder to body of uterus, forming vesico-uterine pouch 4 Descends posterior surface of bladder as much as 2 cm 5 Covers body and fundus of uterus, posterior fornix of vagina; extends laterally from uterus as double fold of mesentery, the broad ligament that engulfs uterine tubes, and round ligaments of uterus, and suspends ovaries 5 Laterally, forms fold over ureters (ureteric fold), ductus deferentes, and superior ends of seminal glands 6 Reflects from vagina onto rectum, forming recto-uterine pouchb (pouch of Douglas) 6 Reflects from bladder and seminal glands onto rectum, forming rectovesical pouchb 7 Recto-uterine pouch extends laterally and posteriorly to form pararectal fossae on each side of rectum. 7 Rectovesical pouch extends laterally and posteriorly to form pararectal fossae on each side of rectum. 8 Ascends rectum; from inferior to superior, rectum is subperitoneal and then retroperitoneal. 8 Ascends rectum; from inferior to superior, rectum is subperitoneal and then retroperitoneal. 9 Engulfs sigmoid colon beginning at rectosigmoid junction 9 Engulfs sigmoid colon beginning at rectosigmoid junction aNumbers bLow refer to Figure 6.6. point of peritoneal cavity in erect position. CLINICAL BOX Sexual Differences in Bony Pelves The male and female bony pelves differ in several respects (Fig. 6.4 and Table 6.1). These sexual differences are related mainly to the heavier build and larger muscles of men and to the adaptation of the pelvis, particularly the lesser pelvis, in women for childbearing. Hence, the male pelvis is heavier and thicker than the female pelvis and usually has more prominent bone markings. In contrast, the female pelvis is wider and shallower and has a larger pelvic inlet and outlet. The shape and size of the pelvic inlet are significant because it is through this opening that the fetal head enters the lesser pelvis during labor. To determine the capacity of the pelvis for childbirth, the diameters of the lesser pelvis are noted during a pelvic examination or using imaging. The minimum anteroposterior diameter of the lesser pelvis, the true (obstetrical) conjugate from the middle of the sacral promontory to the posterosuperior margin of the pubic symphysis, is the narrowest fixed distance through which the baby’s head must pass in a vaginal delivery. However, this cannot be measured directly during a pelvic exam. Consequently, the diagonal conjugate is measured by palpating the sacral promontory with the tip of the middle finger, using the other hand to mark the level of the inferior margin of the pubic symphysis on the examining hand. After the examining hand is withdrawn, the distance between the tip of the index finger (1.5 cm shorter than the middle finger) and the marked level of the pubic symphysis is measured to estimate the true conjugate, which should be 11 cm or greater. Pelvic Fractures Pelvic fractures can result from direct trauma to the pelvic bones, such as may occur during an automobile accident, or from forces transmitted to these bones from the lower limbs during falls on the feet. Pelvic fractures may cause injury to pelvic soft tissues, blood vessels, nerves, and organs. Joints and Ligaments of Pelvic Girdle The primary joints of the pelvis are the sacro-iliac joints and the pubic symphysis, which link the skeleton of the trunk and the lower limb (Fig. 6.2A). The lumbosacral and sacrococcygeal joints are directly related to the pelvic girdle. Strong ligaments support and strengthen these joints (Fig. 6.3). Sacro-Iliac Joints The sacro-iliac joints are strong, weight-bearing, compound joints consisting of an anterior synovial joint (between the ear-shaped auricular surfaces of the sacrum and ilium covered with articular cartilage) and a posterior syndesmosis (between the tuberosities of the same bones) (Figs. 6.2C and 6.5). The articular (auricular) surfaces of the synovial joint have irregular but congruent elevations and depressions that interlock. The sacro-iliac joints differ from most synovial joints in that they have limited mobility, a consequence of their role in transmitting the weight of most of the body to the hip bones. FIGURE 6.5. View OriginalDownload Slide (.ppt) Sacro-iliac joints and ligaments. A. Posterior half of coronally sectioned pelvis. B. Articular surfaces of sacro-iliac joint. C. Role of sacrotuberous and sacrospinous ligaments in resisting anterior rotation of pelvis. D. Pubic symphysis. D Courtesy of Dr. E.L. Lansdown, University of Toronto, Ontario, Canada. The sacrum is suspended between the iliac bones and is firmly attached to them by posterior and interosseous sacro-iliac ligaments. The thin anterior sacro-iliac ligaments form the anterior part of the fibrous capsule of the synovial joint. The interosseous sacro-iliac ligaments occupy an area of about 10 cm2 each and are the primary structures involved in transferring the weight of the upper body from the axial skeleton to the two ilia and then to the femurs during standing and to the ischial tuberosities during sitting. The posterior sacro-iliac ligaments are posterior external continuations of the interosseous sacro-iliac ligaments. Usually, movement is limited to slight gliding and rotary movements, except when subject to considerable force such as occurs after a high jump (or during late pregnancy—see next Clinical Box). Then, the weight of the body is transmitted through the sacrum anterior to the rotation axis, tending to push the superior sacrum inferiorly, thereby causing the inferior sacrum to rotate superiorly. This tendency is resisted by the strong sacrotuberous and sacrospinous ligaments (Fig. 6.3). These ligaments allow only limited upward movement of the inferior end of the sacrum, thus providing resilience to the sacro-iliac region when the vertebral column sustains sudden weight increases (Fig. 6.5C). Pubic Symphysis The pubic symphysis is a secondary cartilaginous joint that is formed by the union of the bodies of the pubic bones in the median plane (Figs. 6.3 and 6.5D). The fibrocartilaginous interpubic disc is generally wider in women than in men. The ligaments joining the pubic bones are thickened superiorly and inferiorly to form the superior pubic ligament and the inferior (arcuate) pubic ligament, respectively. The decussating fibers of tendinous attachments of the rectus abdominis and external oblique muscles also strengthen the pubic symphysis anteriorly. Lumbosacral Joints The L5 vertebra and sacrum articulate anteriorly at the anterior