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Essential clinical anatomy part 02, Notas de estudo de Informática

ESSENTIAL CLINICAL ANATOMY PART 02

Tipologia: Notas de estudo

2010

Compartilhado em 15/09/2010

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Baixe Essential clinical anatomy part 02 e outras Notas de estudo em PDF para Informática, somente na Docsity! P.205 Chapter 3 Pelvis and Perineum FIGURE 3.1. 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. Light green, greater pelvis; dark green, lesser pelvis. 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. 3.1). 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. PELVIS The superior boundary of the pelvic cavity is the pelvic inlet , the superior pelvic aperture (Figs. 3.1 and 3.2). The pelvis is limited inferiorly by the pelvic out let , the inferior pelvic aperture, which is bounded anteriorly by the pubic symphysis (L. symphysis pubis) and posteriorly by the coccyx. 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 out let (inferior pelvic aperture) is bounded by the: P.206 Inferior margin of the pubic symphysis anteriorly. Inferior rami of the pubis and ischial tuberosities anterolaterally. Sacrotuberous ligaments posterolaterally (Fig. 3.3B) Tip of the coccyx posteriorly Pelvic Girdle The pelvic girdle is a basin-shaped ring of bones that connects the vertebral column to the two femurs in the thighs. The main functions of the strong pelvic girdle are to transfer the weight of the upper body from the axial to the lower appendicular skeleton for standing and walking, and to withstand compression and other forces resulting from its support of body weight. The bony pelvis is formed by three bones (Fig. 3.2; Table 3.1): 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. 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. 3.2). 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. P.208 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. 3.3B). 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 3.2, Fig. 3.1B). FIGURE 3.4. Comparison of male and female. TABLE 3.1 COMPARISON OF MALE AND FEMALE BONY PELVES Bony Pelvis Male (々) Female (仝) General structure Thick and heavy Thin and light Greater pelvis (pelvis major) Deep Shallow P.209 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 (^) Narrow (<70°) Wide (>80°) Obturator foramen Round Oval Acetabulum Large Small Sexual Differences in Bony Pelves The male and female bony pelves differ in several respects (Fig. 3.4 and Table 3.1). 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 (and the pelvic brim) 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. The ischial spines face each other and the interspinous distance between them is the narrowest part of the pelvic canal (the passageway traversing the pelvic inlet, lesser pelvis, and pelvic outlet through which a baby's head must pass at birth). 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. 3.2A). The lumbosacral and sacrococcygeal joints are directly related to the pelvic girdle. Strong ligaments support and strengthen these joints (Fig. 3.3). 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. 3.2C and 3.5). 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. 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 P.210 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 Blue 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. 3.3). 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. 3.5C). 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. 3.3 and 3.5D). The fibrocartilaginous interpubic disc is generally wider in women than in men. The ligaments joining the pubic bones are thickened superi they orly 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 and S1 vertebrae articulate anteriorly at the anterior intervertebral joint , formed by the L5/S1 intervertebral (IV) disc between their bodies posteriorly and (Fig. 3.1A) at two zygapophysial joints (facet joints) between the articular processes of these vertebrae (Fig. 3.3B). The facets on the S1 vertebra face posteromedially, interlocking with the anterolaterally facing inferior articular facets of the L5 vertebra, preventing L5 from sliding anteriorly. I liolumbar ligaments unite the transverse processes of L5 to the ilia. P.212 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, 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, 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. FIGURE 3.6. Pelvic peritoneum. TABLE 3.2 PERITONEAL REFLECTIONS IN PELVIS P.213 Female (Parts A & B)a Male (Part C)a 1 Descends anterior abdominal wall (loose attachment allows insertion of bladder as it fills) 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 4 Reflects from bladder body of uterus, forming vesico-uterine pouch 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 6 Reflects from vagina onto rectum, forming recto-uterine pouchb (pouch of Douglas) 7 Recto-uterine 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 9 Engulfs sigmoid colon beginning at rectosigmoid junction 1 Descends anterior abdominal wall (loose attachment allows insertion of bladder as it fills) 2 Reflects onto superior surface of bladder, creating supravesical fossa 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 Descends posterior surface of bladder as much as 2 cm 5 Laterally, forms fold over ureters (ureteric fold), ductus deferentes, and superior ends of seminal glands 6 Reflects from bladder and seminal glands onto rectum, forming rectovesical pouchb 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 9 Engulfs sigmoid colon beginning at rectosigmoid junction a Numbers refer to Figure 3.6. b Low point of peritoneal cavity in erect position. FIGURE 3.7. A. and B. Muscles of pelvic w alls and floor. C-E. Muscles of pelvic w alls and floor TABLE 3.3 MUSCLES OF PELVIC WALLS AND FLOOR Muscle Proximal Attachment Distal Attachment Innervat ion Main Action Levator ani (pubococcygeus and iliococcygeus) Body of pubis, tendinous arch of levator ani, ischial spine Perineal body, coccyx, anococcygeal ligament, walls of prostate or vagina, Nerve to levator ani (branches of S4), inferior anal (rectal) nerve, coccygeal Helps support pelvic viscera; resists increases in intra- P.216 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. 3.8A-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. 3.8A,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 (puboprostat ic 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 Usually, the abundant connective tissue remaining between the parietal and visceral membranous layers is considered part of the visceral fascia, but various authors label parts of it as parietal. It is probably more realistic to consider this remaining fascia simply as extraperitoneal or subperitoneal endopelvic fascia (Fig. 3.8A-D), which is continuous with both the parietal and the visceral membranous fascias. 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. 3.8B,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. 3.8D). In the female, the middle lamina is substantial and passes medially to the uterine cervix and vagina as the cardinal ligament (transverse cervical), also known clinically as the lateral cervical or Mackenrodt ligament (Fig. 3.8B,E). In its most superior portion, at the base of the broad ligament, the uterine artery runs transversely toward the cervix while 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. 3.8B,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 uniting them anteriorly, and on the anterior wall of the vagina posteriorly (Fig. 3.8E). The vagina, in turn, is suspended between the tendinous arches of the pelvic fascia by the paracolpium (Fig. 3.8A,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. P.217 FIGURE 3.8. Pelvic fascia: endopelvic fascia and fascial ligaments. 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 (rectal stalks), 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. 3.8B,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. The piriformis and coccygeus muscles form a bed for the sacral and coccygeal nerve plexuses (Fig. 3.9C,D). The anterior rami of the S2 and S3 nerves emerge between the digitations of these muscles. 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 t runk. It passes inferiorly, anterior to the ala of the sacrum to join the sacral plexus. 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. B3.1). 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 B3.1. 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 of the sacral plexus are the sciatic and pudendal. Most branches of the sacral plexus leave the pelvis through the greater sciatic foramen (Fig. 3.9A). The sciat ic nerve, the largest nerve in the body, is formed by the anterior rami of spinal nerves L4-S3 (Fig. 3.9; Table 3.4). 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 (buttock) region. 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. The superior gluteal nerve arises from the anterior rami of spinal nerves L4-S1 and leaves the pelvis through the greater sciatic P.219 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 5). FIGURE 3.9. (continued) PELVIC AUTONOMIC NERVES Autonomic innervation of the pelvic cavity is via four routes: the sacral sympathetic trunks, periarterial plexuses, hypogastric plexuses, and pelvic splanchnic nerves. The sacral sympathet ic t runks are the inferior continuations of the lumbar sympathetic trunks (Fig. 3.9A,C,D). 