Pelvis Osteology, Muscles & Important Structures - Lecture 12 PDF

Lecture 12- Pelvis Osteology, muscles and important structures and landmarks Dr. Rasem Mustafa PhD. Dr.med.dent (Anatomy and Cell Biology) Dr. Rasem Mustafa 1  GENERAL DESCRIPTION  The pelvis and perineum are interrelated regions associat...

Lecture 12- Pelvis Osteology, muscles and important structures and landmarks Dr. Rasem Mustafa PhD. Dr.med.dent (Anatomy and Cell Biology) Dr. Rasem Mustafa 1  GENERAL DESCRIPTION  The pelvis and perineum are interrelated regions associated with the pelvic bones and terminal parts of the vertebral column.  The pelvis - Is divided into two regions: The false pelvis (greater pelvis) is the superior region related to upper parts of the pelvic bones and lower lumbar vertebrae and is generally considered part of the abdominal cavity. The true pelvis (lesser pelvis) is related to the inferior parts of the pelvic bones, sacrum, and coccyx, and has an inlet and an outlet. Dr. Rasem Mustafa 2  The true pelvis (lesser pelvis)  Contains and supports the bladder, rectum, anal canal, and reproductive tracts  A cavity enclosed by the true pelvis called pelvic cavity The bowl-shaped cavity and Consists of the 1. Pelvic inlet 2. Walls 3. Floor. 4. Pelvic outlet This cavity is continuous superiorly with the abdominal cavity and contains elements of the urinary, gastrointestinal, and reproductive systems. Within the pelvic cavity, the bladder is positioned anteriorly and the rectum posteriorly in the midline. Dr. Rasem Mustafa 3 o As it fills, the bladder expands superiorly into the abdomen. o The urethra passes through the pelvic floor to the perineum, where, in women, it opens externally and in men it enters the base of the penis. o Continuous with the sigmoid colon at the level of vertebra SIII, the rectum terminates at the anal canal, which penetrates the pelvic floor to open into the perineum. o This flexure is maintained by muscles of the pelvic floor and is relaxed during defecation. A skeletal muscle sphincter is associated with the anal canal and the urethra as each passes through the pelvic floor. Dr. Rasem Mustafa 4  The pelvic cavity contains: most of the reproductive tract in women and part of the reproductive tract in men. In women, the vagina penetrates the pelvic floor and connects with the uterus in the pelvic cavity. The uterus is positioned between the rectum and the bladder. A uterine (fallopian) tube extends laterally on each side toward the pelvic wall to open near the ovary. In men, the pelvic cavity contains the site of connection between the urinary and reproductive tracts. It also contains major glands associated with the reproductive system—the prostate and two seminal vesicles. Dr. Rasem Mustafa 5  The pelvic cavity is lined by peritoneum continuous with the peritoneum of the abdominal cavity that drapes over the superior aspects of the pelvic viscera, but in most regions, does not reach the pelvic floor. The pelvic viscera are located in the midline of the pelvic cavity. The bladder is anterior and the rectum is posterior. In women, the uterus lies between the bladder and rectum. Other structures, such as vessels and nerves, lie deep to the peritoneum in association with the pelvic walls and on either side of the pelvic viscera. Dr. Rasem Mustafa 6 1. Pelvic inlet  The pelvic inlet is somewhat heart shaped and completely ringed by bone.  Posteriorly, the inlet is bordered by the body of vertebra SI, which projects into the inlet as the sacral promontory.  On each side of this vertebra, wing- like transverse processes called the alae (wings) contribute to the margin of the pelvic inlet.  Laterally, a prominent rim on the pelvic bone continues the boundary of the inlet forward to the pubic symphysis, where the two pelvic bones are joined in the midline. Dr. Rasem Mustafa 7  The promontory of the sacrum protrudes into the inlet, forming its posterior margin in the midline. On either side of the promontory, the margin is formed by the alae of the sacrum. The margin of the pelvic inlet then crosses the sacro-iliac joint and continues along the linea terminalis (i.e., the arcuate line, the pecten pubis or pectineal line, and the pubic crest) to the pubic symphysis. Structures pass between the pelvic cavity and the abdomen through the pelvic inlet. During childbirth, the fetus passes through the pelvic inlet from the abdomen, into which the uterus has expanded during pregnancy, and then passes through the pelvic outlet. Dr. Rasem Mustafa 8 2. Pelvic walls The walls of the true pelvis consist predominantly of bone, muscle, and ligaments, with the sacrum, coccyx, and inferior half of the pelvic bones forming much of them. Two ligaments— the sacrospinous and the sacrotuberous ligaments—are important architectural elements of the walls because they link each pelvic bone to the sacrum and coccyx. These ligaments also convert two notches