Pelvic Fascia PDF

8 Pelvis, Part I: Pelvic Walls For additional ancillary materials related to this chapter, please visit thePoint. A 51-year-old man was involved in a light-plane accident. He was flying home from a business trip when, because of fog, he had to make a forced landing in a plowed f...

8 Pelvis, Part I: Pelvic Walls For additional ancillary materials related to this chapter, please visit thePoint. A 51-year-old man was involved in a light-plane accident. He was flying home from a business trip when, because of fog, he had to make a forced landing in a plowed field. On landing, the plane came abruptly to rest on its nose. His companion was killed on impact, and he was thrown from the cockpit. On admission to the emergency department, he was unconscious and showed signs of severe hypovolemic (loss of circulating blood) shock. He had extensive bruising of the lower part of the anterior abdominal wall, and the front of his pelvis was prominent on the right side. During examination of the penis, a drop of blood-stained fluid was expressed from the external orifice. No evidence of external hemorrhage was present. Radiographic examination of the pelvis showed a dislocation of the symphysis pubis and a linear fracture through the lateral part of the sacrum on the right side. The urethra was damaged by the shearing forces applied to the pelvic area, which explained the blood-stained fluid from the external orifice of the penis. The pelvic radiograph (later confirmed on computed tomography scan) also revealed the presence of a large collection of blood in the loose connective tissue outside the peritoneum, which was caused by the tearing of the large, thin-walled pelvic veins by the fractured bone and accounted for the hypovolemic shock. This patient illustrates the fact that in-depth knowledge of the anatomy of the pelvic region is necessary before a physician can even contemplate making an initial examination and start treatment in cases of pelvic injury. CHAPTER OUTLINE Overview Pelvis Pelvic Orientation False Pelvis True Pelvis Pelvic Walls Pelvic Diaphragm Pelvic Joints Biologic Sex Differences Pelvic Fascia Parietal Pelvic Fascia Visceral Pelvic Fascia Pelvic Peritoneum Pelvic Nerves Lumbar Plexus Sacral Plexus Autonomic Nerves Pelvic Arteries Common Iliac Artery External Iliac Artery True Pelvis Arteries Pelvic Veins Pelvic Lymphatics Surface Anatomy Iliac Crest Pubic Tubercle and Crest Symphysis Pubis Sacrum and Coccyx Urinary Bladder Uterus Rectal and Vaginal Examinations Radiographic Anatomy LEARNING OBJECTIVES The purpose of this chapter is to review the significant anatomy of the pelvic walls relative to clinical problems. Particular attention is paid to age and sexual differences and to the anatomic features associated with pelvic examinations: 1. Identify the bones of the pelvis and their major features in the context of the composition of the pelvic walls. Describe the functional aspects of these structures. 2. Identify the bony components, major supporting ligaments, key accessory structures (e.g., intra-articular discs), and movements permitted at the joints of the pelvis. Relate these to the general mechanics of the pelvis. 3. Identify the specialized pelvic differences between males and females. Relate these to the mechanics of the pelvis, including the construction of the birth canal. 4. Identify the pelvic diaphragm, its components, and their innervation and basic functions. Indicate differences between males and females with respect to relationships to the urogenital tracts. 5. Identify the pelvic fasciae and peritoneum. Describe their relations with the abdominal fasciae and peritoneum. 6. Identify the lumbosacral plexuses, their segmental origins, and their major peripheral branches. Identify the sources of autonomic innervation to the pelvis. Describe the functional consequences of lesions of the main peripheral nerves. 7. Trace the flow of blood into and out of the pelvis by describing the courses, branching patterns, and distributions of the common iliac, external iliac, and internal iliac vessels. Note the relations of these vessels to neighboring organs, mesenteries, and neurovascular structures. 8. Trace the primary drainage routes through the pelvis. 9. Locate the surface projections and palpation points of major pelvic structures in a basic surface anatomy examination. 10. Identify the major structures of the pelvis in radiographic and cross- sectional images.  pelis-loosely used to describe the region where the trunk and lower limbs meet - means "basin" and is more correctly applied to the skeleton of the region the weight of the body From the vertebral column OVERVIEW - transmit The pelvis is the region of the trunk that lies inferior to the abdomen. Although the abdominal and pelvic cavities are continuous, the two regions usually are described separately. The term pelvis is loosely used to describe the region where the trunk and lower limbs meet. The word pelvis means “basin” and is more correctly applied to the skeleton of the region, that is, the pelvic girdle or bony pelvis. Thus, the pelvis is a bowl-shaped bony structure. The main function of the bony pelvis is to transmit the weight of the body from the vertebral column to the femurs. In addition, it contains, supports, and protects the lower parts of the gastrointestinal and urinary tracts and the male and female internal organs of reproduction. It also contains important nerves, blood vessels, and lymphatic tissues and provides attachment for trunk and lower limb muscles. Four bones make up the bony pelvis: the two hip bones (os coxae), which form the lateral and anterior walls, and the sacrum and the coccyx, which are part of the vertebral column and form the posterior wall (Fig. 8.1).The two hip bones articulate with each other anteriorly at the symphysis pubis and posteriorly with the sacrum at the sacroiliac joints. The bony pelvis thus forms a strong basin-shaped structure. 4 bones make up the bany pelvis : (os coxae) From the lateral & anterior walls 2 hip bones -. sacrum - coccyx - symphysis pubis-where I hip bones articulate w) each other anteriorly sacroiliac joints - posteriorly wh the sacroiliac joint  1 Pubis Figure 8.1 Anterior view of the male pelvis (A) and female pelvis (B). PELVIS pelvic brim - Formed by the sacral promontory behind & ileopectineal lines laterally & symphysis publis anteriorly  False Pelvis (greater) - bounds the lower part of the abdominal carity true Pelvis /lesser) - contains pelvic cavity , is below the brim The pelvic brim divides the pelvis into two parts. The pelvic brim is formed by the sacral promontory (anterior and upper margin of the first sacral vertebra) behind, the iliopectineal lines (lines that run downward and forward around the inner surface of the ileum) laterally, and the symphysis pubis (joint between the bodies of the pubic bones) anteriorly. The false pelvis, which bounds the lower part of the abdominal cavity, is above the brim. The true pelvis, which contains the pelvic cavity, is below the brim. Pelvic Orientation Understand that the correct orientation of the bony pelvis relative to the trunk is with the individual standing in the anatomic position. The front of the symphysis pubis and the anterior superior iliac spines lie in the same vertical plane. This means that the pelvic surface of the symphysis pubis faces upward and backward and the anterior surface of the sacrum is directed forward and downward. pelvic of the surface symphysis publis upward & backward UB - anterior surface of the sacrum-directed forward & downward False Pelvis Ed The false pelvis is of little clinical importance. The boundaries