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. 3.10). 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. The periarteria l plexuses of the superior rectal, ovarian, and internal iliac arteries provide postsynaptic, sympathetic, vasomotor fibers to each of the arteries and its derivative branches. 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 2), which also receives the L3 and L4 splanchnic nerves. The superior hypogastric plexus enter the pelvis, dividing into left and right hypogastric nerves, which descend anterior to the P.220 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. FIGURE 3.10. Autonomic nerves of pelvis. 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. 3.9B and 3.10; Table 3.4). 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 sympathet ic component produces vasomotion, inhibits peristaltic contraction of the rectum, and stimulates contraction of the genital organs during orgasm (producing ejaculation in the male). The parasympathet ic 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. 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. 3.6B, C), except in the case of the large intenstine, 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 fiber 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. P.221 Pelvic Arteries and Veins Four main arteries enter the lesser pelvis in females, three in males: The paired internal iliac arteries deliver the most blood to the lesser pelvis (Fig. 3.11A,D). They bifurcate into an anterior division and a posterior division, providing the visceral branches and parietal branches, respectively. The paired ovarian arteries. The median sacral artery. The superior rectal artery. Inferior gluteal 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 Vaginal Uterine artery At junction of body and cervix of uterus, it descends to vagina Vagina and branches to inferior part of urinary bladder Gonadal (testicular and ovarian) Abdominal aorta Descends retroperitoneally; testicular artery passes into deep inguinal ring; ovarian artery crosses brim of pelvis and runs medially in suspensory ligament to ovary Testis and ovary, respectively Posterior division of internal iliac artery Internal iliac artery Passes posteriorly and gives rise to parietal branches Pelvic wall and gluteal region Iliolumbar Posterior division of internal iliac artery 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 (superior and inferior) Run on superficial aspect of piriformis Piriformis and vertebral canal Superior gluteal Leaves pelvis through greater sciatic foramen, superior to piriformis Gluteal muscles and tensor fasciae latae a Often arises from posterior division of internal iliac artery P.223 The origin, course, and distribution of these arteries and their branches are summarized in Table 3.5. The pelvis is drained by the following: Mainly, the internal iliac veins and their tributaries. Superior rectal veins (see portal venous system, Chapter 2). Median sacral vein. Gonadal veins. Internal vertebral venous plexus (see Chapter 4). Pelvic venous plexuses are formed by the interjoining of veins in the pelvis (Fig. 3.11B,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. 3.12): 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 posteroinferior 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. Additional minor groups of nodes (e.g., the pararectal nodes ) occupy the connective tissue along the branches of the internal iliac vessels. 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. FIGURE 3.12. Lymph nodes of pelvis. PELVIC VISCERA The pelvic viscera include the inferior part of the intestinal tract (rectum), the urinary bladder, and parts of the ureters and reproductive system (Figs. 3.13, 3.14 and 3.15). Although the sigmoid colon and parts of the small bowel extend into the pelvic cavity, they are mobile at their abdominal attachments; therefore, they are abdominal rather than pelvic viscera. Urinary Organs The pelvic urinary organs are the (Fig. 3.13): 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 P.225 FIGURE 3.15. Female pelvis. C, cervix of uterus; O, ovary; PS, pubic symphysis; SN, sciatic nerve; UT, uterine tube. Vasculature of Ureters. Branches of the common and internal iliac arteries supply the pelvic part of the ureters (Fig. 3.16). 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. Lymph drains into the lumbar (caval/aortic), common iliac, external iliac, and internal iliac lymph nodes (Fig. 3.12). 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 (Figs. 3.6 and 3.24); 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. 3.17). FIGURE 3.16. Arteria l supply of ureter. F = female, M = male. Ureteric Calculi Ureteric calculi (stones) may cause complete or intermittent obstruction of urinary flow. The obstruction may occur anywhere along the ureter; however, it occurs 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 are used to break the stones into small fragments that can be passed in the urine). P.226 FIGURE 3.17. Innervat ion of ureter. URINARY BLADDER The urinary bladder, a hollow viscus with strong muscular walls, is in the lesser pelvis when empty, posterior and slightly superior to the pubic bones. It is separated from these bones by the retropubic space and lies inferior to the peritoneum, where it rests on the pelvic floor (Figs. 3.18, 3.19 and 3.20). The bladder is relatively free within the extraperitoneal subcutaneous fatty P.228 FIGURE 3.20. Coronal sect ions of male (A) and female (B) pelves in plane of pelvic port ion of urethra. Vasculature of Bladder. The main arteries supplying the bladder are branches of the internal iliac arteries (Fig. 3.11A,D; Table 3.5). 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. 3.21). In females, the inferior vesical arteries are replaced by the vaginal arteries, which send small branches to the posteroinferior parts of the bladder. The obturator and inferior gluteal arteries also supply small branches to the bladder. 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. 3.21), 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 (Fig. 3.11B,C); however, it may drain through the sacral veins into the internal vertebral venous plexuses (see Chapter 4). 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. 3.11B). In both sexes, lymphat ic vessels leave the superior surface of the bladder and pass to the external iliac lymph nodes (Figs. 3.22 and 3.23; Tables 3.6 and 3.7), 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 3.21. 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. 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 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. 3.24). 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 bladder contracts, the internal sphincter relaxes in males, and urine flows into the urethra. Adults suppress this reflex until it is convenient to void. The sympathetic innervation that stimulates ejaculation simultaneously causes contraction of the internal urethral sphincter, to prevent reflux of semen into the bladder. 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. Suprapubic Cystotomy As the bladder fills, it extends superiorly in the extraperitoneal fatty tissue of the anterior abdominal wall (Fig. 3.18). 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 (extravasation) of urine into the peritoneal cavity. Posterior rupture of the P.229 bladder usually results in passage of urine subperitoneally into the perineum. FIGURE 3.22. Lymphatic drainage of female pelvis and perineum. TABLE 3.6 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 Lower limb; superficial drainage of inferolateral quadrant of trunk, P.231 Deep inguinal Glans of penis, superficial inguinal nodes, distal spongy urethra Sacral Posteroinferior pelvic structures, inferior rectum Pararectal Superior rectum FEMALE URETHRA The short female urethra passes anteroinferiorly 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. 3.20B). 