intervertebral (IV) joint, formed by the L5–S1 IV disc between their bodies posteriorly (Fig. 6.3A) and at two zygapophysial joints (facet joints) between the articular processes of these bones (Fig. 6.3B). The superior articular facets on the sacrum face posteromedially, interlocking with the anterolaterally facing inferior articular facets of the L5 vertebra, preventing L5 from sliding anteriorly. Iliolumbar ligaments unite the transverse processes of L5 to the ilia. Sacrococcygeal Joint The sacrococcygeal joint is a secondary cartilaginous joint with an IV disc. Fibrocartilage and ligaments join the apex of the sacrum to the base of the coccyx (Fig. 6.3A). The anterior and posterior sacrococcygeal ligaments are long strands that reinforce the joint, much like the anterior and posterior longitudinal ligaments do for superior vertebrae. CLINICAL BOX Relaxation of Pelvic Ligaments and Increased Joint Mobility during Pregnancy During pregnancy, the pelvic joints and ligaments relax, and pelvic movements increase. This relaxation during the latter half of pregnancy is caused by the increase in levels of the sex hormones and the presence of the hormone relaxin. The sacro-iliac interlocking mechanism is less effective because the relaxation permits greater rotation of the pelvis and contributes to the lordotic posture often assumed during pregnancy with the change in the center of gravity. Relaxation of the sacro-iliac joints and pubic symphysis permits as much as a 10–15% increase in diameters (mostly transverse), facilitating passage of the fetus through the pelvic canal. The coccyx is also allowed to move posteriorly. Peritoneum and Peritoneal Cavity of Pelvis The peritoneum lining the abdominal cavity continues into the pelvic cavity, reflecting onto the superior aspects of most pelvic viscera (Fig. 6.6 and Table 6.2). Only the uterine tubes—except for their ostia, which are open—are intraperitoneal and suspended by a mesentery. The ovaries, although suspended in the peritoneal cavity by a mesentery, are not covered with peritoneum. The peritoneum creates a number of folds and fossae as it reflects onto most of the pelvic viscera. FIGURE 6.6. View OriginalDownload Slide (.ppt) Pelvic peritoneum. The peritoneum is not firmly bound to the suprapubic crest, allowing the bladder to expand between the peritoneum and the anterior abdominal wall as it fills. Walls and Floor of Pelvic Cavity The pelvic cavity has an antero-inferior wall, two lateral walls, and a posterior wall. Muscles of the pelvic walls are summarized in Figure 6.7A–E and Table 6.3. The antero-inferior pelvic wall ● ● is formed primarily by the bodies and rami of the pubic bones and the pubic symphysis ● ● participates in bearing the weight of the urinary bladder FIGURE 6.7. View OriginalDownload Slide (.ppt) View OriginalDownload Slide (.ppt) Muscles of pelvic walls and floor. A. Superior surface of the pelvic diaphragm. B. Coronal section of pelvis through levator ani and rectum. C. Inferior surface of pelvic diaphragm. D. Muscles of lesser pelvis. E. Levator ani added to D.PS, pubic symphysis. TABLE 6.3. Muscles of Pelvic Walls and Floor Muscle Proximal Attachment Distal Attachment Innervatio n Main Action Levator ani (pubococcygeus and iliococcygeus) Body of pubis, tendinous arch of levator ani, ischial spine Perineal body, coccyx, anococcygea l ligament, walls of prostate or vagina, rectum, anal canal Nerve to levator ani (branches of S4), inferior anal (rectal) nerve, coccygeal plexus Helps support pelvic viscera; resists increases in intra-abdo minal pressure Coccygeus (ischiococcygeus) Ischial spine Inferior end of sacrum and coccyx Branches of Forms S4 and S5 small part nerves of pelvic diaphragm that supports pelvic viscera; flexes coccyx Obturator internus Pelvic surface of ilium and ischium; obturator membrane Greater trochanter of femur Nerve to obturator internus (L5, S1, S2) Laterally rotates hip joint; assists in holding head of femur in acetabulum Piriformis Pelvic surface of 2nd–4th sacral segments; superior margin of greater sciatic notch and Anterior rami of S1 and S2 Laterally rotates hip joint; abducts hip joint; assists in holding head of femur in acetabulum sacrotuberou s ligament The lateral pelvic walls ● ● have a bony framework formed by the hip bones, including the obturator foramen (Fig. 6.2C); the obturator foramen is closed by the obturator membrane (Fig. 6.3). ● ● are covered and padded by the obturator internus muscles (Fig. 6.7A,B,D). Each obturator internus converges posteriorly from its origin within the lesser pelvis, exits through the lesser sciatic foramen, and turns sharply laterally to attach to the femur (Fig. 6.7D). The medial surfaces of these muscles are covered by obturator fascia, thickened centrally as a tendinous arch that provides attachment for the levator ani (pelvic diaphragm) (Fig. 6.7B,E). ● ● have the obturator nerves and vessels and other branches of the internal iliac vessels located on their medial aspects (medial to obturator internus muscles) The posterior pelvic wall ● ● consists of a bony wall and roof in the midline (formed by the sacrum and coccyx) and musculoligamentous posterolateral walls (formed by the sacro-iliac joints and their associated ligaments and piriformis muscles). Each piriformis muscle leaves the lesser pelvis through the greater sciatic foramen to attach to the femur (Fig. 6.7A). ● ● is the site of the nerves forming the sacral plexus; the piriformis muscles form a “muscular bed” for this nerve network (Fig. 6.7D,E). The pelvic floor is formed by the bowl- or funnel-shaped pelvic diaphragm, which consists of the levator ani and coccygeus muscles and the fascias (L. fasciae) covering the superior and inferior aspects of these muscles (Fig. 6.7A). The coccygeus muscles extend from the ischial spines to the pubic bones anteriorly, to the ischial spines posteriorly, and to a thickening in the obturator fascia (tendinous arch of levator ani) on each side (Fig. 6.7A,C,E). The levator ani consists of three parts, each named according to the attachment of its fibers (Fig. 6.7A,C,E and Table 6.3). The parts of the levator ani are as follows: ● ● The puborectalis, consisting of the thicker, narrower, medial part of the levator ani, which is continuous between the posterior aspects of the right and left pubic bones. It forms a U-shaped muscular sling (puborectal sling) that passes posterior to the anorectal junction. This part plays a major role in maintaining