are the lumbar vertebrae behind, the iliac fossae and the iliacus muscles laterally, and the lower part of the anterior abdominal wall in front. The false pelvis flares out at its upper end and is considered part of the abdominal cavity. It supports the abdominal contents and, after the 3rd month of pregnancy, helps support the gravid uterus. During the early stages of labor, it helps guide the fetus into the true pelvis. Boundaries LU behind pregnancy helps - 3rd month of - iliac Fossa & iliacus muscle laterally the support the uterus - gravid of True Pelvis lower part of AAW in front - during early stages of labor helps - , guide the Fetus into the true pelvis The anatomy of the true pelvis in females is important for obstetrics because it forms the bony canal through which the child passes during birth. The true pelvis in both sexes has an inlet, an outlet, and a cavity: P-sacral promontory Pelvic inlet (pelvic brim): its boundaries are the sacral promontory A-symphysis/cubis posteriorly, the iliopectineal lines laterally, and the symphysis pubis L - ileopecineal lines anteriorly (Figs. 8.2 and 8.3; also see Fig. 8.1). Pelvic outlet: its boundaries are the coccyx posteriorly, the ischial anterior - public arch posterior - tip of the coccyx laterally - ischial tuberosity  3 wide notches : public arch lies anteriorly , bet. the ischiopubic rami sciatic notches lies laterally & divided into lesser & greater sciatic Foramina by the sacrotuberous & sacrospinous ligament tuberosities laterally, and the pubic arch anteriorly (see Figs. 8.1 to 8.3). The pelvic outlet has three wide notches. The pubic arch lies anteriorly, between the ischiopubic rami. The sciatic notches lie laterally and are divided into the greater and lesser sciatic foramina by the sacrotuberous and sacrospinous ligaments (see Figs. 8.1A and 8.2). From an obstetric standpoint, because the sacrotuberous ligaments are strong and relatively inflexible, they are considered to form part of the perimeter of the pelvic outlet. Thus, the outlet is diamond shaped, with the ischiopubic rami and the symphysis pubis forming the boundaries in front and the sacrotuberous ligaments and the coccyx forming the boundaries behind. Pelvic cavity: this short, curved canal, with a shallow anterior wall and a much deeper posterior wall, lies between the inlet and the outlet (see Fig. 8.2). lies bet the inleta the outlet -. posterior aspect of the pelvis : 2 openings in the the lesser · obsteric standpoint sacrotuberous , stronger & relatively inflexible separated from , 1) greater sciatic Foramina-larger & considered to form part of the sacrospinous ligament perimeter the aflet pehic by the of perineum the 2) lesser sciatic Foramina - provides communication bet the. of pelvis & gluteal region - lies inferiorly into the pelvic Floor pelvic cavity - short. curved canal wi shallow ant wall &. a much deeper posterior wall lies bet ,. Inlet & outlet Figure 8.2 Right half of the pelvis showing the pelvic inlet, pelvic outlet, and sacrotuberous and sacrospinous ligaments. Figure 8.3 Right hip bone. A. Medial surface. B. Lateral surface. Note the lines of fusion between the three bones—the ilium, the ischium, and the pubis. Pelvic Walls Bones and ligaments that are partly lined with muscles covered with fascia and parietal peritoneum form the walls of the pelvis. The pelvis has anterior, posterior, and lateral walls and an inferior wall or floor (Fig. 8.4). Figure 8.4 Right half of the pelvis showing the pelvic walls. Anterior Pelvic Wall The anterior pelvic wall is the shallowest wall and is formed by the bodies of the pubic bones, the pubic rami, and the symphysis pubis (Fig. 8.5). - shallowest wall Formed by the bodies of the public bones , public. & the symphysis pubis - rami Figure 8.5 Anterior wall of the pelvis (posterior view). Posterior Pelvic Wall The posterior pelvic wall is extensive and is formed by the sacrum and coccyx and by the piriformis muscles and their covering of parietal pelvic fascia (Figs. 8.6 and 8.7). - extensive & Formed by the sacrum & coccyx & by the piriformis muscle & covering of parietal pelvic Fascia Figure 8.6 Sacrum. A. Anterior view. B. Posterior view. Figure 8.7 Horizontal section through the pelvis showing the posterior wall of the pelvis. Sacrum The sacrum consists of five rudimentary vertebrae fused together to form a single wedge-shaped bone with an anterior concavity (see Figs. 8.2 and 8.6). The upper border or base of the bone articulates with the fifth lumbar vertebra. The narrow inferior border articulates with the coccyx. Laterally, the sacrum articulates with the two iliac bones to form the sacroiliac joints (see Fig. 8.1). The anterior and upper margins of the first sacral vertebra bulge forward to form the sacral promontory (see Fig. 8.2). This is the posterior margin of the pelvic inlet and is an important obstetric landmark used when measuring the size of the pelvis. base - articulateswl the 15  sacral hiatus - 15 & L4 Failed to meet in the midline & Forms , The sacral vertebral foramina together form the sacral canal. The laminae of the fifth sacral vertebra, and sometimes those of the fourth, fail to meet in the midline, forming the sacral hiatus (see Fig. 8.6). The sacral canal contains the anterior and posterior roots of the lumbar, sacral, and coccygeal spinal nerves; the filum terminale; and fibrofatty material. It also contains the lower part of the subarachnoid space down as far as the lower border of the second sacral vertebra (Fig. 8.8). Figure 8.8 Sacrum from behind. Laminae have been removed to show the sacral nerve roots lying within the sacral canal. Note that in the adult the spinal cord ends below, at the level of the lower border of the first lumbar vertebra. passage of the upper 4 sacral nerves The anterior and posterior surfaces of the sacrum possess four pairs of anterior and posterior sacral foramina, respectively, for the passage of the anterior and posterior rami of the upper four sacral nerves (see Fig. 8.6). The sacrum is usually wider in proportion to its length in the female than in the male. The sacrum is tilted forward so that it forms an angle with the fifth lumbar vertebra, called the lumbosacral angle. Coccyx - 4U -articulates at its base wh lower end of the samm The coccyx consists of four vertebrae fused together to form a small triangular bone, which articulates at its base with the lower end of the sacrum (see Fig. 8.6). The coccygeal vertebrae consist of bodies only, but the first vertebra possesses rudimentary transverse processes and cornua. The cornua are the remains of the pedicles and superior articular processes and project upward to articulate with the sacral cornua. Piriformis Muscle - arises from the Front of the sacrum & leaves the pelvis to enter the The piriformis muscle arises from the front of the sacrum and leaves the gluteal pelvis to enter the gluteal region by passing laterally through the greater region sciatic foramen (see Fig. 8.7). Full details of the piriformis are summarized in Table 8.1. Table 8.1 Pelvic Walls and Floor Muscles  P SP OF Fert OF For SP LA 4th sacral neve , pudendal newe C lower end o the 4th & 8th sach sacral nerve LPW Lateral Pelvic Wall - Formed by part of the hip bone below the pelvic inlet. OM , S SL. The lateral pelvic wall is formed by part of the hip bone below the pelvic inlet, the obturator membrane, the sacrotuberous and sacrospinous ligaments, and the obturator internus muscle and its covering fascia. S-ilium Hip Bone HB P& I-ischium In children, each hip bone (os coxae) consists of the ilium, which lies superiorly; the ischium, which lies posteriorly and inferiorly; and the pubis, A & I-pubis