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 present, particularly in its superior part; the paraurethral glands are homologs to the prostate. These glands have a common paraurethral duct, which opens (one on each side) near the external urethral orifice. The inferior half of the urethra is in the perineum and is discussed in that section. Vasculature of Female Urethra. Blood is supplied by the internal pudendal and vaginal arteries (Fig. 3.11A; Table 3.5). The veins follow the arteries and have similar names. Most lymphatic vessels from the urethra pass to the sacral and internal iliac lymph nodes (Fig. 3.22; Table 3.6). A few vessels drain into the inguinal lymph nodes. Innervation of Female Urethra. The nerves to the urethra arise from the vesical (nerve) plexus and the pudendal nerve (Fig. 3.24). The pattern is similar to that in the male, given the absence of a prostatic plexus and an internal urethral sphincter. Visceral afferents from most of the urethra run in the pelvic splanchnic nerves, but the termination receives somatic afferents from the pudendal nerve. P.232 FIGURE 3.24. Autonomic innervat ion of urinary bladder and urethra. MALE URETHRA The male urethra is a muscular tube that conveys urine from the internal urethral orifice of the urinary bladder to the exterior through the external urethral orifice at the tip of the glans penis (Fig. 3.24). The urethra also provides an exit for semen (sperm and glandular secretions). For descriptive purposes, the urethra is divided into four parts: intramural part of the urethra (preprostatic urethra), prostatic urethra, intermediate (membranous) part of the urethra, and spongy (penile) part of the urethra (Figs. 3.20A and 3.25; Table 3.8). The intramural part of the male urethra is surrounded by an internal urethral sphincter composed of sympathetically innervated smooth muscle (Fig. 3.26). This sphincter prevents semen from entering the bladder during ejaculation (retrograde ejaculation). The prostate surrounds the prostatic urethra. The intermediate part of the male urethra is surrounded by the external urethral sphincter, composed of somatically innervated voluntary muscle. The tonic and phasic contraction of this muscle primarily controls urinary continence, but several other muscles may also contribute by compressing the urethra. Stimulation of both sphincters must be inhibited to enable urination. FIGURE 3.25. Parts of male urethra. TABLE 3.8 PARTS OF MALE URETHRA Part Length (cm) Locat ion/Disposit ion Features Intramural (preprostatic) part 0.5-1.5 Extends almost vertically through neck of bladder Surrounded by internal urethral sphincter; diameter and length vary, depending on whether bladder is filling or emptying Prostatic urethra 3.0-4.0 Descends through anterior prostate, forming gentle, anteriorly concave curve; is bounded anteriorly by vertical, trough-like part (rhabdosphincter) of Widest and most dilatable part; features urethral crest with seminal colliculus, flanked by prostatic sinuses into which the prostatic ducts open; ejaculatory ducts open onto colliculus; P.234 superior part, and the internal iliac lymph nodes from the inferior part (Table 3.7). EJACULATORY DUCTS Each ejaculatory duct is a slender tube that arises by the union of the duct of a seminal gland with the ductus deferens (Figs. 3.21 and 3.25). The ejaculatory ducts arise near the neck of the bladder and run close together as they pass anteroinferiorly through the posterior part of the prostate. The ducts converge to open by slit-like apertures on, or just within, the opening of the prostatic utricle (Fig. 3.28). Prostatic secretions join the seminal fluid in the prostatic urethra after the termination of the ejaculatory ducts. Vasculature of Ejaculatory Ducts. The arteries to the ductus deferentes, usually branches of the superior (but frequently inferior) vesical arteries, supply the ejaculatory ducts (Table 3.5). The veins join the prostatic and vesical venous plexuses. The lymphatic vessels drain into the external iliac lymph nodes (Table 3.7). PROSTATE The walnut-size prostate surrounds the prostatic urethra (Figs. 3.25 and 3.27). The glandular part makes up approximately two thirds of the prostate; the other third is fibromuscular. The structure has a dense fibrous capsule of the prostate that incorporates the prostatic plexuses of nerves and veins. This is surrounded by the visceral layer of the pelvic fascia, forming a fibrous prostatic sheath that is thin anteriorly, continuous anterolaterally with the puboprostatic ligaments, and dense posteriorly, continuous with the rectovesical septum. The prostate has (Fig. 3.27B): A base (superior aspect) that is closely related to the neck of the bladder. An apex (inferior aspect) that is in contact with fascia on the superior aspect of the urethral sphincter and deep perineal muscles. A muscular anterior surface that features mostly transversely oriented muscle fibers forming a vertical trough-like hemisphincter (rhabdosphincter), which is part the urethral sphincter, separated from the pubic symphysis by retroperitoneal fat in the retropubic space (Fig. 3.18). A posterior surface that is related to the ampulla of the rectum. Inferolateral surfaces that are related to the levator ani. P.235 FIGURE 3.27. Lobules and zones of prostate demonstrated by anatomical sect ion and ultrasonographic imaging. Although not clearly distinct anatomically, the following lobes and lobules of the prostate are described (Fig. 3.27A): The isthmus of the prostate (anterior muscular zone; historically, the anterior lobe) lies anterior to the urethra. It is primarily muscular and represents the superior continuation of the urethral sphincter muscle. Right and left lobes (peripheral zones), each divided in turn into four indistinct lobules in two concentric bands, defined by their relationship to the urethra and ejaculatory ducts: 1. A superfical inferoposterior lobule, posterior to the urethra and inferior to the ejaculatory ducts, is readily palpable by digital rectal examination. 2. A superficial inferolateral lobule, lateral to the urethra, forms the major part of the prostate. 3. A superomedial lobule surrounds the ejaculatory duct, deep to the inferoposterior lobule. 4. An anteromedial lobule, deep to the inferolateral lobule, is directly lateral to the proximal prostatic urethra. An embryonic middle (median) lobe gives rise to superomedial and anteromedial lobules. This region tends to undergo hormone- induced hypertrophy in advanced age, forming a middle lobule (central zone) believed to be partially responsible for the formation of the uvula that may project into the internal urethral orifice (Fig. 3.28). Urologists and sonographers usually divide the prostate into peripheral and central (internal) zones (Fig. 3.27C,D). The prostat ic ducts (20-30) open chiefly into the prostat ic sinuses that lie on either side of the seminal colliculus on the posterior wall of the prostatic urethra (Fig. 3.28). Prostatic fluid provides about 20% of the volume of semen (a mixture of secretions). Vasculature of Prostate. The prostatic arteries are mainly branches of the internal iliac artery (Table 3.5), especially the inferior vesical arteries but also the internal pudendal and middle rectal arteries. The veins join to form the prostat ic venous plexus around the sides and base of the prostate (Figs. 3.21 and 3.27B). This plexus, between the fibrous capsule of the prostate and the prostatic sheath, drains into the internal iliac veins. The plexus is continuous superiorly with the vesical venous plexus and communicates posteriorly with the internal vertebral venous plexus (see Chapter 4). The lymphatic vessels drain chiefly into the internal iliac nodes, but some pass to the sacral lymph nodes (Table 3.7). Prostat ic Enlargement, Prostat ic Cancer, and Prostotectomy The prostate is of medical interest because benign enlargement or benign hypertrophy of the prostate (BHP) is common after middle age. An enlarged prostate projects into the urinary bladder and impedes urination by distorting the prostatic urethra. The middle lobule usually enlarges the most and obstructs the internal urethral orifice. Prostatic cancer is common in men older than 55 years. In most cases, the cancer develops in the posterolateral region. This may be palpated during a digital rectal examination (Fig. B3.3). A malignant prostate feels hard and often irregular. In advanced stages, cancer cells metastasize (spread) to the iliac and sacral lymph nodes and later to distant nodes and bone. The prostatic plexus, closely associated with the prostatic sheath, gives passage to parasympathetic fibers, which give rise to the cavernous nerves that convey the fibers that cause penile erection. A major concern regarding prostatectomy is that impotency may be a consequence. All or part of the prostate, or just the hypertrophied part, is removed (transurethral resection of the prostate [TURP]). FIGURE B3.3. P.237 FIGURE 3.30. Vagina. VAGINA The vagina, a mostly subperitoneal musculomembranous tube, extends from the cervix of the uterus to the vest ibule of the vagina, the cleft between the labia minora into which the vagina and urethra open (Fig. 3.30). The vestibule contains the vaginal and external urethral orifices and the openings of the two greater vestibular glands. The superior end of the vagina surrounds the cervix of the uterus. The vagina: Serves as a canal for menstrual fluid. Forms the inferior part of the birth canal. Receives the penis and ejaculate during sexual intercourse. Communicates superiorly with the cervical canal, and inferiorly with the vestibule. The cervical canal extends from the isthmus of the uterus to the external os (opening) of the uterus. The vagina is usually collapsed, so its anterior and posterior walls are in contact, except at its superior end, where the cervix holds them apart. The vaginal fornix, the recess around the protruding cervix, is usually described as having anterior, posterior, and lateral parts. The posterior vaginal fornix is the deepest part and is closely related to the rectouterine pouch (Fig. 