fecal continence. ● ● The pubococcygeus, the wider but thinner intermediate part of the levator ani, which arises from the posterior aspect of the body of the pubis and the anterior part of the tendinous arch and passes posteriorly in a nearly horizontal plane. The lateral fibers attach posteriorly to the coccyx, and the medial fibers merge with those of the contralateral side to form part of the anococcygeal body or ligament. ● ● The iliococcygeus, the posterolateral part of the levator ani, which arises from the posterior part of the tendinous arch and ischial spine; it is thin and often poorly developed and blends with the anococcygeal body posteriorly. The levator ani forms a dynamic floor for supporting the abdominopelvic viscera. Acting together, the parts of the levator ani raise the pelvic floor, following its descent when relaxed to allow defecation and urination, restoring its normal position. Further contraction occurs when the thoracic diaphragm and anterolateral abdominal wall muscles contract to compress the abdominal and pelvic contents. Therefore, it can resist the increased intra-abdominal pressure that would otherwise force the abdominopelvic contents (gas, solid and liquid wastes, and the viscera) through the pelvic outlet. This action occurs reflexively during forced expiration, coughing, sneezing, vomiting, and fixation of the trunk during strong movements of the upper limbs, as occurs when lifting a heavy object. The levator ani also has important functions in the voluntary control of urination, fecal continence (via the puborectalis), and support of the uterus. Pelvic Fascia The pelvic fascia is connective tissue that occupies the space between the membranous peritoneum and the muscular pelvic walls and floor not occupied by pelvic organs (Fig. 6.8). This “layer” is a continuation of the comparatively thin endo-abdominal fascia that lies between the muscular abdominal walls and the peritoneum superiorly. FIGURE 6.8. View OriginalDownload Slide (.ppt) Pelvic fascia: endopelvic fascia and fascial ligaments. E Based on DeLancey JO. Structural support of the urethra as it relates to stress urinary incontinence: the hammock hypothesis. Am J Obstet Gynecol. 1994;170:1713–1720. Membranous Pelvic Fascia: Parietal and Visceral The parietal pelvic fascia is a membranous layer of variable thickness that lines the internal (deep or pelvic) aspect of the muscles forming the walls and floor of the pelvis. The parietal pelvic fascia covers the pelvic surfaces of the obturator internus, piriformis, coccygeus, levator ani, and part of the urethral sphincter muscles (Fig. 6.8A–D). The name given to the fascia is derived from the muscle it encloses (e.g., obturator fascia). This layer is continuous superiorly with the transversalis and iliopsoas fascias. The visceral pelvic fascia includes the membranous fascia that directly ensheathes the pelvic organs, forming the adventitial layer of each. The membranous parietal and visceral layers become continuous where the organs penetrate the pelvic floor (Fig. 6.8A,C,E). Here, the parietal fascia thickens, forming the tendinous arch of pelvic fascia, a continuous bilateral band running from the pubis to the sacrum along the pelvic floor adjacent to the viscera. The most anterior part of this tendinous arch (puboprostatic ligament in males; pubovesical ligament in females) connects the prostate to the pubis in the male or the fundus (base) of the bladder to the pubis in the female. The most posterior part of the band runs as the sacrogenital ligaments from the sacrum around the side of the rectum to attach to the prostate in the male or the vagina in the female. Endopelvic Fascia: Loose and Condensed The abundant connective tissue remaining between and continuous with the parietal and visceral membranous layers is extraperitoneal or subperitoneal endopelvic fascia (Fig. 6.8A–D). Some of this fascia is extremely loose areolar (fatty) tissue, relatively devoid of all but minor lymphatics and nutrient vessels. The retropubic (or prevesical, extended posterolaterally as paravesical) and retrorectal (or presacral) spaces are potential spaces in the loose fatty tissue that accommodate the expansion of the urinary bladder and rectal ampulla as they fill (Fig. 6.8B,D). Other parts of the endopelvic fascia have a fibrous consistency, the ligamentous fascia. These parts are often described as “fascial condensations” or pelvic “ligaments.” The hypogastric sheath is a thick band of condensed pelvic fascia that gives passage to essentially all the vessels and nerves passing from the lateral wall of the pelvis to the pelvic viscera, along with the ureters and, in the male, the ductus deferens. As it extends medially from the lateral wall, the hypogastric sheath divides into three laminae (“leaflets” or “wings”) that pass to or between the pelvic organs, conveying neurovascular structures and providing support. The three laminae of the hypogastric sheath, from anterior to posterior, are ● ● The lateral ligament of the bladder, passing to the bladder, conveying the superior vesical arteries and veins ● ● The middle lamina in the male, forming the rectovesical septum between the posterior surface of the bladder and the prostate anteriorly and the rectum posteriorly (Fig. 6.8D). In the female, the middle lamina is substantial and passes medially to the uterine cervix and vagina as the transverse cervical (cardinal) ligament, also known clinically as the lateral cervical or Mackenrodt ligament (Fig. 6.8B,E). In its most superior portion, at the base of the broad ligament, the uterine artery runs transversely toward the cervix, whereas the ureters course immediately inferior to them as they pass on each side of the cervix toward the bladder. ● ● The most posterior lamina passes to the rectum, conveying the middle rectal artery and vein (Fig. 6.8B,D). The transverse cervical ligament, and the way in which the uterus normally “rests” on top of the bladder, provides the main passive support for the uterus. The bladder, in turn, rests on the pubic bones and the symphysis anteriorly and on the anterior wall of the vagina posteriorly (Fig. 6.8E). The vagina, in turn, is suspended between the tendinous arches of the pelvic fascia by the paracolpium (Fig. 6.8A,E). In addition to this passive support, the perineal muscles provide dynamic support for the uterus, bladder, and rectum by contracting during moments of increased intra-abdominal pressure. There are surgically