which lies anteriorly and inferiorly (see Fig. 8.3). A triradiate cartilage joins triradiate C. the three separate bones at the acetabulum. At puberty, these three bones - joins the 3 fuse together to form one large, irregular bone. The hip bones articulate with at separates bane the sacrum at the sacroiliac joints and form the anterolateral walls of the the acetabulum pelvis. They also articulate with one another anteriorly at the symphysis pubis. On the outer surface of the hip bone is a deep depression, the acetabulum, which articulates with the hemispherical head of the femur (see Figs. 8.1 and 8.3). Behind the acetabulum is a large notch, the greater sciatic notch, which is separated from the lesser sciatic notch by the spine of the ischium. The sciatic notches are converted into the greater and lesser sciatic foramina by the sacrotuberous and sacrospinous ligaments (see Fig. 8.2). The ilium, which is the upper flattened part of the hip bone, possesses the iliac crest (see Fig. 8.3). The iliac crest runs between the anterior and posterior superior iliac spines. Below these spines are the corresponding anterior and posterior inferior iliac spines. On the inner surface of the ilium-upper Flattened part of the hip bone possesses the , ilas crest acetabulum - articulates w hemispherical head of the femur  ilium is the large auricular surface for articulation with the sacrum. The iliopectineal line runs downward and forward around the inner surface of the ilium and serves to divide the false from the true pelvis. The ischium is the inferior and posterior part of the hip bone and possesses an ischial spine and an ischial tuberosity. The pubis is the anterior part of the hip bone and has a body and superior and inferior pubic rami. The body of the pubis bears the pubic crest and the pubic tubercle and articulates with the pubic bone of the opposite side at the symphysis pubis (see Fig. 8.1). In the lower part of the hip bone is a large opening, the obturator foramen, which is bounded by the parts of the ischium and pubis. The obturator membrane fills in most of the obturator foramen (see Fig. 8.3). OM Obturator Membrane Fibrous - sheet that almost completely closes the obturator foramen The obturator membrane is a fibrous sheet that almost completely closes the obturator foramen, leaving a small gap, the obturator canal, for the passage of the obturator nerve and vessels as they leave the pelvis to enter the thigh (see Fig. 8.3). obturator canal- passage of the obturator nerve& vessels SL Sacrotuberous Ligament The sacrotuberous ligament is strong and extends from the lateral part of the sacrum and coccyx and the posterior inferior iliac spine to the ischial tuberosity (Figs. 8.9 and 8.10; also see Figs. 8.2 and 8.7). strong & extendsFrom the lateral part of the samm & coccyx - Figure 8.9 A. Horizontal section through the pelvis showing the sacroiliac joints and the symphysis pubis. B. Sagittal section through the L5 vertebra and the sacrum showing the function of the sacrotuberous and sacrospinous ligaments in resisting the rotation force exerted on the sacrum by the weight of the trunk.  Figure 8.10 Lateral wall of the pelvis. SL Sacrospinous Ligament -strong & triangle shaped The sacrospinous ligament is strong and triangle shaped. It is attached by its base to the lateral part of the sacrum and coccyx and by its apex to the spine of the ischium (Figs. 8.2, 8.7, 8.9, and 8.10). The sacrotuberous and sacrospinous ligaments prevent the lower end of the sacrum and the coccyx from being rotated upward at the sacroiliac joint by the weight of the body (see Fig. 8.9B). The two ligaments also convert the greater and lesser sciatic notches into the greater and lesser sciatic foramina. Of M Obturator Internus Muscle - arises From the pelvic surface of the obturator foramen & membrane -  The obturator internus muscle arises from the pelvic surface of the obturator foramen and membrane (see Fig. 8.10). The muscle fibers converge to a tendon, which leaves the pelvis through the lesser sciatic foramen and inserts into the greater trochanter of the femur. Full details of the obturator internus are summarized in Table 8.1. TPW Inferior Pelvic Wall or Pelvic Floor The floor of the pelvis supports the pelvic viscera and is formed by the pelvic diaphragm and associated fascia. The pelvic floor stretches across the pelvis and divides it into the main pelvic cavity above, which contains the pelvic viscera, and the perineum below. The perineum is considered in detail in Chapter 10. PD Pelvic Diaphragm The paired levator ani and coccygeus muscles and their covering fasciae form the pelvic diaphragm (Fig. 8.11). It is incomplete anteriorly to allow passage of the urethra in males and the urethra and the vagina in females. General details of both muscle components are summarized in Table 8.1. - the paired levator ani & coccygeus muscle & their covering Fascine Form the pelvic diaphragm in incomplete anteriorly to allow passage of the urethra & Vagina - Females  Figure 8.11 Inferior wall (floor) of the pelvis. LAM Levator Ani Muscle The levator ani muscle is a wide, thin sheet forming the larger, more anterior part of the pelvic diaphragm. It has a linear origin from the back of the body of the pubis, a tendinous arch formed by a thickening of the fascia covering the obturator internus, and the spine of the ischium (see Fig. 8.11). From this extensive origin, groups of fibers sweep downward and medially to their insertion (Fig. 8.12) as follows: -wide , thin sheet forming the larger , more anterior part of the pelvic diaphragm tendinous arch-formed by a thickening of the Fascia covering the obturator internus & spine of the ischium , Figure 8.12 Levator ani muscle and coccygeus muscle seen on their inferior aspects. Note that the levator ani is made up of several different muscle groups. The levator ani and coccygeus muscles with their fascial coverings form a continuous muscular floor to the pelvis, known as the pelvic diaphragm. 1. Anterior fibers: the levator prostatae or sphincter vaginae form a sling around the prostate gland or vagina and insert into a mass of fibrous tissue, called the perineal body, in front of the anal canal. The levator prostatae support the prostate and stabilize the perineal body. AF : levator prostatue or sphincter vaginal Form asling around the prostate gland & insert into a mass Fibrous tissue called perineal body of IF : the puborectalis forms a sling around the junction of the rectum & anal canal PF ileo coccygens inserts into the : anoccocygeal body & the LoccyX. The sphincter vaginae constrict the vagina and stabilize the perineal body. 2. Intermediate fibers: the puborectalis forms a sling around the junction of the rectum and anal canal. The pubococcygeus passes posteriorly to insert into a small fibrous mass, called the anococcygeal body, between the tip of the coccyx and the anal canal. 