on the pelvic bones—the greater and lesser sciatic notches—into foramina on the lateral pelvic walls. The smaller of the two, the sacrospinous ligament, is triangular, with its apex attached to the ischial spine and its base attached to the related margins of the sacrum and the coccyx. Dr. Rasem Mustafa 9  The sacrotuberous ligament is also triangular and is superficial to the sacrospinous ligament. Its base has a broad attachment that extends from the posterior superior iliac spine of the pelvic bone, along the dorsal aspect and the lateral margin of the sacrum, and onto the dorsolateral surface of the coccyx. Laterally, the apexof the ligament is attached to the medial margin of the ischial tuberosity. Completing the walls are the obturator internus and piriformis muscles, which arise in the pelvis and exit through the sciatic foramina to act on the hip joint. Dr. Rasem Mustafa 10 3. Pelvic outlet The diamond-shaped pelvic outlet Is formed by both bone and ligaments. It is limited anteriorly in the midline by the pubic symphysis. On each side, the inferior margin of the pelvic bone projects posteriorly and laterally from the pubic symphysis to end in a prominent tuberosity, the ischial tuberosity. Together, these elements construct the pubic arch, which forms the margin of the anterior half of the pelvic outlet. The sacrotuberous ligament continues this margin posteriorly from the ischial tuberosity to the coccyx and sacrum. The pubic symphysis, ischial tuberosities, and coccyx can all be palpated. Dr. Rasem Mustafa 11 4. Pelvic floor The pelvic floor, which separates the pelvic cavity from the perineum, is formed by muscles and fascia. Two levator ani muscles attach peripherally to the pelvic walls and join each other at the midline by a connective tissue raphe. Together they are the largest components of the bowl- or funnel-shaped structure known as the pelvic diaphragm, which is completed posteriorly by the coccygeus muscles. These latter muscles overlie the sacrospinous ligaments and pass between the margins of the sacrum and the coccyx and a prominent spine on the pelvic bone, the ischial spine. Dr. Rasem Mustafa 12  The pelvic diaphragm forms most of the pelvic floor and in its anterior regions contains a U-shaped defect, which is associated with elements of the urogenital system. * The anal canal passes from the pelvis to the perineum through a posterior circular orifice in the pelvic diaphragm. The pelvic floor is supported anteriorly by: the perineal membrane, and muscles in the deep perineal pouch. Dr. Rasem Mustafa 13  The perineal membrane is a thick, triangular fascial sheet that fills the space between the arms of the pubic arch, and has a free posterior border. The deep perineal pouch is a narrow region superior to the perineal membrane. The margins of the U-shaped defect in the pelvic diaphragm merge into the walls of the associated viscera and with muscles in the deep perineal pouch below. The vagina and the urethra penetrate the pelvic floor to pass from the pelvic cavity to the perineum. Dr. Rasem Mustafa 14  Perineum The perineum is inferior to the floor of the pelvic cavity; its boundaries form the pelvic outlet. The perineum contains the external genitalia and external openings of the genitourinary and gastrointestinal systems. The perineum lies inferior to the pelvic floor between the lower limbs. Its margin is formed by the pelvic outlet. An imaginary line between the ischial tuberosities divides the perineum into two triangular regions. Anteriorly, the urogenital triangle contains the roots of the external genitalia and, in women, the openings of the urethra and the vagina. In men, the distal part of the urethra is enclosed by erectile tissues and opens at the end of the penis. Posteriorly, the anal triangle contains the anal aperture. Dr. Rasem Mustafa 15  Pelvic Bones  The bones of the pelvis consist of :  The right and left pelvic (hip) bones  Sacrum  Coccyx.  The sacrum articulates superiorly with vertebra LV at the lumbosacral joint. The pelvic bones articulate posteriorly with the sacrum at the sacro-iliac joints and with each other anteriorly at the pubic symphysis. Dr. Rasem Mustafa 16  The right and left pelvic (hip) bones  Is irregular in shape and has two major parts separated by an oblique line on the medial surface of the bone: The pelvic bone above this line represents the lateral wall of the false pelvis, which is part of the abdominal cavity. The pelvic bone below this line represents the lateral wall of the true pelvis, which contains the pelvic cavity. The linea terminalis is the lower two- thirds of this line and contributes to the margin of the pelvic inlet. Dr. Rasem Mustafa 17  The lateral surface of the pelvic bone has a large articular socket, the acetabulum, which, together with the head of the femur, forms the hip joint.  