3.32B). FIGURE 3.31. Support ing and compressive muscles of female pelvis. Four muscles compress the vagina and act like sphincters: pubovaginalis, external urethral sphincter, urethrovaginal sphincter, and bulbospongiosus (Fig. 3.31). The relations of the vagina are: Anteriorly: the fundus of the urinary bladder and urethra. Laterally: the levator ani, visceral pelvic fascia, and ureters. Posteriorly (inferior to superior): the anal canal, rectum, and recto-uterine pouch (Fig. 3.4A). Vasculature of Vagina. The arteries supplying the superior part of the vagina derive from the uterine arteries; the arteries supplying the middle and inferior parts of the vagina derive from the vaginal arteries and internal pudendal arteries (Fig. 3.32A; Table 3.5). The veins form the vaginal venous plexuses along the sides of the vagina and within the vaginal mucosa (Fig. 3.32B). These veins communicate with the uterine venous plexus as the uterovaginal plexus and drain into the internal iliac veins through the uterine vein. The lymphatic vessels drain from the vagina as follows (Fig. 3.22; Table 3.6): Superior part: to the internal and external iliac lymph nodes. P.238 Middle part: to the internal iliac lymph nodes. Inferior part: to the sacral and common iliac nodes. External orifice: to the superficial inguinal lymph nodes. UTERUS The uterus (womb) is a thick-walled, pear-shaped, hollow muscular organ. The nongravid (not pregnant) uterus usually lies in the lesser pelvis, with its body lying on the urinary bladder and its cervix between the urinary bladder and the rectum (Fig. 3.33B). The adult uterus is usually anteverted (tipped anterosuperiorly relative to the axis of the vagina) and anteflexed (uterine body is flexed or bent anteriorly relative to the cervix) so that its mass lies over the bladder. The position of the uterus changes with the degree of fullness of the bladder and rectum. The uterus is divisible into two main parts (Fig. 3.33A): FIGURE 3.32. Vasculature of vagina, uterus, uterine tube, and ovary. A. Arterial supply. B. Venous drainage. Distent ion and Examinat ion of Vagina The vagina can be markedly distended by the fetus during childbirth, particularly in an anteroposterior direction. Lateral distention of the vagina is limited by the ischial spines, which project posteromedially, and the sacrospinous ligaments extending from these spines to the lateral margins of the sacrum and coccyx. The interior of the vagina can be distended for examination using a vaginal speculum (Fig. B3.4). The cervix, ischial spines, and sacral promontory can be palpated with the gloved digits in the vagina and/or rectum (manual pelvic examination). P.241 FIGURE 3.34. Uterus, uterine tubes, and broad ligament. A. Relationship of the broad ligament to the ovary and its ligaments. B. Sagittal sections showing the mesentery of the uterus (mesometrium), ovary (mesovarium), and uterine tube (mesosalpinx). Transverse cervical (cardinal) ligaments extend from the cervix and lateral parts of the fornix of the vagina to the lateral walls of the pelvis. Uterosacral ligaments pass superiorly and slightly posteriorly from the sides of the cervix to the middle of the sacrum (Fig. 3.8E); they are palpable on rectal examination. Relationships of Uterus. Peritoneum covers the uterus anteriorly and superiorly, except for the cervix (Figs. 3.6A,C and 3.34; Table 3.3). The peritoneum is reflected anteriorly from the uterus onto the bladder and posteriorly over the posterior part of the fornix of the vagina onto the rectum. Anteriorly, the uterine body is separated from the urinary bladder by the vesico-uterine pouch where the peritoneum is reflected from the uterus onto the posterior margin of the superior surface of the bladder (Fig. 3.33B); the inferior uterine body (isthmus) and cervix lie in direct contact with the bladder without intervening peritoneum. This allows uterine/cervical cancer to invade the urinary bladder. Posteriorly, the uterine body and the supravaginal part of the cervix are separated from the sigmoid colon by a layer of peritoneum and the peritoneal cavity and from the rectum by the recto-uterine pouch. Laterally, the uterine artery crosses the ureter superiorly, near the cervix, in the root of the broad ligament (Fig. 3.34B). Vasculature of Uterus. The arteries derive mainly from the uterine arteries, with potential collateral supply from the ovarian arteries (Figs. 3.11A and 3.32A; Table 3.5). The uterine veins run in the broad ligament, draining the uterine venous plexus formed on each side of the uterus and vagina (Fig. 3.32B). Veins from this plexus drain into the internal iliac veins. The uterine lymphatic vessels follow three main routes (Fig. 3.22 and Table 3.6): Most vessels from the uterine fundus and superior uterine body pass along the ovarian vessels to the lumbar (caval/aortic) lymph nodes, but some vessels pass along the round ligament of the uterus to the superficial inguinal lymph nodes. Vessels from most of the uterine body pass within the broad ligament to the external iliac lymph nodes. Vessels from the uterine cervix pass along the uterine vessels, within the transverse cervical ligaments, to the internal iliac lymph nodes and along the uterosacral ligaments to the sacral lymph nodes. Innervation of Vagina and Uterus. The innervation of the inferior part of the vagina is somatic, from the deep perineal nerve, a branch of the pudendal nerve. The innervation of most of the vagina and the entire uterus, however, is visceral. The nerves are derived from the uterovaginal nerve plexus, which travels with the uterine artery at the junction of the base of the peritoneal broad ligament and the superior part of the transverse cervical ligament (Fig. 3.35). The uterovaginal plexus is one of the pelvic plexuses that extend to the pelvic viscera from the inferior hypogastric plexus. Sympathetic, parasympathetic, and visceral afferent fibers pass through this plexus. Sympathetic innervation originates in the inferior thoracic spinal cord segments and passes through lumbar splanchnic nerves and the intermesenteric-hypogastric-pelvic series of plexuses. Parasympathetic innervation originates in the S2-S4 spinal cord segments and passes through the pelvic splanchnic nerves to the inferior hypogastric-uterovaginal plexus. Visceral afferent fibers, carrying pain sensation from the intraperitoneal uterine fundus and body, travel retrogradely with the sympathetic fibers to the lower thoracic- upper lumbar spinal ganglia; those from the subperitoneal uterine cervix and vagina (inferior to the pelvic pain line) travel with the parasympathetic fibers to the spinal sensory ganglia of S2-S4. All visceral afferent fibers from the uterus and vagina not concerned with pain (those conveying unconscious sensations) also follow the latter route. FIGURE 3.35. Autonomic innervat ion of uterus, vagina, and ovaries. Autonomic innervat ion of uterus, vagina, and ovaries. P.242 UTERINE TUBES The uterine tubes (formerly called fallopian tubes) extend laterally from the uterine horns and open into the peritoneal cavity near the ovaries (Figs. 3.33 and 3.34B). The uterine tubes lie in the mesosalpinx in the free edges of the broad ligament. In the “ideal” disposition, the tubes extend posterolaterally to the lateral pelvic walls, where they ascend and arch over the ovaries; however, ultrasound studies demonstrate that the position of the tubes and ovaries is variable (dynamic) in life, and right and left sides are often asymmetrical. FIGURE 3.35. (continued) Hysterectomy Hysterectomy (excision of the uterus) is performed through the lower anterior abdominal wall or through the vagina (Fig. B3.5). Because the uterine artery crosses anterior to the ureter near the lateral fornix of the vagina, the ureter is in danger of being inadvertently clamped or severed when the uterine artery is tied off during a hysterectomy. The point of crossing of the artery and the ureter is approximately 2 cm superior to the ischial spine. FIGURE B3.7. Regional anesthesia for childbirth. Manual Examinat ion of Uterus The size and disposition of the uterus may be examined by bimanual palpation (Fig. B3.8). Two gloved fingers of the examiner's dominant hand are passed superiorly in the vagina, while the other hand is pressed inferoposteriorly on the pubic region of the anterior abdominal wall. The size and other characteristics of the uterus can be determined in this way (e.g., whether the uterus is in its normal anteverted position). P.244 FIGURE B3.8. Each uterine tube is divisible into four parts (Fig. 3.34B): The infundibulum is the funnel-shaped distal end that opens into the peritoneal cavity through the abdominal ost ium. The finger-like processes of the infundibulum, the fimbriae, spread over the medial surface of the ovary; one large ovarian fimbria is attached to the superior pole of the ovary. The ampulla, the widest and longest part, begins at the medial end of the infundibulum. The isthmus, the thick-walled part, enters the uterine horn. The uterine part is the short intramural segment that passes through the wall of the uterus and opens through the uterine ost ium into the uterine