3. Posterior fibers: the iliococcygeus inserts into the anococcygeal body and the coccyx. Action The levator ani muscles of the two sides form an efficient muscular sling that supports and maintains the pelvic viscera in position. They resist the rise in intrapelvic pressure during the straining and expulsive efforts of the abdominal muscles (as occurs in coughing). They also have an important sphincter action on the anorectal junction, and, in the female, they serve also as a sphincter of the vagina. Coccygeus Muscle Forms the smaller more posterior portion of the pelvicaphragm - , This triangular muscle forms the smaller, more posterior portion of the pelvic diaphragm (see Figs. 8.11 and 8.12). Pelvic Joints The four major joints in the adult pelvis include paired sacroiliac joints, the symphysis pubis, and the sacrococcygeal joint. Additional joints occur in the immature pelvis (e.g., between the ilium, ischium, and pubis elements of the os coxae; between the sacral vertebrae in the sacrum). The vertebral joints are discussed in Chapter 2, and the joints within the hip bone are reviewed in Chapter 11. Sacroiliac Joints The sacroiliac joints are strong synovial joints and are formed between the auricular surfaces of the sacrum and the iliac bones (see Fig. 8.9). The sacrum carries the weight of the trunk, and, apart from the interlocking of the irregular articular surfaces, the shape of the bones contributes little to the stability of the joints. The strong posterior and interosseous sacroiliac ligaments suspend the sacrum between the two iliac bones. The anterior sacroiliac ligament is thin and lies in front of the joint. The weight of the trunk tends to thrust the upper end of the sacrum downward and rotate the lower end of the bone upward (see Fig. 8.9B). The strong sacrotuberous and sacrospinous ligaments prevent this rotatory movement. The iliolumbar ligament connects the tip of the fifth lumbar transverse process to the iliac crest. Movements - small but limited amount of movement A small but limited amount of movement is possible at the sacroiliac joints. In older people, the synovial cavity disappears and the joint becomes fibrosed. Their primary function is to transmit the weight of the body from the vertebral column to the bony pelvis. Nerve Supply - sacral spinal nerves The nerve supply is from branches of the sacral spinal nerves. Symphysis Pubis The symphysis pubis is a cartilaginous joint between the two pubic bones (see Fig. 8.9). The articular surfaces are covered by a layer of hyaline cartilage and are connected together by a fibrocartilaginous disc. Ligaments that extend from one pubic bone to the other surround the joint. Movements Almost no movement is possible at this joint. Sacrococcygeal Joint The sacrococcygeal joint is a cartilaginous joint between the bodies of the last sacral vertebra and the first coccygeal vertebra. Ligaments join the cornua of the sacrum and coccyx. Movements - extensive flexion & extension are possible Extensive flexion and extension are possible at this joint.  Clinical Notes Joint Changes with Pregnancy During pregnancy, the symphysis pubis and the ligaments of the sacroiliac and sacrococcygeal joints undergo softening in response to hormones, thus increasing their mobility and increasing the potential size of the pelvis during childbirth. The hormones responsible are estrogen and progesterone produced by the ovary and the placenta. An additional hormone, called relaxin, produced by these organs can also have a relaxing effect on the pelvic ligaments. Joint Changes with Age Obliteration of the cavity in the sacroiliac joint occurs in both sexes after middle age. Sacroiliac Joint Disease The sacroiliac joint is innervated by the lower lumbar and sacral nerves so that disease in the joint can produce low back pain and pain referred along the sciatic nerve (sciatica). The sacroiliac joint is inaccessible to clinical examination. However, the joint comes closest to the surface at a small area located just medial to and below the posterior superior iliac spine. In disease of the lumbosacral region, movements of the vertebral column in any direction cause pain in the lumbosacral part of the column. In sacroiliac disease, pain is extreme on rotation of the vertebral column and is worst at the end of flexion. The latter movement causes pain because the hamstring muscles hold the hip bones in position, while the sacrum is rotating forward as the vertebral column is flexed. Biologic Sex Differences Anatomic differences related to biologic sex are easily recognized in the bony pelvis. The more obvious differences result from the adaptation of the female pelvis for childbearing. The stronger muscles in the male are responsible for the thicker bones and more prominent bony markings (Fig. 8.13; also see Fig. 8.1): False pelvis-male-deep Female - shallow pelvic inlef- male-heart Female-oral pelvic outlet - Female larger than male Figure 8.13 A. Pelvic inlet, pelvic outlet, diagonal conjugate, and axis of the pelvis. B. Some of the main differences between the female and the male pelvis. The false pelvis is shallow in the female and deep in the male. The pelvic inlet is transversely oval in the female but heart shaped in the male because of the indentation produced by the promontory of the sacrum in the male. The pelvic cavity is roomier in the female than in the male, and the distance between the inlet and the outlet is much shorter. The pelvic outlet is larger in the female than in the male. The ischial spines are everted in the female but inverted in the male. The sacrum is shorter, wider, and flatter in the female than in the male. shorter wider & , , Flatter sacrum in the Female  public arch : rounded & wider inRemale The subpubic angle, or pubic arch, is more rounded and wider in the female than in the male. Clinical Notes Clinical Concept: Pelvis Is a Basin with Holes in Its Walls Bones and ligaments form much of the walls of the pelvis; these are partly lined with muscles (obturator internus and piriformis) covered with fascia and parietal peritoneum. The attachments of the gluteal muscles and the obturator externus muscle are on the outside of the pelvis. Thus, the greater part of the bony pelvis is sandwiched between inner and outer muscles. The basin has anterior, posterior, and lateral walls and an inferior wall (floor) formed by the levator ani and coccygeus muscles and their covering fascia. The basin has several holes. The posterior wall has holes on the anterior surface of the sacrum, the anterior sacral foramina, for the passage of the anterior rami of the sacral spinal nerves. The sacrotuberous and sacrospinous ligaments convert the greater and lesser sciatic notches into the greater and lesser sciatic foramina. The greater sciatic foramen provides an exit from the true pelvis into the gluteal region for the sciatic nerve, the pudendal nerve, and the gluteal nerves and vessels. The lesser sciatic foramen provides an entrance into the perineum from the gluteal region for the pudendal nerve and the internal pudendal vessels. The lateral pelvic wall has a large hole, the obturator foramen, which is closed by the obturator membrane, except for a small opening that permits the obturator nerve to leave the pelvis and enter the thigh. Pelvic Measurements in Obstetrics The capacity and shape of the female pelvis are of fundamental importance in obstetrics. The female pelvis is well adapted for the process of childbirth. The pelvis is shallower and the bones are smoother than in the male. The size of the pelvic inlet is similar in the two sexes, but in the female, the cavity is larger and cylindrical, and the pelvic outlet is wider in both the anteroposterior and the transverse diameters. Four terms relating to areas of the pelvis are commonly used in clinical practice: The pelvic inlet (pelvic brim) (see Fig. 8.13) is bounded anteriorly by the symphysis pubis, laterally by the iliopectineal lines, and posteriorly by the sacral promontory. The pelvic outlet of the true pelvis (see Fig. 8.13) is bounded in front by the pubic arch, laterally by the ischial tuberosities, and posteriorly by the coccyx. The sacrotuberous ligaments also form part of the margin of the outlet. The pelvic cavity is the space between the inlet and the outlet (see Fig. 8.13). The axis of the pelvis is an imaginary line joining the central points of the anteroposterior diameters from the inlet to the