important potential pelvirectal spaces in the loose extraperitoneal connective tissue superior to the pelvic diaphragm. The spaces are divided into anterior and posterior regions by the lateral rectal ligaments, which are the posterior laminae of the hypogastric sheaths. These ligaments connect the rectum to the parietal pelvic fascia at the S2–S4 levels (Fig. 6.8B,D). Pelvic Nerves Pelvic structures are innervated mainly by the sacral (S1–S4) and coccygeal spinal nerves and the pelvic part of the autonomic nervous system (Fig. 6.9). The piriformis and coccygeus muscles form a bed for the sacral and coccygeal nerve plexuses. The anterior rami of the S2 and S3 nerves emerge between the digitations of these muscles (Fig. 6.9C). The descending part of the anterior ramus of L4 nerve unites with the anterior ramus of the L5 nerve to form the thick, cord-like lumbosacral trunk. It passes inferiorly, anterior to the ala of the sacrum, to join the sacral plexus. FIGURE 6.9. View OriginalDownload Slide (.ppt) View OriginalDownload Slide (.ppt) Nerves of sacral and coccygeal plexus. A and B. Schematic overview of nerves. C. Dissection of nerve plexuses. CLINICAL BOX Injury to Pelvic Floor During childbirth, the pelvic floor supports the fetal head while the cervix of the uterus is dilating to permit delivery of the fetus. The perineum, levator ani, and pelvic fascia may be injured during childbirth. It is the pubococcygeus, the main intermediate part of the levator ani, that is usually torn (Fig. B6.1). This part of the muscle is important because it encircles and supports the urethra, vagina, and anal canal. Weakening of the levator ani and pelvic fascia resulting from stretching or tearing during childbirth may alter the position of the neck of the bladder and urethra. These changes may cause urinary stress incontinence characterized by dribbling of urine when intra-abdominal pressure is raised during coughing and lifting, for instance. FIGURE B6.1. View OriginalDownload Slide (.ppt) Obstetrical injury. Sacral Plexus The sacral plexus is located on the posterolateral wall of the lesser pelvis, where it is closely related to the anterior surface of the piriformis. The two main nerves formed by the sacral plexus are the sciatic and pudendal nerves. Most branches of the sacral plexus leave the pelvis through the greater sciatic foramen (Fig. 6.9). The sciatic nerve, the largest nerve in the body, is formed by the anterior rami of spinal nerves L4–S3 (Fig. 6.9 and Table 6.4). The anterior rami converge on the anterior surface of the piriformis. Most commonly, the sciatic nerve passes through the greater sciatic foramen inferior to the piriformis to enter the gluteal region. TABLE 6.4. Nerves of Sacral and Coccygeal Plexuses Nervea Segmental Origin (Anterior Rami) Distribution 1 Sciatic L4, L5, S1, S2, S3 Articular branches to hip joint and muscular branches to flexors of knee (hamstring muscles) and all muscles in leg and foot 2 Superior gluteal L4, L5, S1 Gluteus medius, gluteus minimus, and tensor fasciae latae muscles 3 Inferior gluteal L5, S1, S2 Gluteus maximus muscle 4 Nerve to piriformis S1, S2 Piriformis muscle 5 Nerve to quadratus femoris and inferior gemellus L4, L5, S1 Quadratus femoris and inferior gemellus muscles 6 Nerve to obturator internus and superior gemellus L5, S1, S2 Obturator internus and superior gemellus muscles 7 Pudendal S2, S3, S4 Structures in perineum: sensory to genitalia, muscular branches to perineal muscles, sphincter urethrae, and external anal sphincter 8 Nerves to levator ani S3, S4 and coccygeus Levator ani and coccygeus muscles 9 Posterior femoral cutaneous S2, S3 Cutaneous branches to buttocks and uppermost medial and posterior surfaces of thigh 10 Perforating cutaneous S2, S3 Cutaneous branches to medial part of buttocks 11 Pelvic splanchnic aNumbers S2, S3, S4 Pelvic viscera via inferior hypogastric and pelvic plexus refer to Figure 6.9. The pudendal nerve is the main nerve of the perineum and the chief sensory nerve of the external genitalia. It is derived from the anterior rami of spinal nerves S2–S4. It accompanies the internal pudendal artery and leaves the pelvis through the greater sciatic foramen between the piriformis and the coccygeus muscles. The pudendal nerve hooks around the ischial spine and sacrospinous ligament and enters the perineum through the lesser sciatic foramen. It supplies the skin and muscles of the perineum, including the terminal parts of the reproductive, urinary, and digestive tracts. The superior gluteal nerve arises from the anterior rami of spinal nerves L4–S1 and leaves the pelvis through the greater sciatic foramen with the superior gluteal vessels, superior to the piriformis. It supplies three muscles in the gluteal region: the gluteus medius and minimus and the tensor fasciae latae (see Chapter 7, Lower Limb). The inferior gluteal nerve arises from the anterior rami of spinal nerves L5–S2 and leaves the pelvis through the greater sciatic foramen with the inferior gluteal vessels, inferior to the piriformis and superficial to the sciatic nerve. It breaks up into several branches that supply the overlying gluteus maximus muscle (see Chapter 7). Coccygeal Plexus The coccygeal plexus is a small network of nerve fibers formed by the anterior rami of spinal nerves S4 and S5 and the coccygeal nerves (Fig. 6.9B). It lies on the pelvic surface of the coccygeus and supplies this muscle, part of the levator ani, and the sacrococcygeal joint. The anococcygeal nerves arising from this plexus pierce the sacrotuberous ligament and supply a small area of skin between the tip of the coccyx and the anus (Fig. 6.9C). Obturator Nerve Although it passes through the pelvis, the obturator nerve is not a “pelvic nerve” but is rather the primary nerve to the medial thigh. It arises from the lumbar plexus (anterior rami of spinal nerves L2–L4) in the abdomen (greater pelvis) and enters the lesser pelvis (Fig. 6.9C). It runs in the extraperitoneal fat along the lateral wall of the pelvis to the obturator canal, the opening in the obturator membrane, where it exits the pelvis and enters the medial thigh. CLINICAL BOX Injury to Pelvic Nerves During childbirth, the fetal head may compress the mother’s sacral plexus, producing pain in her lower limbs. The obturator nerve is vulnerable to injury during surgery (e.g., during removal of cancerous lymph nodes from the lateral pelvic wall). Injury to the obturator nerve may cause painful spasms of the adductor