Inferior to the acetabulum is the large obturator foramen, most of which is closed by a flat connective tissue membrane, the obturator membrane. A small obturator canal remains open superiorly between the membrane and adjacent bone, providing a route of communication between the lower limb and the pelvic cavity. Dr. Rasem Mustafa 18  The posterior margin of the bone is marked by two notches separated by the ischial spine: the greater sciatic notch, and the lesser sciatic notch. The posterior margin terminates inferiorly as the large ischial tuberosity.  The irregular anterior margin of the pelvic bone is marked by the anterior superior iliac spine, the anterior inferior iliac spine, and the pubic tubercle. Dr. Rasem Mustafa 19  Components of the pelvic bone Each pelvic bone is formed by three elements: o Ilium o Pubis o Ischium. At birth, these bones are connected by cartilage in the area of the acetabulum; later, at between 16 and 18 years of age, they fuse into a single bone Dr. Rasem Mustafa 20  o Ilium  The ilium is the most superior in position.  The ilium is separated into upper and lower parts by a ridge on the medial surface: Posteriorly, the ridge is sharp and lies immediately superior to the surface of the bone that articulates with the sacrum. This sacral surface has a large L-shaped facet for articulating with the sacrum and an expanded, posterior roughened area for the attachment of the strong ligaments that support the sacro-iliac joint. Anteriorly, the ridge separating the upper and lower parts of the ilium is Dr. Rasem Mustafa 21 rounded and termed the arcuate line.  The arcuate line forms part of the linea terminalis and the pelvic brim. The portion of the ilium lying inferiorly to the arcuate line is the pelvic part of the ilium and contributes to the wall of the lesser or true pelvis. The upper part of the ilium expands to form a flat, fan-shaped “wing,” which provides bony support for the lower abdomen, or false pelvis. This part of the ilium provides attachment for muscles functionally associated with the lower limb. The anteromedial surface of the wing is concave and forms the iliac fossa. The external (gluteal) surface of the wing is marked by lines and roughenings and is related to the gluteal region of the lower limb Dr. Rasem Mustafa 22  The entire superior margin of the ilium is thickened to form a prominent crest (the iliac crest), which is the site of attachment for muscles and fascia of the abdomen, back, and lower limb and terminates anteriorly as the anterior superior iliac spine and posteriorly as the posterior superior iliac spine. A prominent tubercle, the tuberculum of the iliac crest, projects laterally near the anterior end of the crest; the posterior end of the crest thickens to form the iliac tuberosity. Dr. Rasem Mustafa 23  Inferior to the anterior superior iliac spine of the crest, on the anterior margin of the ilium, is a rounded protuberance called the anterior inferior iliac spine. This structure serves as the point of attachment for the rectus femoris muscle of the anterior compartment of the thigh and the iliofemoral ligament associated with the hip joint. A less prominent posterior inferior iliac spine occurs along the posterior border of the sacral surface of the ilium, where the bone angles forward to form the superior margin of the greater sciatic notch. Dr. Rasem Mustafa 24  Clinical Correlation  Bone marrow biopsy In certain diseases (e.g.,leukemia),a sample of bone marrow must be obtained to assess the stage and severity of the problem. The iliac crest is often used for such bone marrow biopsies. The iliac crest lies close to the surface and is easily palpated. A bone marrow biopsy is performed by injecting anesthetic in the skin and passing a cutting needle through the corticalbone of the iliac crest. The bone marrow is aspirated and view ed under a microscope. Samples of corticalbone can also be obtained in this w ay to provide information about bone metabolism. Dr. Rasem Mustafa 25 o Pubis  The anterior and inferior part of the pelvic bone is the pubis.  It has a body and two arms (rami). The body is flattened dorsoventrally and articulates with the body of the pubic bone on the other side at the pubic symphysis. The body has a rounded pubic crest on its superior surface that ends laterally as the prominent pubic tubercle. Dr. Rasem Mustafa 26  The superior pubic ramus projects posterolaterally from the body and joins with the ilium and ischium at its base, which is positioned toward the acetabulum. The sharp superior margin of this triangular surface is termed the pecten pubis (pectineal line), which forms part of the linea terminalis of the pelvic bone and the pelvic inlet. Anteriorly, this line is continuous with the pubic crest, which also is part of the linea terminalis and pelvic inlet. The superior pubic ramus is marked on its inferior surface by the obturator groove, which forms the upper margin of the obturator canal. The inferior