outlet and is the curved course taken by the baby’s head as it descends through the pelvis during childbirth (Fig. 8.14A; also see Fig. 8.13). Internal Pelvic Assessments Internal pelvic assessments are made by vaginal examination during the later weeks of pregnancy, when the pelvic tissues are softer and more yielding than in the newly pregnant condition. Needless to say, considerable clinical experience is required to be able to assess the shape and size of the pelvis by vaginal examination: Pubic arch: spread the fingers under the pubic arch and examine its shape. Is it broad or angular? The examiner’s four fingers should be able to rest comfortably in the angle below the symphysis. Lateral walls: palpate the lateral walls, and determine whether they are concave, straight, or converging. Note the prominence of the ischial spines and the position of the sacrospinous ligaments. Posterior wall: the sacrum is palpated to determine whether it is straight or well curved. Finally, if the patient has relaxed the perineum  sufficiently, an attempt is made to palpate the promontory of the sacrum. The second finger of the examining hand is placed on the promontory, and the index finger of the free hand, outside the vagina, is placed at the point on the examining hand where it makes contact with the lower border of the symphysis. The fingers are then withdrawn and the distance measured (see Fig. 8.14B), providing the measurement of the diagonal conjugate, which is normally about 5 in. (13 cm). The anteroposterior diameter from the sacrococcygeal joint to the lower border of the symphysis is then estimated. Ischial tuberosities: the distance between the ischial tuberosities may be estimated by using the closed fist (see Fig. 8.14D). It measures about 4 in. (10 cm), but it is difficult to measure exactly. Female Pelvis dystocia deformities - of the petris Deformities of the pelvis may be responsible for dystocia (difficult labor). A contracted pelvis may obstruct the normal passage of the fetus. It may be indirectly responsible for dystocia by causing conditions such as malpresentation or malposition of the fetus, premature rupture of the fetal membranes, and uterine inertia. The cause of pelvic deformities may be congenital (rare) or acquired from disease, poor posture, or fractures caused by injury. Pelvic deformities are more common in women who have grown up in a poor environment and are undernourished. These women may have suffered from minor degrees of rickets in their youth. The pelvis can be classified into four general morphological groups: gynecoid, android, anthropoid, and platypelloid (see Fig. 8.14C). The gynecoid type, present in about 41% of women, is the typical female pelvis, which was previously described. The android type, present in about 33% of White females and 16% of Black females, is the male or funnel-shaped pelvis with a contracted outlet. The anthropoid type, present in about 24% of White females and 41% of Black females, is long, narrow, and oval shaped. The platypelloid type, present in only about 2% of women, is a wide pelvis flattened at the brim, with the promontory of the sacrum pushed forward. 1) gynecoid Present in11 % in women : 14 morphological groups) iarchoid: 310t A whiteFemale &l Mo black temas t warw wal snap a) platypelloid 2% : of women , wide pelvis flattened brim  Figure 8.14 A. Birth canal. Interrupted line indicates the axis of the canal. B. Procedure used in measuring the diagonal conjugate. C. Different types of pelvic inlets, according to Caldwell and Moloy. D. Estimation of the width of the pelvic outlet by means of a closed fist. DF PELVIC FASCIA ~ Formed of connective tissue The pelvic fascia is formed of connective tissue and is continuous above with the fascia lining the abdominal walls. Below, the fascia is continuous with the fascia of the perineum. The pelvic fascia can be divided into parietal and visceral layers. PPF Parietal Pelvic Fascia The parietal pelvic fascia lines the walls of the pelvis and is named according to the muscle it overlies (Fig. 8.15). Where the pelvic diaphragm is deficient anteriorly, the parietal pelvic fascia becomes continuous through the opening with the fascia covering the inferior surface of the pelvic diaphragm. In the perineum, it covers the perineal membrane and forms the fascia deep to that structure. Figure 8.15 Coronal section through the posterior aspect of the pelvis. Visceral Pelvic Fascia The visceral layer of pelvic fascia covers and supports all the pelvic viscera. In certain locations, the fascia thickens and extends from the viscus to the - thickens & extends viscus to the pelvic walls & provides support  pelvic walls and provides added support. These fascial condensations are termed ligaments and are named according to their attachments (e.g., the pubovesical and the sacrocervical ligaments). Clinical Notes Cervical Fascial Ligaments In the female, the fascial ligaments attached to the uterine cervix are of particular clinical importance because they assist with the support of the uterus and thus prevent uterine prolapse (see Chapter 9). The visceral pelvic fascia around the uterine cervix and vagina is commonly referred to as the parametrium. PP PELVIC PERITONEUM The parietal peritoneum lines the pelvic walls and is reflected onto the pelvic viscera; it becomes continuous with the visceral peritoneum (see Fig. 8.15). Further details are provided in Chapter 9. Clinical Notes False Pelvis Fracture Fractures of the false pelvis caused by direct trauma occasionally occur. The upper part of the ilium is seldom displaced because of the attachment of the iliacus muscle on the inside and the gluteal muscles on the outside. True Pelvis Fracture The mechanism of fractures of the true pelvis can be better understood if the pelvis is regarded not only as a basin but also as a rigid ring (Fig. 8.16). The ring is made up of the pubic rami, the ischium, the acetabulum, the ilium, and the sacrum, joined by strong ligaments at the sacroiliac and symphyseal joints. If the ring breaks at any one point, the fracture will be stable and no displacement will occur. However, if two breaks occur in the ring, the fracture will be unstable and displacement will occur, because the postvertebral and abdominal muscles will shorten and elevate the lateral part of the pelvis (see Fig. 8.16). The break in the ring may occur not as the result of a fracture but as the result of disruption of the sacroiliac or symphyseal joints. Fracture of the bone on either side of the joint is more common than disruption of the joint. The forces responsible for the disruption of the bony ring may be anteroposterior compression, lateral compression, or shearing. Trauma to the true pelvis can result in fracture of the lateral mass of the sacrum. A heavy fall on the greater trochanter of the femur may drive the head of the femur through the floor of the acetabulum into the pelvic cavity. Sacrococcygeal Fractures Fractures of the lateral mass of the sacrum may occur as part of a pelvic fracture. Fractures of the coccyx are rare. However, coccydynia (coccygeal pain) is common and is usually caused by direct trauma to the coccyx, as in falling down a flight of stairs. The anterior surface of the coccyx can be palpated in a rectal examination. Minor Pelvic Fractures The anterior superior iliac spine may be pulled off by the forcible contraction of the sartorius muscle in athletes (see Fig. 8.16D). In a similar manner, the anterior inferior iliac spine may be avulsed by the contraction of the rectus femoris muscle. The ischial tuberosity can be avulsed by the contraction of the hamstring muscles. Healing may occur by fibrous