muscles of the thigh and sensory deficits in the medial thigh region (see Chapter 7, Upper Limb). Pelvic Autonomic Nerves Autonomic innervation of the pelvic cavity is via four routes: the sacral sympathetic trunks, hypogastric plexuses, pelvic splanchnic nerves, and peri-arterial plexuses. The sacral sympathetic trunks are the inferior continuations of the lumbar sympathetic trunks (Fig. 6.10). Each sacral trunk usually has four sympathetic ganglia. The sacral trunks descend on the pelvic surface of the sacrum just medial to the pelvic sacral foramina and commonly converge to form the small median ganglion impar anterior to the coccyx (Fig. 6.10). The sympathetic trunks descend posterior to the rectum in the extraperitoneal connective tissue and send communicating branches, gray rami communicantes, to each of the anterior rami of the sacral and coccygeal nerves. They also send branches to the median sacral artery and the inferior hypogastric plexus. The primary function of the sacral sympathetic trunks is to provide postsynaptic fibers to the sacral plexus for sympathetic innervation of the lower limb. FIGURE 6.10. View OriginalDownload Slide (.ppt) Autonomic nerves of pelvis. The hypogastric plexuses (superior and inferior) are networks of sympathetic and visceral afferent nerve fibers. The main part of the superior hypogastric plexus lies just inferior to the bifurcation of the aorta and descends into the pelvis. This plexus is the inferior prolongation of the intermesenteric plexus (see Chapter 5, Abdomen), which also receives the L3 and L4 splanchnic nerves. The superior hypogastric plexus enters the pelvis, dividing into left and right hypogastric nerves, which descend anterior to the sacrum. These nerves descend lateral to the rectum within the hypogastric sheaths and then spread as they merge with pelvic splanchnic nerves (parasympathetic) to form the right and left inferior hypogastric plexuses. Subplexuses of the inferior hypogastric plexuses, pelvic plexuses, in both sexes pass to the lateral surfaces of the rectum and to the inferolateral surfaces of the urinary bladder and in males to the prostate and seminal glands (vesicles) and in females to the cervix of the uterus and lateral parts of the fornix of the vagina. The pelvic splanchnic nerves contain presynaptic parasympathetic and visceral afferent fibers derived from the S2–S4 spinal cord segments and visceral afferent fibers from cell bodies in the spinal ganglia of the corresponding spinal nerves (Figs. 6.9B,C and 6.10 and Table 6.4). The pelvic splanchnic nerves merge with the hypogastric nerves to form the inferior hypogastric (and pelvic) plexuses. The hypogastric/pelvic system of plexuses, receiving sympathetic fibers via the lumbar splanchnic nerves and parasympathetic fibers via the pelvic splanchnic nerves, innervates the pelvic viscera. The sympathetic fibers produce vasomotion, inhibits peristaltic contraction of the rectum, and stimulates contraction of the genital organs during orgasm (producing ejaculation in the male). The parasympathetic fibers stimulate contraction of the rectum and bladder for defecation and urination, respectively. Parasympathetic fibers in the prostatic plexus penetrate the pelvic floor to supply the erectile bodies of the external genitalia, producing erection. The peri-arterial plexuses of the superior rectal, ovarian, and internal iliac arteries provide postsynaptic, sympathetic, vasomotor fibers to each of the arteries and its derivative branches. Visceral Afferent Innervation in Pelvis Visceral afferent fibers travel with the autonomic nerve fibers, although the sensory impulses are conducted centrally retrograde to the efferent impulses. In the pelvis, visceral afferent fibers conducting reflexive sensation (information that does not reach consciousness) travel with parasympathetic fibers to the spinal sensory ganglia of S2–S4. The route taken by visceral afferent fibers conducting pain sensation differs in relationship to an imaginary line, the pelvic pain line, that corresponds to the inferior limit of peritoneum (Fig. 6.6B,C), except in the case of the large intestine, where the pain line occurs midway along the length of the sigmoid colon. Visceral afferent fibers that transmit pain sensations from the viscera inferior to the pelvic pain line (structures that do not contact the peritoneum and the distal sigmoid colon and rectum) also travel with parasympathetic fibers to the spinal ganglia of S2–S4. However, visceral afferent fibers conducting pain from the viscera superior to the pelvic pain line (structures in contact with the peritoneum, except for the distal sigmoid colon and rectum) follow the sympathetic fibers retrogradely to inferior thoracic and superior lumbar spinal ganglia. Pelvic Arteries and Veins Four main arteries enter the lesser pelvis in females, three in males (Fig. 6.11A,D): ● ● The paired internal iliac arteries deliver the most blood to the lesser pelvis. They bifurcate into an anterior division and a posterior division, providing the visceral branches and parietal branches, respectively. ● ● The paired ovarian arteries (females) ● ● The median sacral artery ● ● The superior rectal artery FIGURE 6.11. View OriginalDownload Slide (.ppt) Arteries and veins of pelvis. The origin, course, and distribution of these arteries and their branches are summarized in Table 6.5. TABLE 6.5. Arteries of Lesser Pelvisa Artery Origin Course Distribution Internal iliac (2) Common iliac artery Passes over pelvic brim to reach pelvic cavity Main blood supply to pelvic organs, gluteal muscles, and perineum Anterior division of internal iliac artery Internal iliac artery Passes anteriorly and divides into visceral branches and obturator artery Pelvic viscera and muscles in medial compartment of thigh Umbilical Anterior division of internal iliac artery Short pelvic course; obliterates after origin of superior vesical artery Via superior vesical artery Runs antero-inferiorly on lateral pelvic wall Pelvic muscles, nutrient artery to ilium, and head of femur Obturator (4) Superior vesical artery Patent part of umbilical artery Passes to superior aspect of urinary bladder Superior aspect of urinary bladder; often ductus deferens in male Artery to ductus deferens Superior or inferior vesical artery Runs subperitoneally to ductus deferens Ductus deferens Inferior vesicalb Anterior division of internal iliac artery Passes subperitoneally to inferior aspect of male urinary bladder