cavity at the uterine horn (Fig. 3.33A). OVARIES The almond-shaped ovaries are typically located near the attachment of the broad ligament to the lateral pelvic walls, suspended from both by peritoneal folds, the mesovarium from the posterosuperior aspect of the broad ligament and the suspensory ligament of the ovary from the pelvic wall (Figs. 3.34A and 3.36A,B). The suspensory ligament conveys the ovarian vessels, lymphatics, and nerves to and from the ovary and constitutes the lateral part of the mesovarium. The ovary also attaches to the uterus by the ligament of ovary, which runs within the mesovarium. This ligament is a remnant of the superior part of the ovarian gubernaculum of the fetus and connects the proximal (uterine) end of the ovary to the lateral angle of the uterus, just inferior to the entrance of the uterine tube. Because the ovary is suspended in the peritoneal cavity and its surface is not covered by peritoneum, the oocyte expelled at ovulation passes into the peritoneal cavity but is usually trapped by the fimbriae of the uterine tube and carried to the ampulla. P.245 FIGURE 3.36. Imaging of female pelvis. A. and B. Structures seen on an ultrasound scan. C. and D. Structures seen via MRI. Vasculature of Ovaries and Uterine Tubes. The ovarian arteries arise from the abdominal aorta and descend along the posterior abdominal wall. At the pelvic brim, they cross over the external iliac vessels and enter the suspensory ligaments (Figs. 3.32A and 3.34B). The ovarian artery sends branches through the mesovarium to the ovary and through the mesosalpinx to supply the uterine tube. The ascending branches of the uterine arteries (branches of the internal iliac arteries) course along the lateral aspects of the uterus to approach the medial aspects of the ovaries and tubes. The ovarian and ascending uterine arteries terminate by bifurcating into ovarian and tubal branches and anastomose with each other, providing a collateral circulation from abdominal and pelvic sources. Ovarian veins draining the ovary form a pampiniform plexus of veins in the broad ligament near the ovary and uterine tube (Fig. 3.32B). The veins of the plexus merge to form a singular ovarian vein, which leaves the lesser pelvis with the ovarian artery. The right ovarian vein ascends to enter the inferior vena cava; the left ovarian vein drains into the left renal vein. The tubal veins drain into the ovarian veins and uterine (uterovaginal) venous plexus. The lymphatic vessels from the ovary join those from the uterine tubes and fundus of the uterus as they ascend to the right and left (caval/aortic) lumbar lymph nodes (Fig. 3.22 and Table 3.6). Innervation of Ovaries and Uterine Tubes. and communicates with the vesical venous plexus in males and the uterovaginal venous plexus in females. The rectal venous plexus consists of two parts, the internal rectal venous plexus just deep to the epithelium of the rectum and the external rectal venous plexus external to the muscular wall of the rectum. FIGURE 3.39. Lymphatic drainage of rectum and anal canal. Lymphatic vessels from the superior half of the rectum pass to the pararectal lymph nodes, located directly on the muscle layer of the rectum (Fig. 3.39), and then ascend to the inferior mesenteric lymph nodes either via the sacral lymph nodes or by passing through the nodes along the superior rectal vessels. Lymphatic vessels from the inferior half of the rectum drain into the sacral lymph nodes or, especially from the distal ampulla, follow the middle rectal vessels to drain into the internal iliac lymph nodes. Infect ions of Female Genital Tract Because the female genital tract communicates with the peritoneal cavity through the abdominal ostia of the uterine tubes, infections of the vagina, uterus, and uterine tubes may result in peritonitis. Conversely, inflammation of the tubes (salpingitis) may result from infections that spread from the peritoneal cavity. A major cause of infertility in women is blockage of the uterine tubes, often the result of infection that causes salpingitis. Patency of Uterine Tubes Patency of the uterine tubes may be determined by a radiographic procedure involving injection of a water-soluble radiopaque material or carbon dioxide gas into the uterus, hysterosalpingography. The material enters the uterine tubes and, if the tubes are patent, passes from the abdominal ostium into the peritoneal cavity (Fig. B3.9). Patency can also be determined by hysteroscopy, examination of the interior of the tubes using an endoscopic instrument (hysteroscope) introduced through the vagina and uterus. FIGURE B3.9. Laparoscopic Examinat ion of Pelvic Viscera Laparoscopy involves inserting a laparoscope into the peritoneal cavity through a small incision below the umbilicus (Fig. B3.10). Insufflation of inert gas creates a pneumoperitoneum to provide space to visualize the pelvic organs. Additional openings (ports) can be made to introduce other instruments for manipulation or to enable therapeutic procedures (e.g., ligation of the uterine tubes). FIGURE B3.10. Ligat ion of Uterine Tubes Ligation of the uterine tubes is a surgical method of birth control. Abdominal tubal ligat ion is usually performed through a short suprapubic incision made just at the pubic hairline. Laparoscopic tubal ligat ion is done with a laparoscope, which is similar to a small telescope with a powerful light. It is inserted through a small incision, usually near the umbilicus. Ectopic Tubal Pregnancy Occasionally, a blastocyst fails to reach the uterus and may implant in the mucosa of the uterine tube (most commonly the ampulla), producing an ectopic tubal pregnancy. On the right side, the appendix often lies close to the ovary and uterine tube. This close relationship explains why a ruptured tubal pregnancy and the PERINEUM The term “perineum” is frequently used to refer to both an external surface area (perineal region) and a shallow “compartment” of the body (Fig. 3.41). The perineum (perineal compartment) lies inferior to the inferior pelvic aperture and is separated from the pelvic cavity by the pelvic diaphragm. In the anatomical position, the surface of the perineum (perineal region ) is the narrow region between the proximal parts of the thighs. However, when the lower limbs are abducted, the perineal region is a diamond- shaped area extending from the mons pubis anteriorly, the medial surfaces (insides) of the thighs laterally, and the gluteal folds and superior end of the intergluteal (natal) cleft posteriorly (Fig. 3.43A). The osseofibrous structures marking the boundaries of the perineum (perineal compartment) are the (Fig. 3.42): Pubic symphysis, anteriorly. Inferior pubic and ischial (ischiopubic) rami, anterolaterally. Ischial tuberosities, laterally. Sacrotuberous ligaments, posterolaterally. Inferiormost sacrum and coccyx, posteriorly. A transverse line joining the anterior ends of the ischial tuberosities divides the perineum into two triangles (Fig. 3.42A): The anal t riangle lies posterior to this line and contains the anal canal and its orifice, the anus. The urogenital (UG) triangle, containing the root of the scrotum and penis in males and the vulva of females, is anterior to this line. The UG triangle is “closed” by the perineal membrane (Fig. 3.43C), a thin sheet of tough deep fascia, which stretches between the right and the left sides of the pubic arch. The perineal membrane covers the anterior part of the pelvic outlet and is perforated by the urethra in both sexes and by the vagina of the female. The perineal body is an irregular fibromuscular mass located in the median plane between the anal canal and the perineal membrane. It lies deep to the skin, with relatively little overlying subcutaneous tissue, posterior to the vestibule of the vagina or bulb of the penis and anterior to the anus and anal canal. Anteriorly, the perineal body blends with the posterior border of the perineal membrane and superiorly with the rectovesical or rectovaginal septum. It contains collagenous and elastic fibers and both skeletal and smooth muscle. FIGURE 3.41. Perineum and perineal region. The perineal body is the site of convergence of several muscles (Fig. 3.43B and Table 3.9): Bulbospongiosus. External anal sphincter. Superficial and deep transverse perineal muscles. Smooth and voluntary slips of muscle from the external urethral sphincter, levator ani, and muscular coats of the rectum. [oral ds oa] Po o LO Ses symphysis [Ee air: LEA tuberosity A Inferior (arcuate) pubic ligament Ischiopubic, nf am À P e Rã Pubic symphysis | 4 Pelvic outlet À ts (inferior pelvic aperture) » ” Isehial tuberosity 3 E encroté ca o AR AO E ligaments ad O” a B Female pelvis, inferior views (lithotomy position) FIGURE 3.42. Osseoligamentous boundaries of perineum. and cavernosa, and fascia of bulb of penis Female: passes on each side of lower vagina, enclosing bulb and greater vestibular gland; inserts onto pubic arch and fascia of corpora cavernosa of clitoris blood from bulb into body of penis Female: “sphincter” of vagina; assists in erection of clitoris (and bulb of vestibule); compresses greater vestibular gland Ischiocavernosus Internal