union, possibly resulting in elongation of the muscle unit and some reduction in muscular efficiency. Anatomy of Complications Fractures of the true pelvis are commonly associated with injuries to the soft pelvic tissues. If damaged, the thin pelvic veins—namely, the internal iliac veins and their tributaries—that lie in the parietal pelvic fascia beneath the parietal peritoneum can be the source of a massive hemorrhage, which may be life threatening. The male urethra is often damaged, especially in vertical shear fractures that may disrupt the urogenital diaphragm (see Chapter 10). The urinary bladder, which lies immediately behind the pubis in both sexes, is occasionally damaged by spicules of the bone. A full bladder is more likely to be injured than an empty bladder (see Chapter 9). The rectum lies within the concavity of the sacrum and is protected and rarely damaged. However, fractures of the sacrum or ischial spine may be thrust into the pelvic cavity, tearing the rectum. Nerve injuries can follow sacral fractures. The laying down of fibrous tissue around the anterior or posterior nerve roots or the branches of the sacral spinal nerves can result in persistent pain. Damage to the sciatic nerve may occur in fractures involving the boundaries of the greater sciatic notch. The fibular (peroneal) part of the sciatic nerve is most often involved, resulting in the inability of a conscious patient to dorsiflex the ankle joint or failure of an unconscious patient to reflexly plantarflex (ankle jerk) the foot (see Chapter 11). Pelvic Floor The pelvic diaphragm is a gutter-shaped sheet of muscle formed by the levator ani and coccygeus muscles and their covering fasciae. The muscle fibers on the two sides slope downward and backward from their origins to the midline, producing a gutter that slopes downward and forward. A rise in the intra-abdominal pressure, caused by the contraction of the diaphragm and the muscles of the anterior and lateral abdominal walls, is counteracted by the contraction of the muscles forming the pelvic floor. By this means, the pelvic viscera are supported and do not “drop out” through the pelvic outlet. Contraction of the puborectalis fibers greatly assists the anal sphincters in maintaining continence under these conditions by pulling the anorectal junction upward and forward. However, during the act of defecation, the levator ani continues to support the pelvic viscera, but the puborectalis fibers relax with the anal sphincters. Female Pelvic Floor Functional Significance The female pelvic floor serves an important function during the second stage of labor (Fig. 8.17). At the pelvic inlet, the widest diameter is transverse so that the longest axis of the baby’s head (anteroposterior) takes up the transverse position. When the head reaches the pelvic floor, the gutter shape of the floor tends to cause the baby’s head to rotate so that its long axis comes to lie in the anteroposterior position. The occipital part of the head now moves downward and forward along the gutter until it lies under the pubic arch. As the baby’s head passes through the lower part of the birth canal, the small gap that exists in the anterior part of the pelvic diaphragm becomes enormously enlarged so that the head may slip through into the perineum. Once the baby has passed through the perineum, the levator ani muscles recoil and take up their previous position. Pelvic Floor Injury Injury to the pelvic floor during a difficult childbirth can result in the loss of support for the pelvic viscera leading to uterine and vaginal prolapse, herniation of the bladder (cystocele), and alteration in the position of the bladder neck and urethra, leading to stress incontinence. In the latter condition, the patient dribbles urine whenever the intra-abdominal pressure is raised, as in coughing. Prolapse of the rectum may also occur. Partial Fusion of Sacral Vertebrae The first sacral vertebra can be partly or completely separated from the second sacral vertebra. Occasionally, on radiographs of the vertebral column, examples are seen in which the fifth lumbar vertebra has fused with the first sacral vertebra (see Chapter 2). Figure 8.16 A–C. Different types of fractures of the pelvic basin. D. Avulsion fractures of the pelvis. The sartorius muscle is responsible for the avulsion of the anterior superior iliac spine; the straight head of the rectus femoris muscle, for the avulsion of the anterior inferior iliac spine; and the hamstring muscles, for the avulsion of the ischial tuberosity. Figure 8.17 Stages in rotation of the baby’s head during the second stage of labor. The shape of the pelvic floor plays an important part in this process. - derived from the lumbar & sacral plexuses PELVIC NERVES supplies - the pelis & perineum & lower abdomen & lower limb Nerves derived from the lumbar and sacral plexuses and the sympathetic chain form extensive networks across the pelvic walls. These branches supply the pelvis and perineum and also the lower abdomen and the lower limb. Lumbar Plexus The lumbar plexus lies in the posterior abdominal wall (see Chapter 7). Two branches, the lumbosacral trunk and the obturator nerve, have notable relations to the pelvic walls. Lumbosacral Trunk Part of the anterior ramus of the fourth lumbar nerve emerges from the medial border of the psoas muscle and joins the anterior ramus of the fifth lumbar nerve to form the lumbosacral trunk (Figs. 8.18 and 8.19). This trunk enters the pelvis by passing down in front of the sacroiliac joint and joins the sacral plexus. Figure 8.18 Posterior pelvic wall showing the sacral plexus, superior hypogastric plexus, and right and left inferior hypogastric plexuses. Pelvic parts of the sympathetic trunks are also shown. Figure 8.19 Sacral plexus. Obturator Nerve The obturator nerve is a branch of the lumbar plexus (L2, 3, and 4). It emerges from the medial border of the psoas muscle in the abdomen and accompanies the lumbosacral trunk down into the pelvis (see Fig. 8.18). It crosses the front of the sacroiliac joint and runs forward on the lateral pelvic wall in the angle between the internal and external iliac vessels (see Fig. 8.10). On reaching the obturator canal (i.e., the upper part of the obturator foramen, which is devoid of the obturator membrane), it splits into anterior and posterior divisions that pass through the canal to enter the adductor region of the thigh. The distribution of the obturator nerve in the thigh is considered in Chapter 11. Pelvic Branches Sensory branches supply the parietal peritoneum on the lateral wall of the pelvis. Sacral Plexus The sacral plexus lies on the posterior pelvic wall in front of the piriformis muscle (see Fig. 8.18). It is formed from the lumbosacral trunk (see above) and the anterior rami of the first, second, third, and fourth sacral nerves (see Fig. 8.19). The lumbosacral trunk passes down into the pelvis and joins the sacral nerves as they emerge from the anterior sacral foramina. Relations Anteriorly: the internal iliac vessels and their branches and the rectum (see Fig. 8.10) Posteriorly: the piriformis muscle (see Fig. 8.18) Branches The branches of the sacral plexus and their distribution are summarized in Table 8.2. Table 8.2 Sacral Plexus Branches and Distribution  SGN IGN NTP NTOF NTQF DON PONOTT SN CFP PN Branches to the lower limb that leave the pelvis through the greater sciatic foramen (see Fig. 8.10): 1. Sciatic nerve (L4 and 5; S1, 2, and 3) is the largest branch of the plexus and the largest nerve in the body (see Figs. 8.7 and 8.19).2. Superior gluteal nerve supplies the gluteus medius and minimus and the tensor fasciae latae muscles.3. Inferior gluteal nerve supplies the gluteus maximus muscle.4. Nerve to the quadratus femoris muscle also supplies the inferior gemellus muscle.5. Nerve to the obturator internus muscle also supplies the superior gemellus muscle.6. Posterior cutaneous nerve of the thigh supplies the skin of the buttock and the back of the thigh. Branches to the pelvic muscles, pelvic viscera, and perineum (see Figs. 8.18 and 8.19): 1. Pudendal nerve (S2, 3, and 4) leaves the pelvis through the greater sciatic foramen and enters the perineum through the lesser sciatic foramen (see Fig. 8.10).2. Nerve to the piriformis muscle is a small branch to only this muscle.3. Pelvic splanchnic nerves constitute the sacral part of the parasympathetic system and arise from the second, third, and fourth sacral nerves. They are distributed mainly to the pelvic viscera.  