Urinary bladder and pelvic part of ureter, seminal gland, and prostate in males Descends in pelvis to rectum Seminal gland, prostate, and rectum Middle rectal (11) Internal pudendal (10) Leaves pelvis through greater sciatic foramen and enters perineum (ischio-anal fossa) by passing through lesser sciatic foramen Main artery to perineum, including muscles of anal canal and perineum; skin and urogenital triangle; erectile bodies Inferior glutealc (9) Leaves pelvis through greater sciatic foramen inferior to piriformis Piriformis, coccygeus, levator ani, and gluteal muscles Uterine Runs medially on levator ani; crosses ureter to reach base of broad ligament Pelvic part of ureter, uterus, ligament of uterus, uterine tube, and vagina Vagina and branches to inferior part of urinary bladder Vaginal Anterior division of internal iliac artery (uterine artery) At junction of body and cervix of uterus, it descends to vagina Gonadal (testicular and ovarian) Abdominal aorta Descends retroperitoneally; Testis and ovary, testicular artery passes into respectively deep inguinal ring; ovarian artery crosses brim of pelvis and runs medially in suspensory ligament to ovary. Posterior division of internal iliac artery Internal iliac artery Passes posteriorly and gives rise to parietal branches Pelvic wall and gluteal region Iliolumbar Ascends anterior to sacro-iliac joint and posterior to common iliac vessels and psoas major Iliacus, psoas major, quadratus lumborum muscles, and cauda equina in vertebral canal Lateral sacral (7) Runs on superficial aspect of piriformis Piriformis and vertebral canal Superior gluteal (8) Leaves pelvis through greater sciatic foramen, superior to piriformis Gluteal muscles and tensor fasciae latae aNumbers Posterior division of internal iliac artery in parentheses refer to Fig. 6.11A & D. bOften arises from uterine artery in females. cOften arises from posterior division of internal iliac artery. The pelvis is drained by the following: ● ● Mainly, the internal iliac veins and their tributaries ● ● Superior rectal veins (see portal venous system, Chapter 5, Abdomen) ● ● Median sacral vein ● ● Ovarian veins (females) ● ● Internal vertebral venous plexus (see Chapter 2, Back) Pelvic venous plexuses are formed by the interjoining of veins in the pelvis (Fig. 6.11B,C). The various plexuses (rectal, vesical, prostatic, uterine, and vaginal) unite and drain mainly into the internal iliac vein, but some drain through the superior rectal vein into the inferior mesenteric vein or through lateral sacral veins into the internal vertebral venous plexus. Lymph Nodes of Pelvis The lymph nodes draining pelvic organs are variable in number, size, and location. They are somewhat arbitrarily divided into four primary groups of nodes named for the blood vessels with which they are associated (Fig. 6.12): ● ● External iliac lymph nodes receive lymph mainly from the inguinal lymph nodes; however, they also receive lymph from pelvic viscera, especially the superior parts of the anterior pelvic organs. Whereas most of the lymphatic drainage from the pelvis tends to parallel routes of venous drainage, the lymphatic drainage to the external iliac nodes does not. These nodes drain into the common iliac nodes. ● ● Internal iliac lymph nodes receive drainage from the inferior pelvic viscera, deep perineum, and gluteal region and drain into the common iliac nodes. ● ● Sacral lymph nodes, in the concavity of the sacrum, receive lymph from postero-inferior pelvic viscera and drain either to internal or to common iliac nodes. ● ● Common iliac lymph nodes receive drainage from the three main groups listed above. These nodes begin a common route for drainage from the pelvis that passes next to the lumbar (caval/aortic) nodes. FIGURE 6.12. View OriginalDownload Slide (.ppt) Lymph nodes of pelvis. A smaller group of lymph nodes, pararectal nodes, drain primarily to the inferior mesenteric nodes. Both primary and minor groups of pelvic nodes are highly interconnected, so that many nodes can be removed without disturbing drainage. This also allows cancer to spread in virtually any direction to any pelvic or abdominal viscus. The drainage pattern is not sufficiently predictable to allow the progress of metastatic cancer from pelvic organs to be reliably staged in a manner comparable to that of breast cancer. Pelvic Viscera Listen The pelvic viscera include the caudal parts of the intestinal (rectum) and urinary tracts and the reproductive system (Figs. 6.13, 6.14, 6.15). Although the sigmoid colon and parts of the small bowel extend into the pelvic cavity, they are mobile from their abdominal attachments; therefore, they are abdominal rather than pelvic viscera. FIGURE 6.13. View OriginalDownload Slide (.ppt) Urinary organs. FIGURE 6.14. View OriginalDownload Slide (.ppt) Viscera in hemisected male pelvis. The urinary bladder is distended, as if full. FIGURE 6.15. View OriginalDownload Slide (.ppt) Viscera in hemisected female pelvis. Urinary Organs The pelvic urinary organs include the following (Fig. 6.13): ● ● Ureters, which carry urine from the kidneys ● ● Urinary bladder, which temporarily stores urine ● ● Urethra, which conducts urine from the urinary bladder to the exterior Ureters The ureters are retroperitoneal muscular tubes that connect the kidneys to the urinary bladder. Urine is transported down the ureters by peristaltic contractions. The ureters run inferiorly from the kidneys, passing over the pelvic brim at the bifurcation of the common iliac arteries (Figs. 6.14 and 6.15). The ureters then run postero-inferiorly on the lateral walls of the pelvis and anterior and parallel to the internal iliac arteries. Opposite the ischial spine, they curve anteromedially, superior to the levator ani, to enter the urinary bladder. The ureters pass inferomedially through the muscular wall of the urinary bladder. This oblique passage through the bladder wall forms a one-way “flap valve”; the internal pressure of the filling bladder causes the intramural passage to collapse. In males, the only structure that passes between the ureter and the peritoneum is the ductus deferens. The ureter lies posterolateral to the ductus deferens and enters the posterosuperior angle of the bladder (Fig. 6.14; see also Fig. 6.18). In females, the ureter passes medial to the origin of the uterine artery and continues to the level of the ischial spine, where it is crossed superiorly by the uterine artery (Fig. 6.15). The ureter then