ramus projects laterally and inferiorly to join with the ramus of the ischium. Dr. Rasem Mustafa 27 o Ischium 3 The ischium is the posterior and inferior part of the pelvic bone. It has: a large body that projects superiorly to join with the ilium and the superior ramus of the pubis, and a ramus that projects anteriorly to join with the inferior ramus of the pubis. The posterior margin of the bone is marked by a prominent ischial spine that separates the lesser sciatic notch, below, from the greater sciatic notch, above. The most prominent feature of the ischium is a large tuberosity (the ischial tuberosity) on the posteroinferior aspect of the bone. This tuberosity is an important site for the attachment of lower limb muscles and for supporting the body when sitting. Dr. Rasem Mustafa 28  Sacrum  The sacrum, which has the appearance of an inverted triangle, is formed by the fusion of the five sacral vertebrae.  The base of the sacrum articulates with vertebra LV, and its apex articulates with the coccyx.  Each of the lateral surfaces of the bone bears a large L-shaped facet for articulation with the ilium of the pelvic bone. Posterior to the facet is a large roughened area for the attachment of ligaments that support the sacro-iliac joint.  The superior surface of the sacrum is characterized by the superior aspect of the body of vertebra SI and is flanked on each side by an expanded wing-like transverse process termed the ala. Dr. Rasem Mustafa 29  The anterior edge of the vertebral body projects forward as the promontory.  The anterior surface of the sacrum is concave; the posterior surface is convex. Because the transverse processes of adjacent sacral vertebrae fuse lateral to the position of the intervertebral foramina and lateral to the bifurcation of spinal nerves into posterior and anterior rami, the posterior and anterior rami of spinal nerves S1 to S4 emerge from the sacrum through separate foramina.  There are four pairs of anterior sacral foramina on the anterior surface of the sacrum for anterior rami, and four pairs of posterior sacral foramina on the posterior surface for the posterior rami. The sacral canal is a continuation of the vertebral canal that terminates as the Dr. Rasem Mustafa 30 sacral hiatus.  Coccyx  The small terminal part of the vertebral column is the coccyx.  Consists of four fused coccygeal vertebrae and, like the sacrum, has the shape of an inverted triangle.  The base of the coccyx is directed superiorly.  The superior surface bears a facet for articulation with the sacrum and two horns, or cornua, one on each side, that project upward to articulate or fuse with similar downward- projecting cornua from the sacrum. These processes are modified superior and inferior articular processes that are present on other vertebrae. Dr. Rasem Mustafa 31  Each lateral surface of the coccyx has a small rudimentary transverse process, extending from the first coccygeal vertebra. Vertebral arches are absent from coccygeal vertebrae; therefore no bony vertebral canal is present in the coccyx. Dr. Rasem Mustafa 32  Joints of the pelvis  Lumbosacral joints The lumbosacraljoints are formed betw een vertebra LV and the sacrum and consist of: the tw o zygapophysial joints, w hich occur betw een adjacent inferior and superior articular processes,and an intervertebraldisc that joins the bodies of vertebrae LV and SI. The lumbosacraljoints are reinforced by strong iliolumbar and lumbosacral ligaments that extend from the expanded transverse processes of vertebra LV to the ilium and theDr. Rasem Mustafa 33 sacrum,respectively.  Sacro-iliac joints They are synovial joints between the L-shaped articular facets on the lateral surfaces of the sacrum and similar facets on the iliac parts of the pelvic bones. Become fibrous with age and may become completely ossified. Each sacro-iliac joint is stabilized by three ligaments: Dr. Rasem Mustafa 34  the anterior sacro-iliac ligament, which is a thickening of the fibrous membrane of the joint capsule and runs anteriorly and inferiorly to the joint. the interosseous sacro-iliac ligament, which is the largest, strongest ligament of the three, and is positioned immediately posterosuperior to the joint and attaches to adjacent expansive roughened areas on the ilium and sacrum, thereby filling the gap between the two bones; and the posterior sacro-iliac ligament, which covers the interosseous sacro-iliac ligament Dr. Rasem Mustafa 35  Pubic symphysis joint The pubic symphysis lies anteriorly between the adjacent surfaces of the pubic bones. Each of the joint’s surfaces is covered by hyaline cartilage and is linked across the midline to adjacent surfaces by fibrocartilage. The joint is surrounded by interwoven layers of collagen fibers and the two major ligaments associated with it are: the superior pubic ligament, located above the joint, and the inferior pubic ligament, located below it. Dr. Rasem