Perforating cutaneous nerve supplies the skin of the lower medial part of the buttock. supplies the skin of the lower medial part of the buttock Clinical Notes Nerve Pressure from Fetal Head During the later stages of pregnancy, when the fetal head has descended into the pelvis, the mother often complains of discomfort or aching pain extending down one of the lower limbs. The discomfort, caused by pressure from the fetal head, is often relieved by changing position, such as lying on the side in bed. Nerve Invasion by Malignant Tumors Malignant tumors extending from neighboring viscera can invade the sacral plexus or its branches. A carcinoma of the rectum, for example, can cause severe intractable pain down the lower limbs. Referred Pain from Obturator Nerve The obturator nerve lies on the lateral wall of the pelvis and supplies the parietal peritoneum. An inflamed appendix hanging down into the pelvic cavity could cause irritation of the obturator nerve endings, leading to referred pain down the inner side of the right thigh. Inflammation of the ovaries can produce similar symptoms. Caudal Anesthesia (Analgesia) Anesthetic solutions can be injected into the sacral canal through the sacral hiatus. The solutions then act on the spinal roots of the second, third, fourth and fifth sacral and coccygeal segments of the cord as they emerge from the dura mater. The roots of higher spinal segments can also be blocked by this method. The needle must be confined to the lower part of the sacral canal, because the meninges extend down as far as the lower border of the second sacral vertebra. Caudal anesthesia is used in obstetrics to block pain fibers from the cervix of the uterus and to anesthetize the perineum. Autonomic Nerves Sympathetic fibers derived from the sympathetic chain and parasympathetic fibers from the sacral nerves intertwine and form expansive plexuses on the pelvic walls and viscera. These autonomic fibers supply the pelvis and perineum and also the hindgut. Pelvic Part of Sympathetic Trunk The pelvic part of the sympathetic trunk is continuous above, behind the common iliac vessels, with the abdominal part (see Fig. 8.18). It runs down behind the rectum on the front of the sacrum, medial to the anterior sacral foramina. The sympathetic trunk has four or five segmentally arranged ganglia. Below, the two trunks converge and finally unite in front of the coccyx. Branches GRC to the S & CN Gray rami communicantes to the sacral and coccygeal nerves Fibers that join the hypogastric plexuses Pelvic Splanchnic Nerves The pelvic splanchnic nerves form the parasympathetic part of the autonomic nervous system in the pelvis. The preganglionic fibers arise from the second, third, and fourth sacral nerves and synapse in ganglia in the inferior hypogastric plexus or in the walls of the viscera. Some of the parasympathetic fibers ascend through the hypogastric plexuses and thence via the aortic plexus to the inferior mesenteric plexus. The fibers are then distributed along branches of the inferior mesenteric artery to supply the large bowel from the left colic flexure to the upper half of the anal canal. SHP Superior Hypogastric Plexus The superior hypogastric plexus is situated in front of the promontory of the sacrum (see Fig. 8.18). It forms as a continuation of the aortic plexus and from branches of the third and fourth lumbar sympathetic ganglia. It contains sympathetic and sacral parasympathetic nerve fibers and visceral afferent nerve fibers. The superior hypogastric plexus divides inferiorly to form the right and left hypogastric nerves. IHP Inferior Hypogastric Plexuses The inferior hypogastric plexuses lie on each side of the rectum, the base of the bladder, and the vagina (see Fig. 8.18). Each plexus is formed from a hypogastric nerve (from the superior hypogastric plexus) and from the pelvic splanchnic nerves. It contains postganglionic sympathetic fibers, preganglionic and postganglionic parasympathetic fibers, and visceral afferent fibers. Branches pass to the pelvic viscera via small subsidiary plexuses. PELVIC ARTERIES Several arteries stream across the pelvic walls. The common and external iliac arteries are related to the pelvic brim. The internal iliac, superior rectal, ovarian, and median sacral arteries run into the pelvic cavity. The arteries related to the pelvic walls are densely packed in the pelvic cavity and subject to significant variation in their branching patterns of origin. However, these vessels always terminate where they are supposed. Thus, identifying the individual arteries by their destinations is more reliable than by their origins. CIA Common Iliac Artery Each common iliac artery ends at the pelvic inlet in front of the sacroiliac joint by dividing into the external and internal iliac arteries (see Figs. 8.10 and 8.18). EIA External Iliac Artery artery Femoral antry · interior epigastric · deep circumflex line arteries the False pelvis by under the inquiral lig to become -leaves passing.  The external iliac artery runs along the medial border of the psoas muscle, following the pelvic brim (see Fig. 8.10), and gives off the inferior epigastric and deep circumflex iliac branches. It leaves the false pelvis by passing under the inguinal ligament to become the femoral artery. True Pelvis Arteries The following arteries enter the pelvic cavity: IIA Internal iliac artery SRA Superior rectal artery OA Ovarian artery MSA Median sacral artery IIA Internal Iliac Artery The internal iliac artery passes down into the pelvis to the upper margin of the greater sciatic foramen, where it divides into anterior and posterior divisions (see Fig. 8.10). The branches of these divisions supply the pelvic viscera, the perineum, the pelvic walls, and the buttocks. The origin of the terminal branches is subject to variation, but the usual arrangement is shown in Diagram 8.1. i Diagram 8.1 Branches of the Internal Iliac Artery. Anterior Division Branches  Umbilical artery: the superior vesical artery arises from the proximal patent part of the umbilical artery. It supplies the upper portion of the bladder (see Fig. 8.10). It also gives off the artery to the vas deferens. Obturator artery: this artery runs forward along the lateral wall of the pelvis with the obturator nerve and leaves the pelvis through the obturator canal. Inferior vesical artery: this artery supplies the base of the bladder and the prostate and seminal vesicles in the male. Middle rectal artery: commonly, this artery arises with the inferior vesical artery (see Fig. 8.10). It supplies the muscle of the lower rectum and anastomoses with the superior rectal and inferior rectal arteries. Internal pudendal artery: this artery leaves the pelvis through the greater sciatic foramen and enters the gluteal region below the piriformis muscle (see Fig. 8.10). It then curls around the ischial