passes close to the lateral fornix of the vagina and enters the posterosuperior angle of the bladder. Vasculature of Ureters Branches of the common and internal iliac arteries supply the pelvic part of the ureters (Fig. 6.16). The most constant arteries supplying this part of the ureters in females are branches of the uterine arteries. The sources of similar branches in males are the inferior vesical arteries. Veins from the ureters accompany the arteries and have corresponding names. As they course inferiorly, lymph drains sequentially into the lumbar (caval/aortic), common iliac, external iliac, and then internal iliac lymph nodes (Fig. 6.12). FIGURE 6.16. View OriginalDownload Slide (.ppt) Blood supply of ureters. Innervation of Ureters The nerves to the ureters derive from adjacent autonomic plexuses (renal, aortic, superior and inferior hypogastric). The ureters are superior to the pelvic pain line (see Figs. 6.6 and 6.24); therefore, afferent (pain) fibers from the ureters follow sympathetic fibers retrogradely to reach the spinal ganglia and spinal cord segments T11–L1 or L2 (Fig. 6.17). FIGURE 6.17. View OriginalDownload Slide (.ppt) Innervation of ureters. CLINICAL BOX Ureteric Calculi Ureteric calculi (stones) may cause complete or intermittent obstruction of urinary flow. The obstructing stone may lodge anywhere along the ureter; however, it lodges most often where the ureters are relatively constricted: (1) at the junction of the ureters and renal pelvis, (2) where they cross the external iliac artery and the pelvic brim, and (3) where they pass through the wall of the bladder. The severity of the pain associated with calculi can be extremely intense; it depends on the location, type, size, and texture of the calculus. Ureteric calculi can be removed by open surgery, endoscopy, or lithotripsy (shock waves to break the stones into small fragments that can be passed in the urine). Urinary Bladder The urinary bladder, a hollow viscus (organ) with strong muscular walls, is in the lesser pelvis when empty, its anterior portion directly superior to the pubic bones. It is separated from these bones by the potential retropubic space and lies inferior to the peritoneum, where it rests on the pelvic floor (Figs. 6.18, 6.19, 6.20). The bladder is relatively free within the extraperitoneal subcutaneous fatty tissue, except for its neck, which is held firmly by the lateral ligaments of the bladder and the tendinous arch of pelvic fascia, especially the puboprostatic ligament in males and the pubovesical ligament in females. As the bladder fills, it ascends superiorly into the extraperitoneal fatty tissue of the anterior abdominal wall and enters the greater pelvis. A full bladder may ascend to the level of the umbilicus. FIGURE 6.18. View OriginalDownload Slide (.ppt) Male pelvis demonstrating bed of bladder and position of empty and full bladder. FIGURE 6.19. View OriginalDownload Slide (.ppt) Surfaces of urinary bladder. FIGURE 6.20. View OriginalDownload Slide (.ppt) Coronal sections of male (A) and female (B) pelves in plane of pelvic portion of urethra. B Modified from Detton AJ. Grant’s Dissector. 16th ed. 2017; Fig. 5.37. When empty, the bladder is somewhat tetrahedral and externally has an apex, body, fundus, and neck. The four surfaces are a superior surface, two inferolateral surfaces, and a posterior surface (Fig. 6.19). The apex of the bladder (anterior end) points toward the superior edge of the pubic symphysis. The fundus of the bladder (base) is opposite the apex, formed by the somewhat convex posterior wall. The body of the bladder is the part between the apex and the fundus. In females, the fundus is closely related to the anterior wall of the vagina; in males, it is related to the rectum. The neck of the bladder is where the fundus and inferolateral surfaces converge inferiorly. The bladder bed is formed on each side by the pubic bones and the fascia covering the obturator internus and levator ani muscles and posteriorly by the rectum or vagina (Figs. 6.18 and 6.20). The bladder is enveloped by loose connective tissue, the vesical fascia. Only the superior surface is covered by peritoneum. The walls of the bladder are composed chiefly of the detrusor muscle (Fig. 6.20A). Toward the neck of the male bladder, its muscle fibers form the involuntary internal urethral sphincter (Fig. 6.18). This sphincter contracts during ejaculation to prevent retrograde ejaculation of semen into the bladder. Some fibers run radially and assist in opening the internal urethral orifice. In males, the muscle fibers in the neck of the bladder are continuous with the fibromuscular tissue of the prostate, whereas in females, these fibers are continuous with muscle fibers in the wall of the urethra. The ureteric orifices and the internal urethral orifice are at the angles of the trigone of the bladder (Fig. 6.20). The ureteric orifices are encircled by loops of detrusor musculature that tighten when the bladder contracts to assist in preventing reflux of urine into the ureters. The uvula of the bladder is a slight elevation of the trigone in the internal urethral orifice. Vasculature of Bladder The main arteries supplying the bladder are branches of the internal iliac arteries (Fig. 6.11A,D and Table 6.5). The superior vesical arteries supply the anterosuperior parts of the bladder. In males, the fundus and neck of the bladder are supplied by the inferior vesical arteries (Fig. 6.21). In females, the inferior vesical arteries are replaced by the vaginal arteries, which send small branches to the postero-inferior parts of the bladder. The obturator and inferior gluteal arteries also supply small branches to the bladder. FIGURE 6.21. View OriginalDownload Slide (.ppt) Male pelvic genitourinary organs. On the left side, the ampulla of ductus deferens, seminal gland, and prostate have been sectioned to the midline in a coronal plane, and the arterial supply to these structures and the bladder is demonstrated. The names of the veins draining the bladder correspond to the arteries and are tributaries of the internal iliac veins. In males, the vesical venous plexus is continuous with the prostatic venous plexus (Fig. 6.21; see also Fig. 6.60C), and the combined plexus envelops the fundus of the bladder and prostate, the seminal glands, the ductus deferentes (plural of ductus deferens), and the inferior ends of the ureters. The prostatic venous plexus also receives blood from the deep dorsal vein of the penis. The