surface of ischiopubic ramus and ischial tuberosity Embraces crus of penis or clitoris, inserting onto inferior and medial aspects of crus and to perineal membrane medial to crus Muscular (deep) branch of perineal nerve, branch of pudendal nerve Maintains erection of penis or clitoris by compressing outflow veins and pushing blood from root of penis or clitoris into body Superfic ia l transverse perineal Internal surface of ischiopubic ramus and ischial tuberosity; compressor urethrae Passes along superior posterior border of perineal membrane to perineal body Muscular (deep) branch of perineal nerve, branch of pudendal nerve (S2- S4); dorsal nerve of penis or clitoris, terminal Support and fix perineal body (pelvic floor) to support abdominopelvic viscera and resist increased intra-abdominal pressure Deep transverse perineal Passes along superior posterior border of perineal membrane to perineal body, and external anal sphincter External urethral Surrounds Compresses P.253 sphincter portion only urethra superior to perineal membrane Male: also ascends anterior aspect of prostate Female: some fibers also enclose vagina (urethrovaginal sphincter) branch of pudendal nerve (S2- S4) urethra to maintain urinary continence Female: urethrovaginal sphincter portion alsocompresses vagina Disrupt ion of Perineal Body The perineal body is an especially important structure in women because it is the final support of the pelvic viscera. Stretching or tearing of this attachment of the perineal muscles from the perineal body can occur during childbirth, removing support provided by the pelvic floor. As a result, prolapse of pelvic viscera, including prolapse of the bladder (through the urethra) and prolapse of the uterus and/or vagina (through the vaginal orifice), may occur. Episiotomy During vaginal surgery and labor, an episiotomy (surgical incision of the perineum and inferoposterior vaginal wall) may be made to enlarge the vaginal orifice with the intention of decreasing excessive tearing of the perineum and perineal muscles. Episiotomies are still performed in a large portion of vaginal deliveries. It is generally agreed that episiotomy is indicated when descent of the fetus is arrested or protracted, when instrumentation is necessary (e.g., obstetrical forceps), or to expedite delivery when there are signs of fetal distress. However, routine prophylactic episiotomy is widely debated and declining in frequency. Fascias and Pouches of Urogenital Triangle PERINEAL FASCIAS The perineal fascia consists of superficial and deep layers (Fig. 3.44). The subcutaneous t issue of the perineum, or superficial perineal fascia, consists of a fatty superficial layer and a deep membranous layer (Colles fascia). In females, the fat ty layer of subcutaneous t issue of the perineum makes up the substance of the labia majora and mons pubis and is continuous anteriorly and superiorly with the fatty layer of subcutaneous tissue of the abdomen (Camper fascia) (Fig. 3.44A,C). In males, the fatty layer is greatly diminished in the urogenital triangle and is replaced altogether in the penis and scrotum with smooth (dartos) muscle. It is continuous between the penis or scrotum and the thighs with the fatty layer of subcutaneous tissue of the abdomen (Fig. 3.44B,F). In both sexes, it is continuous posteriorly with the ischio-anal fat pad in the anal region (Fig. 3.44E). The membranous layer of subcutaneous t issue of the perineum is attached posteriorly to the posterior margin of the perineal membrane and the perineal body (Fig. 3.44A,B). Laterally, it is attached to the fascia lata (deep fascia) of the superiormost medial aspect of the thigh. Anteriorly, in the male, the membranous layer of subcutaneous tissue is continuous with the dartos fascia of the penis and scrotum; however, on each side of and anterior to the scrotum, the membranous layer becomes continuous with the membranous layer of subcutaneous tissue of the abdomen (Scarpa fascia) (Fig. 3.44B,F). In females, the membranous layer passes superior to the fatty layer forming the labia majora and becomes continuous with the membranous layer of the subcutaneous tissue of the abdomen (Fig. 3.44A,C). The perineal fascia (deep perineal, investing, or Gallaudet fascia) intimately invests the ischiocavernosus, bulbospongiosus, and superficial transverse perineal muscles (Fig. 3.44C,D). It is also attached laterally to the ischiopubic rami. Anteriorly, it is fused to P.254 the suspensory ligament of the penis and is continuous with the deep fascia covering the external oblique muscle of the abdomen and the rectus sheath. The deep perineal fascia is fused with the suspensory ligament of the clitoris in females and with the deep fascia of the abdomen in males. SUPERFICIAL PERINEAL POUCH The superfic ia l perineal pouch (compartment) is a potential space between the membranous layer of subcutaneous tissue and the perineal membrane, bounded laterally by the ischiopubic rami (Fig. 3.44A-D). In males, the superficial perineal pouch contains the (Fig. 3.44B,D): Root (bulb and crura) of the penis and associated muscles (ischiocavernosus and bulbospongiosus). Proximal (bulbous) part of the spongy urethra. Superficial transverse perineal muscles. Deep perineal branches of the internal pudendal vessels and pudendal nerves. In females, the superficial perineal pouch contains the (Fig. 3.44A,C): Clitoris and associated muscle (ischiocavernosus). Bulbs of the vestibule and the surrounding muscle (bulbospongiosus). Greater vestibular glands. Deep perineal branches of the internal pudendal vessels and pudendal nerves. Superficial transverse perineal muscles. DEEP PERINEAL POUCH The deep perineal pouch (space) is bounded inferiorly by the perineal membrane, superiorly by the inferior fascia of the pelvic diaphragm, and laterally by the inferior portion of the obturator fascia (covering obturator internus muscle). It includes the fat-filled anterior recesses of the ischio-anal fossa (Figs. 3.44C,D and Fig. 3.46). In both sexes, the deep perineal pouch contains part of the urethra centrally, the inferior part of the external urethral sphincter muscle, and the anterior extensions of the ischio-anal fat pads. In males, the deep perineal pouch contains the intermediate part of the urethra, deep transverse perineal muscles, bulbourethral glands, and dorsal neurovascular structures of the penis (Fig. 3.44D). In females, it contains the proximal part of the urethra, a mass of smooth muscle in place of deep transverse perineal muscles, and the dorsal neurovasculature of the clitoris (Fig. 3.44C). P.256 Rupture of Urethra in Males and Extravasat ion of Urine Fractures of the pelvic girdle often cause a rupture of the intermediate part of the urethra. This results in extravasation of urine and blood into the deep perineal pouch (Fig. B3.11A). The fluid may pass superiorly through the urogenital hiatus and distribute extraperitoneally around the prostate and bladder. Rupture of the spongy urethra in the bulb of the penis results in urine passing (extravasating) into the superficial perineal space (Fig. B3.11B). The attachments of the perineal fascia determine the direction of flow of the extravasated urine. Urine and blood may pass into the loose connective tissue in the scrotum, around the penis, and superiorly, deep to the membranous layer of subcutaneous connective tissue of the inferior anterior abdominal wall. The urine cannot pass far into the thighs because the membranous layer of superficial perineal fascia blends with the fascia lata (deep fascia) enveloping the thigh muscles, just distal to the inguinal ligament. In addition, urine cannot pass posteriorly into the anal triangle because the superficial and deep layers of perineal fascia are continuous with each other around the superficial perineal muscles and with the posterior edge of the perineal membrane between them. FIGURE B3.11. P.257 Features of Anal Triangle ISCHIO-ANAL FOSSAE The ischio-anal fossae (formerly ischiorectal fossae) around the wall of the anal canal are large fascia-lined, wedge-shaped spaces between the skin of the anal region and the pelvic diaphragm (Fig. 3.46). The apex of each fossa lies superiorly where the levator ani muscle arises from the obturator fascia. The ischio-anal fossae, wide inferiorly and narrow superiorly, are filled with fat and loose connective tissue. The two ischio-anal fossae communicate by means of the deep postanal space over the anococcygeal ligament (body), a fibrous mass located between the anal canal and the tip of the coccyx (Fig. 3.46A). Each ischio-anal fossa is bounded (Fig. 3.46A,B): Laterally by the ischium and the inferior part of the obturator internus, covered with obturator fascia. Medially by the external anal sphincter, with a sloping superior medial wall or roof formed by the levator ani as it descends to blend with the sphincter; both structures surround the anal canal. Posteriorly by the sacrotuberous ligament and gluteus maximus. Anteriorly by the bodies of the pubic bones, inferior to the origin of the puborectalis; these parts of the fossae, extending into the UG triangle superior to the perineal membrane, are known as