Mustafa 36  Orientation In the anatomical position, the pelvis is oriented so that the front edge of the top of the pubic symphysis and the anterior superior iliac spines lie in the same vertical plane. Dr. Rasem Mustafa 37  Differences between men and women The pelvises of women and men differ in a number of ways, many of which have to do with the passing of a baby through a woman’s pelvic cavity during childbirth. The pelvic inlet in women is circular compared with the heart- shaped pelvic inlet in men. The more circular shape is partly caused by the less distinct promontory and broader alae in women. The angle formed by the two arms of the pubic arch is larger in women (80°–85°) than it is in men (50°–60°). The ischial spines generally do not project as far medially into the pelvic cavity in women as they do in men. Dr. Rasem Mustafa 38  Muscles of the pelvic w all  Two muscles, the obturator internus and the piriformis, contribute to the lateral walls of the pelvic cavity. Dr. Rasem Mustafa 39  Obturator internus  The obturator internus is a flat, fan-shaped muscle that originates from the deep surface of the obturator membrane and from associated regions of the pelvic bone that surround the obturator foramen.  The muscle fibers of the obturator internus converge to form a tendon that leaves the pelvic cavity through the lesser sciatic foramen, makes a 90° bend around the ischium between the ischial spine and ischial tuberosity, and then passes posterior to the hip joint to insert on the greater trochanter of the femur.  The obturator internus forms a large part of the anterolateral wall of the pelvic cavity. Piriformis  The piriformis is triangular and originates in the bridges of bone between the four anterior sacral foramina. It passes laterally through the greater sciatic foramen, crosses the posterosuperior aspect of the hip joint, and inserts on the greater trochanter of the femur above the insertion of the obturator internus muscle.  A large part of the posterolateral wall of the pelvic cavity is formed by the piriformis. In addition, this muscle separates the greater sciatic foramen into two regions, one above the muscle and one below. Vessels and nerves coursing between the pelvic cavity and the gluteal region pass through these two regions.40 Dr. Rasem Mustafa   Pelvic floor  The pelvic floor is formed by o Pelvic diaphragm is formed by the levator ani and the coccygeus muscles from both sides. o In the anterior midline, the perineal membrane and the muscles in the deep perineal pouch.  The pelvic floor separates the pelvic cavity, above, from the perineum, below. Dr. Rasem Mustafa 41 o The pelvic diaphragm The pelvic diaphragm is the muscular part of the pelvic floor. Shaped like a bowl or funnel and attached superiorly to the pelvic walls, It consists of the levator ani and the coccygeus muscles. The pelvic diaphragm’s circular line of attachment to the cylindrical pelvic wall passes, on each side, between the greater sciatic foramen and the lesser sciatic foramen. the greater sciatic foramen is situated above the level of the pelvic floor and is a route of communication between the pelvic cavity and the gluteal region of the lower limb; the lesser sciatic foramen is situated below the pelvic floor, providing a route of communication between the gluteal region of the lower limb and the perineum. Dr. Rasem Mustafa 42 Dr. Rasem Mustafa 43  Levator ani The two levator ani muscles originate from each side of the pelvic wall, course medially and inferiorly, and join together in the midline. The attachment to the pelvic wall follows the circular contour of the wall and includes: the posterior aspect of the body of the pubic bone, a linear thickening called the tendinous arch, in the fascia covering the obturator internus muscle, and the spine of the ischium. At the midline, the muscles blend together posterior to the vagina in women and around the anal aperture in both sexes. Posterior to the anal aperture, the muscles come together as a ligament or raphe called the anococcygeal ligament (anococcygeal body) and attaches to the coccyx. Anteriorly, the muscles are separated by a U-shaped defect or gap termed the urogenital hiatus. The margins of this hiatus merge with the walls of the associated viscera and with muscles in the deep perineal pouch below. The hiatus allows the urethra (in both men and women), and the vagina (in women), to pass through the pelvic diaphragm. Dr. Rasem Mustafa 44 o The perineal membrane and deep perineal pouch  The perineal membrane is a thick fascial,triangular structure attached to the bony framew ork of the pubic arch. It is oriented in the horizontal plane and has a free posterior margin. Anteriorly, there is a small gap between the membrane and the inferior pubic ligament (a ligament associated with the pubic symphysis).  