vesical venous plexus mainly drains through the inferior vesical veins into the internal iliac veins (see Fig. 6.11B,C); however, it may drain through the sacral veins into the internal vertebral venous plexuses (see Chapter 2, Back). In females, the vesical venous plexus envelops the pelvic part of the urethra, and the neck of the bladder receives blood from the dorsal vein of the clitoris and communicates with the vaginal or uterovaginal venous plexus (Fig. 6.11B). In both sexes, lymphatic vessels leave the superior surface of the bladder and pass to the external iliac lymph nodes (Figs. 6.22 and 6.23 and Tables 6.6 and 6.7), whereas those from the fundus pass to the internal iliac lymph nodes. Some vessels from the neck of the bladder drain into the sacral or common iliac lymph nodes. FIGURE 6.22. View OriginalDownload Slide (.ppt) Lymphatic drainage of female pelvis and perineum. FIGURE 6.23. View OriginalDownload Slide (.ppt) Lymphatic drainage of male pelvis and perineum. TABLE 6.6. Lymphatic Drainage of Female Pelvis and Perineum Lymph Node Group Typically Drains Lumbar (along ovarian vessels) Gonads and associated structures, common iliac nodes (ovary, uterine tube except isthmus and intrauterine parts, fundus of uterus) Inferior mesenteric Superiormost rectum, sigmoid colon, descending colon, pararectal nodes Internal iliac Inferior pelvic structures, deep perineal structures, sacral nodes (base of bladder, inferior pelvic ureter, anal canal above pectinate line, inferior rectum, middle and upper vagina, cervix, body of uterus) External iliac Anterosuperior pelvic structures, deep inguinal nodes (superior bladder, superior pelvic ureter, upper vagina, cervix, lower body of uterus) Superficial inguinal Lower limb; superficial drainage of inferolateral quadrant of trunk, including anterior abdominal wall inferior to umbilicus, gluteal region, superficial perineal structures (superolateral uterus near attachment of round ligament, skin of perineum including vulva, ostium of vagina inferior to hymen, prepuce of clitoris, peri-anal skin, anal canal inferior to pectinate line) Deep inguinal Glans clitoris, superficial inguinal nodes Sacral Postero-inferior pelvic structures, inferior rectum, inferior vagina Pararectal Superior rectum TABLE 6.7. Lymphatic Drainage of Male Pelvis and Perineum Lymph Node Group Typically Drains Lumbar (near testicular vessels) Urethra, testis, epididymis Inferior mesenteric Superiormost rectum, sigmoid colon, descending colon, pararectal nodes Internal iliac External and internal iliac lymph nodes External iliac Inferior pelvic structures, deep perineal structures, sacral nodes (prostatic urethra, prostate, base of bladder, inferior pelvic ureter, inferior seminal glands, cavernous bodies, anal canal above pectinate line, inferior rectum) Superficial inguinal Lower limb; superficial drainage of inferolateral quadrant of trunk, including anterior abdominal wall inferior to umbilicus, gluteal region, superficial perineal structures (skin of perineum, including skin and prepuce of penis, scrotum, peri-anal skin, anal canal inferior to pectinate line) Deep inguinal Glans penis, superficial inguinal nodes, distal spongy urethra Sacral Postero-inferior pelvic structures, inferior rectum Pararectal Superior rectum CLINICAL BOX Suprapubic Cystostomy As the bladder fills, it extends superiorly in the extraperitoneal fatty tissue of the anterior abdominal wall (Fig. 6.18). The bladder then lies adjacent to this wall without the intervention of peritoneum. Consequently, the distended bladder may be punctured (suprapubic cystostomy) or approached surgically for the introduction of indwelling catheters or instruments without traversing the peritoneum and entering the peritoneal cavity. Rupture of Bladder Because of the superior position of a distended bladder, it may be ruptured by injuries to the inferior part of the anterior abdominal wall or by fractures of the pelvis. The rupture of the superior part of the bladder frequently tears the peritoneum, resulting in passage of urine into the peritoneal cavity. Posterior rupture of the bladder usually results in passage of urine subperitoneally into the perineum. Cystoscopy The interior of the bladder and its three orifices can be examined with a cystoscope, a lighted tubular endoscope that is inserted through the urethra into the bladder. The cystoscope consists of a light; an observing lens; and various attachments for grasping, removing, cutting, and cauterizing (Fig. B6.2). FIGURE B6.2. View OriginalDownload Slide (.ppt) Cystoscopy. Hartwig W. Fundamental Anatomy. 2008:176. Innervation of Bladder Sympathetic fibers to the bladder are conveyed from the T11–L2 or L3 spinal cord levels to the vesical (pelvic) plexuses, primarily through the hypogastric/pelvic plexuses and nerves, whereas parasympathetic fibers from the sacral spinal cord levels are conveyed by the pelvic splanchnic nerves and the inferior hypogastric plexuses (Fig. 6.24). Parasympathetic fibers are motor to the detrusor muscle in the bladder wall and inhibitory to the internal sphincter of males. Hence, when the visceral afferent fibers are stimulated by stretching, the detrusor contracts, the internal sphincter relaxes in males, and urine flows into the urethra. Toilet training suppresses this reflex until it is convenient to void. The sympathetic innervation that stimulates ejaculation simultaneously causes contraction of the internal urethral sphincter, preventing reflux of semen into the bladder. FIGURE 6.24. View OriginalDownload Slide (.ppt) Innervation of urinary bladder and urethra. Sensory fibers from the bladder are visceral; reflex afferents and pain afferents (e.g., from overdistention) from the inferior part of the bladder follow the course of the parasympathetic fibers. The superior surface of the bladder is covered with peritoneum and is, therefore, superior to the pain line; thus, pain fibers from the superior part of the bladder follow the sympathetic fibers retrogradely. Female Urethra The short female urethra passes antero-inferiorly from the internal urethral orifice of the urinary bladder, posterior, and then inferior to the pubic symphysis to the external urethral orifice in the vestibule of the vagina (Fig. 6.20B). The urethra lies anterior to the vagina; its axis is parallel with the vagina. The urethra passes with the vagina through the pelvic diaphragm, external urethral sphincter, and perineal membrane. Urethral glands are