the anterior recesses of the ischio-anal fossae. FIGURE 3.46. Pelvic diaphragm and ischio-anal fossae. A. Pelvic diaphragm. Arrow passes through deep postanal space. B. Section of the pelvis through the rectum, anal canal, and ischio-anal fossae. The ischio-anal fossae are traversed by tough, fibrous bands and filled with fat, forming the fat bodies of the ischio-anal fossae. These fat bodies support the anal canal but are readily displaced to permit expansion of the anal canal during the passage P.258 P.259 of feces. The fat bodies are traversed by several neurovascular structures, including the inferior anal/rectal vessels and nerves and two other cutaneous nerves: the perforating branch of S2 and S3 and the perineal branch of the S4 nerve. FIGURE 3.47. Pudendal nerve. The five regions in which the nerve runs are color-coded. In females, the superficial perineal nerve gives rise to posterior labial nerves and the terminal branch of the pudendal nerve is the dorsal nerve of the clitoris. PUDENDAL CANAL The pudendal canal (Alcock canal) is essentially a horizontal passageway within the obturator fascia (Figs. 3.46B and 3.47), which covers the medial aspect of the obturator internus muscle and lines the lateral wall of the ischio-anal fossa. The pudendal canal begins at the posterior border of the ischio-anal fossa and runs from the lesser sciatic notch adjacent to the ischial spine to the posterior edge of the perineal membrane. The internal pudendal artery and vein, the pudendal nerve, and the nerve to the obturator internus enter this canal at the lesser sciatic notch, inferior to the ischial spine. The internal pudendal vessels supply and drain blood from the perineum; the pudendal nerve innervates most of the same area. As the artery and nerve enter the canal, they give rise to the inferior anal (rectal) artery and nerve that pass medially to supply the external anal sphincter and perianal skin. Toward the distal (anterior) end of the pudendal canal, the artery and nerve both bifurcate, giving rise to the perineal nerve and artery, which are distributed mostly to the superficial pouch (inferior to the perineal membrane) and to the dorsal artery and nerve of the penis or clitoris, which run in the deep pouch (superior to the membrane). The perineal nerve has two branches: the superfic ia l perineal nerves give rise to posterior scrotal or labial (cutaneous) branches, and the deep perineal nerve supplies the muscles of the deep and superficial perineal pouches, the skin of the vestibule of the vagina, and the mucosa of the inferiormost part of the vagina. The dorsal nerve of the penis or clitoris is the primary sensory nerve serving the male or female organ, especially the glans. Ischio-anal Abscesses The ischio-anal fossae are occasionally the sites of infection, which may result in the formation of ischioanal abscesses (Fig. B3.12). These collections of pus are painful. Diagnostic signs of an ischio-anal abscess are fullness and tenderness between the anus and the ischial tuberosity. A perianal abscess may rupture spontaneously, compressed by the contracted sphincters, impeding blood flow. As a result, they tend to strangulate and ulcerate. Owing to the presence of abundant arteriovenous anastomoses, bleeding from internal hemorrhoids is usually bright red. External hemorrhoids are thromboses (blood clots) in the veins of the external rectal venous plexus and are covered by skin. Predisposing factors for hemorrhoids include pregnancy, chronic constipation, and any disorder that impedes venous return, including increased intra-abdominal pressure. The anastomoses among the superior, middle, and inferior rectal veins form clinically important communications between the portal and the systemic venous systems (Fig. 3.48). The superior rectal vein drains into the inferior mesenteric vein, whereas the middle and inferior rectal veins drain through the systemic system into the inferior vena cava. Any abnormal increase in pressure in the valveless portal system or veins of the trunk may cause enlargement of the superior rectal veins, resulting in increase in blood flow or stasis in the internal rectal venous plexus. In portal hypertension, as in hepatic cirrhosis, the portocaval anastomosis among the superior, middle, and inferior rectal veins, along with portocaval anastomoses elsewhere, may become varicose. It is important to note that the veins of the rectal plexuses normally appear varicose (dilated and tortuous) and that internal hemorrhoids occur most commonly in the absence of portal hypertension. Because visceral afferent nerves supply the anal canal superior to the pectinate line, an incision or a needle insertion in this region is painless. However, the anal canal inferior to the pectinate line is quite sensitive (e.g., to the prick of a hypodermic needle) because it is supplied by the inferior rectal nerves, containing somatic sensory fibers. FIGURE B3.13. Innervation of Anal Canal. The nerve supply to the anal canal superior to the pectinate line is visceral innervation from the inferior hypogastric plexus (sympathetic, parasympathetic, and visceral afferent fibers) (Figs. 3.40 and 3.48). The superior part of the anal canal is inferior to P.261 the pelvic pain line; all visceral afferents travel with the parasympathetic fibers to spinal sensory ganglia S2-S4. Superior to the pectinate line, the anal canal is sensitive only to stretching. The nerve supply of the anal canal inferior to the pectinate line is somatic, derived from the inferior anal (rectal) nerves, branches of the pudendal nerve. Therefore, this part of the anal canal is sensitive to pain, touch, and temperature. Somatic efferent fibers stimulate the contraction of the voluntary external anal sphincter. Male Perineum The male perineum includes the external genitalia (urethra, scrotum, and penis), perineal muscles, and anal canal. DISTAL MALE URETHRA The urethra in the bladder neck (intramural part) and the prostatic urethra, the first two parts of the male urethra, are described with the pelvis (Fig. 3.25 and Table 3.8). The intermediate (membranous) part of the urethra begins at the apex of the prostate and traverses the deep perineal pouch, surrounded by the external urethral sphincter. It then penetrates the perineal membrane, ending as the urethra enters the bulb of the penis (Fig. 3.18). Posterolateral to this part of the urethra are the small bulbourethral glands (Figs. 3.18 and 3.20A) and their slender ducts, which open into the proximal part of the spongy urethra. The spongy urethra begins at the distal end of the intermediate part of the urethra and ends at the external urethral orifice (Figs. 3.18 and 3.49B,D). The lumen of the spongy urethra is expanded in the bulb of the penis to form the intrabulbar fossa and in the glans of the penis to form the navicular fossa. On each side, the ducts of the bulbourethral glands open into the proximal part of the spongy urethra. There are also many minute openings of the ducts of mucus-secreting urethral glands (Littré glands) into the spongy urethra. The arterial supply of the intermediate and spongy parts of the urethra is from branches of the dorsal artery of the penis (Fig. 3.50B). The veins accompany the arteries and have similar names. Lymphatic vessels from the intermediate part of the urethra drain mainly into the internal iliac lymph nodes (Fig. 3.51), whereas most vessels from the spongy urethra pass to the deep inguinal lymph nodes, but some vessels pass to the external iliac lymph nodes. The innervation of the intermediate part of the urethra is the same as that of the prostatic part (Fig. 3.52). The dorsal nerve of the penis, a branch of the pudendal nerve, provides somatic innervation of the spongy part of the urethra. Urethral Catheterizat ion Urethral catheterizat ion is done to remove urine from a person who is unable to micturate. It is also performed to irrigate the bladder and to obtain an uncontaminated sample of urine. When inserting the catheters and urethral sounds (slightly conical instruments for exploring and dilating a constricted urethra) the curves of the male urethra must be considered. SCROTUM The scrotum is a cutaneous fibromuscular sac for the testes and associated structures. It is situated posteroinferior to the penis and inferior to the pubic symphysis (Fig. 3.49). The bilateral embryonic formation of the scrotum is indicated by the midline scrotal raphe (Fig. 3.49C), which is continuous on the ventral surface of the penis with the penile raphe and posteriorly along the median line of the perineum as the perineal raphe. Internally deep to the scrotal raphe, the scrotum is divided into two compartments, one for each testis, by a prolongation of dartos fascia, the septum of the scrotum. The contents of the scrotum (testes and epididymides) are described with the abdomen (see Chapter 2). Vasculature of Scrotum. The anterior aspect of the scrotum is supplied by the anterior scrotal arteries, terminal branches of the external pudendal arteries (Fig. 3.50B and Table 3.10), and the posterior aspect is supplied by the posterior scrotal arteries, terminal branches of the internal pudendal