The perineal membrane is related above to a thin space called the deep perineal pouch (deep perineal space), which contains a layer of skeletal muscle and various neurovascular elements. Dr. Rasem Mustafa 45  The perineal membrane and adjacent pubic arch provide attachment for the roots of the external genitalia and the muscles associated with them.  The urethra penetrates vertically through a circular hiatus in the perineal membrane as it passes from the pelvic cavity, above, to the perineum, below.  In women, the vagina also passes through a hiatus in the perineal membrane just posterior to the urethral hiatus. Dr. Rasem Mustafa 46  Within the deep perineal pouch, a sheet of skeletal muscle  Functions as a sphincter, mainly for the urethra, and as a stabilizer of the posterior edge of the perineal membrane. Anteriorly, a group of muscle fibers surround the urethra and collectively form the external urethral sphincter. Two additional groups of muscle fibers are associated with the urethra and vagina in women. One group forms the sphincter urethrovaginalis, which surrounds the urethra and vagina as a unit. The second group forms the compressor urethrae, on each side, which originate from the ischiopubic rami and meet anterior to the urethra. Together with the external urethral sphincter, the sphincter urethrovaginalis and compressor urethrae facilitate closing of the urethra. Dr. Rasem Mustafa 47  In both men and women, a deep transverse perineal muscle on each side parallels the free margin of the perineal membrane and joins with its partner at the midline. These muscles are thought to stabilize the position of the perineal body, which is a midline structure along the posterior edge of the perineal membrane. Dr. Rasem Mustafa 48  Perineal body The perineal body is an ill-defined but important connective tissue structure into which muscles of the pelvic floor and the perineum attach. It is positioned in the midline along the posterior border of the perineal membrane, to which it attaches. The posterior end of the urogenital hiatus in the levator ani muscles is also connected to it. The deep transverse perineal muscles intersect at the perineal body; in women, the sphincter urethrovaginalis also attaches to the perineal body. Other muscles that connect to the perineal body include the external anal sphincter, the superficial transverse perineal muscles, and the bulbospongiosus muscles of the perineum. Dr. Rasem Mustafa 49  Pelvic Viscera  The pelvic viscera include I. Pelvic parts of the gastrointestinal system consist mainly of: B. Rectum C. The anal canal D. The terminal part of the sigmoid colon is also in the pelvic cavity II. The urinary system, and III. The reproductive system. Dr. Rasem Mustafa 50 A. Rectum  The rectum is continuous: above, with the sigmoid colon at about the level of vertebra SIII, and below, with the anal canal as this structure penetrates the pelvic floor and passes through the perineum to end as the anus.  The rectum, the most posterior element of the pelvic viscera, is immediately anterior to and follows the concave contour of the sacrum.  The anorectal junction is pulled forward (perineal flexure) by the action of the puborectalis part of the levator ani muscle, so the anal canal moves in a posterior direction as it passes inferiorly through the pelvic floor. Dr. Rasem Mustafa 51  In addition to conforming to the general curvature of the sacrum in the anteroposterior plane, the rectum has three lateral curvatures; the upper and lower curvatures to the right and the middle curvature to the left. The lower part of the rectum is expanded to form the rectal ampulla. Finally, unlike the colon, the rectum lacks distinct taeniae coli muscles, omental appendices, and sacculations (haustra of the colon). Dr. Rasem Mustafa 52 B. Anal canal The anal canal begins at the terminal end of the rectal ampulla where it narrows at the pelvic floor. It terminates as the anus after passing through the perineum. As it passes through the pelvic floor, the anal canal is surrounded along its entire length by the internal and external anal sphincters, which normally keep it closed. The lining of the anal canal bears a number of characteristic structural features that reflect the approximate position of the anococcygeal membrane in the fetus (which closes the terminal end of the developing gastrointestinal system in the fetus) and the transition from gastrointestinal mucosa to skin in the adult Dr. Rasem Mustafa 53  The upper part of the anal canal is lined by mucosa similar to that lining the rectum and is distinguished by a number of longitudinally oriented folds known as anal columns, which are united inferiorly by crescentic folds termed anal valves. Superior to each valve is a depression termed an anal sinus. The anal valves together form a circle around the anal canal at a location known as the pectinate line, which marks the approximate position of the anal membrane in the fetus. Inferior to the