spine (with the pudendal nerve) and enters the perineum by passing through the lesser sciatic foramen. It passes forward in the pudendal canal with the pudendal nerve. Its branches supply the musculature of the anal canal and the skin and muscles of the perineum. Inferior gluteal artery: this artery leaves the pelvis through the greater sciatic foramen below the piriformis muscle (see Fig. 8.10). It passes between the first and second or second and third sacral nerves. Uterine artery: this artery runs medially on the floor of the pelvis and crosses the ureter superiorly (see Chapter 9). It passes above the lateral fornix of the vagina to reach the uterus. Here, it ascends between the layers of the broad ligament along the lateral margin of the uterus. It ends by following the uterine tube laterally, where it anastomoses with the ovarian artery. The uterine artery gives off a vaginal branch. Vaginal artery: this artery usually takes the place of the inferior vesical artery present in the male. It supplies the vagina and the base of the bladder. Posterior Division Branches Iliolumbar artery: this artery ascends across the pelvic inlet posterior to the external iliac vessels, psoas, and iliacus muscles. Lateral sacral arteries: these arteries descend in front of the sacral  plexus, giving off branches to neighboring structures and entering the anterior sacral foramina (see Fig. 8.10). Superior gluteal artery: this artery leaves the pelvis through the greater sciatic foramen above the piriformis muscle. It supplies the gluteal region. Superior Rectal Artery The superior rectal artery is a direct continuation of the inferior mesenteric artery. The name changes as the latter artery crosses the common iliac artery. It supplies the mucous membrane of the rectum and the upper half of the anal canal. Ovarian Artery The ovarian artery arises from the abdominal part of the aorta at the level of the first lumbar vertebra. The artery is long and slender and passes downward and laterally behind the peritoneum. It crosses the external iliac artery at the pelvic inlet and enters the suspensory ligament of the ovary. It then passes into the broad ligament and enters the ovary by way of the mesovarium. The testicular artery enters the inguinal canal and does not enter the pelvis. Median Sacral Artery The median sacral artery is a small artery that arises at the bifurcation of the aorta (see Fig. 8.18). It descends over the anterior surface of the sacrum and coccyx. The distribution of the visceral branches of the pelvic arteries is discussed in detail with the individual viscera in Chapter 9. PELVIC VEINS For the greater part, the pelvic veins correspond to the pelvic arteries. The external iliac vein begins behind the inguinal ligament as a continuation of the femoral vein. It runs along the medial side of the corresponding artery and joins the internal iliac vein to form the common iliac vein (see Fig. 8.10). It receives the inferior epigastric and deep circumflex iliac veins.  The internal iliac vein begins by the joining together of tributaries that correspond to the branches of the internal iliac artery. It passes upward in front of the sacroiliac joint and joins the external iliac vein to form the common iliac vein (see Fig. 8.10). The median sacral veins accompany the corresponding artery and end by joining the left common iliac vein. PELVIC LYMPHATICS The lymph nodes and vessels are arranged in a chain along the main blood vessels. The nodes are named after the blood vessels with which they are associated. Thus, there are external iliac nodes, internal iliac nodes, and common iliac nodes. SURFACE ANATOMY Several bony features of the pelvic walls are palpable in an adult of average body build. Additionally, significant parts of the underlying urogenital tracts are palpable with proper manipulation. Collectively, these form notable surface landmarks that help orient the clinician conducting a physical examination or procedure. Iliac Crest The iliac crest can be felt through the skin along its entire length (Figs. 8.20 to 8.22). Figure 8.20 Anterior view of a white male showing the surface anatomy of the pelvic and inguinal regions and the groin. (Modified from Moore KL, Dalley AF II, Agur AMR. Clinically Oriented Anatomy. 8th ed. Baltimore, MD: Wolters Kluwer, 2018: Fig. 6.61.) Figure 8.21 Anterior view of a white female showing the surface anatomy of the pelvic and inguinal regions and the groin. (Modified from Moore KL, Dalley AF II, Agur AMR. Clinically Oriented Anatomy. 8th ed. Baltimore, MD: Wolters Kluwer, 2018: Fig. 6.67.) Figure 8.22 Relationship between different parts of the pelvis and the body surface. The anterior superior iliac spine is situated at the anterior end of the iliac crest and lies at the upper lateral end of the fold of the groin (see Figs. 8.20 to 8.22). The posterior superior iliac spine is situated at the posterior end of the iliac crest (see Fig. 8.22). It lies at the bottom of a small skin dimple and on a level with the second sacral spine, which coincides with the lower limit of the subarachnoid space. It also coincides with the level of the middle of the sacroiliac joint. Pubic Tubercle and Crest The pubic tubercle can be felt on the upper border of the pubis (see Figs. 8.20 to 8.22). The medial end of the inguinal ligament is attached to it. The tubercle can be palpated easily in the male by invaginating the scrotum from below with the examining finger. In the female, the pubic tubercle can be palpated through the lateral margin of the labium majus. The pubic crest is the ridge of the bone on the superior surface of the pubic bone, medial to the pubic tubercle (see Figs. 8.1 and 8.22). Symphysis Pubis The symphysis pubis (see Figs. 8.1 and 8.22) lies in the midline between the bodies of the pubic bones and can be palpated as a solid structure through the fat that is present in this region. Sacrum and Coccyx The spinous processes of the sacrum (see Fig. 8.22) are fused with each other in the midline to form the median sacral crest. The crest can be felt beneath the skin in the uppermost part of the cleft between the buttocks. The sacral hiatus is situated on the posterior aspect of the lower end of the sacrum, where the extradural space terminates. The hiatus lies about 2 in. (5 cm) above the tip of the coccyx and beneath the skin of the cleft between the buttocks. The inferior surface and tip of the coccyx can be palpated in the cleft between the buttocks about 1 in. (2.5 cm) behind the anus. The anterior surface of the coccyx can be palpated with the gloved finger in the anal canal. Urinary Bladder In adults, the empty bladder is a pelvic organ and lies posterior to the symphysis pubis. As the bladder fills, it rises up out of the pelvis into the abdomen, where it can be palpated through the anterior abdominal wall above the symphysis pubis (Fig. 8.23A). The peritoneum covering the distended bladder becomes peeled off from the anterior abdominal wall so that the front of the bladder is in direct contact with the abdominal wall (see Chapter 9). Figure 8.23 A. Surface anatomy of the empty bladder and the full bladder. B. Height of the fundus of the uterus at various months of pregnancy. Note that the peritoneum covering the distended bladder becomes peeled off from the anterior abdominal wall so that the front of the bladder comes to lie in direct contact with the abdominal wall. In children, until the age of 6 years, the bladder is an abdominal organ even when empty because the capacity of the pelvic cavity is not great enough to contain it. The neck of the bladder lies just below the level of the upper border of the symphysis pubis. Uterus