arteries. The scrotum also receives branches from the cremasteric arteries, branches of inferior epigastric arteries. The scrotal veins accompany the arteries and drain primarily to the external pudendal veins. Lymphatic vessels from the scrotum drain into the superficial inguinal lymph nodes (Fig. 3.51). Innervation of Scrotum. The anterior aspect of the scrotum is supplied by the anterior scrotal nerves derived from the ilio-inguinal nerve, and by the genital branch of the genitofemoral nerve. The posterior aspect of the scrotum is supplied by posterior scrotal nerves, P.262 branches of the superficial perineal branches of the pudendal nerve (Fig. 3.52), and by the perineal branch of the posterior femoral cutaneous nerve. PENIS The penis is the male organ of copulation and the outlet for urine and semen. The penis consists of a root, body, and glans penis (Fig. 3.49D). It is composed of three cylindrical bodies of erectile cavernous tissue: the paired corpora cavernosa and the single corpus spongiosum ventrally. (Note that in the anatomical position, the penis is erect; when the penis is flaccid, its dorsum is directed anteriorly.) Each cavernous body has a fibrous outer covering or capsule, the tunica albuginea (Fig. 3.49B). Superficial to the outer covering is the deep fascia of the penis (Buck fascia), the continuation of the deep perineal fascia that forms a membranous covering for the corpora, binding them together. The corpus spongiosum contains the spongy urethra. The corpora cavernosa are fused with each other in the median plane except posteriorly, where they separate to form the crura of the penis (Figs. 3.49A and 3.53). The root of the penis consists of the crura, bulb, and ischiocavernosus and bulbospongiosus muscles (Fig. 3.53; Table 3.9). The root is located in the superficial perineal pouch (Fig. 3.44B,D). The crura and bulb of the penis contain masses of erectile tissue. Each crus is attached to the inferior part of the internal surface of the corresponding ischial ramus, anterior to the ischial tuberosity. The bulb of the penis is penetrated by the urethra, continuing from its intermediate part. P.265 FIGURE 3.50. Arteria l supply of perineum. Superficial and deep dissections of male perineum. Lymph from the skin of the penis drains initially to the superficial inguinal lymph nodes, and lymph from the glans and distal spongy urethra drains to the deep inguinal and external iliac nodes. The cavernous bodies and proximal spongy urethra drain to the internal iliac nodes (Fig. 3.51). Innervation of Penis. The nerves derive from the S2-S4 segments of the spinal cord. Sensory and sympathetic innervation is primarily from the dorsal nerve of the penis, a terminal branch of the pudendal nerve (Fig. 3.52), which arises in the pudendal canal and passes anteriorly into the deep perineal pouch. It then runs along the dorsum of the penis lateral to the dorsal artery and supplies the skin and glans. The penis is supplied with a variety of sensory nerve endings, especially the glans penis. Branches of the ilioinguinal nerve supply the skin at the root of the penis. Cavernous nerves, conveying parasympathetic fibers independently from the prostatic nerve plexus, innervate the helicine arteries. Erection, Emission, Ejaculation, and Remission. Most of the time, the penis is flaccid. In this state, most arterial blood bypasses the “empty” potential spaces or sinuses of the corpora cavernosa by means of arteriovenous anastomoses. Only enough blood to bring oxygen and nutrition to the tissues circulates through the sinuses. When a male is stimulated erotically, parasympathetic stimulation by the cavernous nerves (conveying fibers from S2-S4 spinal cord levels via the prostatic nerve plexus) closes the arteriovenous anastomoses. Simultaneously, the tonic contraction of the smooth muscle in the fibrous trabeculae and coiled helicine arteries (terminal branches of the arteries serving the erectile tissue) is inhibited. As a result, the arteries straighten, enlarging their lumina. Blood flow no longer diverted from the cavernous spaces increases in volume, filling the sinuses of the corpora of the penis. The bulbospongiosus and ischiocavernosus muscles reflexively contract, compressing the veins of the corpora cavernosa, impeding the return of venous blood. Erect ion occurs as the corpora cavernosa and corpus spongiosum become engorged with blood at arterial pressure, causing the erectile bodies to become turgid (enlarged and rigid), elevating the penis. During emission, semen (sperms and glandular secretions) is delivered to the prostatic urethra through the ejaculatory ducts after peristalsis of the ductus deferentes and seminal glands. Prostatic fluid is added to the seminal fluid as the smooth muscle in the prostate contracts. Emission is a sympathetic response (L1-L2 nerves). P.266 FIGURE 3.51. Lymphatic drainage of male perineum. During ejaculat ion, semen is expelled from the urethra through the external urethral orifice. Ejaculation results from: Closure of the internal urethral sphincter at the neck of the urinary bladder, a sympathetic response (L1-L2 nerves) preventing retrograde ejaculation into the bladder. Contraction of the urethral muscle, a parasympathetic response (S2-S4 nerves). Contraction of the bulbospongiosus muscles, from the pudendal nerves (S2-S4). After ejaculation, the penis gradually returns to a flaccid state (remission), resulting from sympathetic stimulation that opens the arteriovenous anastomoses and causes contraction of smooth muscle of the helicine arteries, recoiling them. This reduces blood inflow as the bulbospongiosus and ischiocavernosus muscles relax, allowing more blood to be drained from the cavernous spaces into the deep dorsal vein. P.268 FIGURE 3.53. Superfic ia l and deep dissect ions of male perineum. Female Perineum The female perineum includes the female external genitalia, perineal muscles, and anal canal. FEMALE EXTERNAL GENITALIA The female external genitalia include the mons pubis, labia majora (enclosing the pudendal cleft), labia minora (enclosing the vestibule), clitoris, bulbs of the vestibule, and greater and lesser vestibular glands. The synonymous terms pudendum and vulva include all these parts. The term pudendum is commonly used clinically (Fig. 3.54). The pudendum vulva serves as sensory and erectile tissue for sexual arousal and intercourse, directs the flow of urine, and prevents entry of foreign material into the urogenital tract. Mons Pubis. The mons pubis is the rounded fatty eminence anterior to the pubic symphysis, pubic tubercle, and superior pubic rami. The amount of fat in the mons increases at puberty and decreases after menopause. After puberty, the mons pubis is covered with coarse pubic hairs (Fig. 3.54A). Labia Majora. The labia majora are prominent folds of skin that bound the pudendal c left , the slit between the labia majora, and indirectly provide protection for the urethral and vaginal orifices. Each labium majus—largely filled with subcutaneous fat containing smooth muscle and the termination of the round ligament of the uterus—passes inferoposteriorly from the mons pubis toward the anus. The external aspects of the labia in the adult are covered with pigmented skin containing many sebaceous glands and are covered with crisp pubic hair. The internal aspects of the labia are smooth, pink, and hairless. The labia are thicker anteriorly where they join to form the anterior commissure. Posteriorly, they merge to form the posterior commissure, which usually disappears after the first vaginal birth. FIGURE 3.54. Female perineum. A. Surface anatomy and perineal muscles. B. Structures on section. AD, adductor muscles of thigh; G, gluteus maximus; I, ischium; IF, ischio-anal fossa; LA, levator ani; M, mons pubis; S, external anal sphincter; R, rectum; V, vagina. Labia Minora. P.269 The labia minora are folds of fat-free, hairless skin. They have a core of spongy connective tissue containing erectile tissue and many small blood vessels. Although the internal surface of each labium minus consists of thin moist skin, it has the typical pink color of a mucous membrane and contains many sensory nerve endings. The labia minora are enclosed in the pudendal cleft within the labia majora and surround the vestibule into which the external urethral and vaginal orifices open. Anteriorly, the labia minora form two laminae: the medial laminae unite as the frenulum of the clitoris, and the lateral laminae unite to form the prepuce of the clitoris (Fig 3.54). In young women, especially virgins, the labia minora are connected posteriorly by a small transverse fold, the frenulum of the labia minora (fourchette). Clitoris. The clitoris is an erectile organ located where the labia minora meet anteriorly. The clitoris consists of a root and a body, which are composed of two crura, two corpora cavernosa, and the glans of the clitoris. The glans is covered by the prepuce of the clitoris (Figs. 3.54A and 3.55A). The clitoris is highly sensitive and enlarges on tactile stimulation. The glans is the most highly innervated part of the clitoris.
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