pectinate line is a transition zone known as the anal pecten, which is lined by nonkeratinized stratified squamous epithelium. The anal pecten ends inferiorly at the anocutaneous line (“white line”), or where the lining of the anal canal becomes true skin. Dr. Rasem Mustafa 54  Clinical Correlation  Digital rectal examination A digital rectal examination (DRE) is performed by placing the gloved and lubricated index finger into the rectum through the anus. The anal mucosa can be palpated for abnormal masses, and in women, the posterior wall of the vagina and the cervix can be palpated. In men, the prostate can be evaluated for any extraneous nodules or masses. In many instances the digital rectal examination may be followed by proctoscopy or colonoscopy. An ultrasound probe may be placed into the rectum to assess the gynecological structures in females and the prostate in the male before performing a prostatic biopsy. A digital rectal examination also allows detection of fresh or altered blood in the rectum in patients with acute gastrointestinal bleeding or chronic anemia. Dr. Rasem Mustafa 55  Carcinoma of the colon and rectum Carcinoma of the colon and rectum (colorectum) is a common and often lethal disease. Recent advances in surgery, radiotherapy, and chemotherapy have only slightly improved 5-year survival rates. The biological behavior of tumors of the colon and rectum is relatively predictable. Most of the tumors develop from benign polyps, some of which undergo malignant change. The overall prognosis is related to: the degree of tumor penetration through the bowel wall, the presence or absence of lymphatic dissemination, and the presence or absence of systemic metastases. Dr. Rasem Mustafa 56  Given the position of the colon and rectum in the abdominopelvic cavity and its proximity to other organs, it is extremely important to accurately stage colorectal tumors;  a tumor in the pelvis, for example, could invade the uterus or bladder. Assessing whether or not spread has occurred usually involves computed tomography (assessment for distal metastases) and magnetic resonance imaging (local staging). Endoscopic ultrasound (EUS) is also used in some instances for local staging of rectal cancer. Dr. Rasem Mustafa 57 II. Urinary system The pelvic parts of the urinary system consist of the terminal parts of the ureters, the bladder, and the proximal part of the urethra.  Ureters The ureters enter the pelvic cavity from the abdomen by passing through the pelvic inlet. On each side, the ureter crosses the pelvic inlet and enters the pelvic cavity in the area anterior to the bifurcation of the common iliac artery. From this point, it continues along the pelvic wall and floor to join the base of the bladder. In the pelvis, the ureter is crossed by: the ductus deferens in men, and the uterine artery in women Dr. Rasem Mustafa 58  Bladder The bladder is the most anterior element of the pelvic viscera. Although it is entirely situated in the pelvic cavity when empty, it expands superiorly into the abdominal cavity when full. The empty bladder is shaped like a three-sided pyramid that has tipped over to lie on one of its margins. It has an apex, a base, a superior surface, and two inferolateral surfaces. Dr. Rasem Mustafa 59  The apexof the bladder is directed toward the top of the pubic symphysis; a structure known as the median umbilical ligament. The base of the bladder is shaped like an inverted triangle and faces posteroinferiorly. The two ureters enter the bladder at each of the upper corners of the base, and the urethra drains inferiorly from the lower corner of the base. (Trigone). The inferolateral surfaces of the bladder are cradled between the levator ani muscles of the pelvic diaphragm and the adjacent obturator internus muscles above the attachment of the pelvic diaphragm. The superior surface is slightly domed when the bladder is empty; it balloons upward as the bladder fills. Dr. Rasem Mustafa 60  Neck of bladder The neck of the bladder surrounds the origin of the urethra at the point where the two inferolateral surfaces and the base intersect. The neck is the most inferior part of the bladder and also the most “fixed” part. It is anchored into position by a pair of tough fibromuscular bands, which connect the neck and pelvic part of the urethra to the posteroinferior aspect of each pubic bone. Dr. Rasem Mustafa 61  In women, these fibromuscular bands are termed pubovesical ligaments. Together with the perineal membrane and associated muscles, the levator ani muscles, and the pubic bones, these ligaments help support the bladder. In men, the paired fibromuscular bands are known as puboprostatic ligaments because they blend with the fibrous capsule of the prostate, which surrounds the neck of the bladder and adjacent part of the urethra. Although the bladder is considered to be pelvic in the adult, it has a higher position in children. At birth, the bladder is almost entirely abdominal; the urethra begins approximately at the upper margin of the pubic symphysis. With age, the bladder descends until after puberty when it assumes the adult position. Dr. Rasem Mustafa 62  Clinical Correlation  Suprapubic catheterization In certain instances it is necessary to catheterize the bladder through the anterior abdominal wall. For example, when the prostate is markedly enlarged and it is impossible to pass a urethral catheter, a suprapubic catheter may be placed. The bladder is a retroperitoneal structure and when full lies adjacent to the anterior abdominal wall. Ultrasound visualization of the bladder may be useful in assessing the size of this structure and, importantly, differentiating this structure from other potential abdominal masses. The procedure of suprapubic catheterization is straightforward and involves the passage of a small catheter on a needle in the midline approximately 2 cm above the pubic symphysis. The catheter passes easily into the bladder without compromise of other structures and permits free drainage. Dr. Rasem Mustafa 63  Bladder cancer Bladder cancer is the most common tumor of the urinary tract and is usually a disease of the sixth and seventh decades, although there is an increasing trend for younger patients to develop this disease. Approximately one-third of bladder tumors are multifocal; fortunately, two-thirds are superficial tumors and amenable to local treatment. Bladder tumors may spread through the bladder wall and invade local structures, including the rectum, uterus (in women), and lateral walls of the pelvic cavity. Prostatic involvement is not uncommon in male patients. The disease spreads via the internal iliac lymph nodes. Spread to distant metastatic sites rarely includes the lung. Dr. Rasem Mustafa 64  Large bladder tumors may produce complications, including invasion and obstruction of the ureters. Ureteric obstruction can then obstruct the kidneys and induce kidney failure. Moreover, bladder tumors can invade other structures of the pelvic cavity. Treatment o for early-stage tumors includes local resection with preservation of the bladder. o Diffuse tumors may be treated with local chemotherapy; o more extensive tumors may require radical surgical removal of the bladder (cystectomy) and, in men, the prostate (prostatectomy). o Bladder reconstruction (formation of so-called neobladder) is performed in patients after cystectomy using part of a bowel, most commonly the ileum. Dr. Rasem Mustafa 65  Urethra The urethra begins at the base of the bladder and ends with an external opening in the perineum. The paths taken by the urethra differ significantly in women and men. In women In women, the urethra is short, being about 4 cm long. It travels a slightly curved course as it passes inferiorly through the pelvic floor into the perineum, where it passes through the deep perineal pouch and perineal membrane before opening in the vestibule that lies between the labia minora. Dr. Rasem Mustafa 66  The urethral opening is anterior to the vaginal opening in the vestibule. The inferior aspect of the urethra is bound to the anterior surface of the vagina. Two small para-urethral mucous glands (Skene’s glands) are associated with the lower end of the urethra. Each drains via a duct that opens onto the lateral margin of the external urethral orifice. Dr. Rasem Mustafa 67  In men In men, the urethra is long, about 20 cm, and bends twice along its course. Beginning at the base of the bladder and passing inferiorly through the prostate, it passes through the deep perineal pouch and perineal membrane and immediately enters the root of the penis. As the urethra exits the deep perineal pouch, it bends forward to course anteriorly in the root of the penis. When the penis is flaccid, the urethra makes another bend, this time inferiorly, when passing from the root to the body of the penis. During erection, the bend between the root and body of the penis disappears. Dr. Rasem Mustafa 68  The urethra in men is divided into preprostatic, prostatic, membranous, and spongy parts. Preprostatic part. The preprostatic part of the urethra is about 1 cm long, extends from the base of the bladder to the prostate, and is associated with a circular cuff of smooth muscle fibers (the internal urethral sphincter). Contraction of this sphincter prevents retrograde movement of semen into the bladder during ejaculation. Prostatic part. The prostatic part of the urethra is 3 to 4 cm long and is surrounded by the prostate. In this region, the lumen of the urethra is marked by a longitudinal midline fold of mucosa (the urethral crest). The depression on each side of the crest is the prostatic sinus; the ducts of the prostate empty into these two sinuses. Dr. Rasem Mustafa 69  Membranous part. The membranous part of the urethra is narrow and passes through the deep perineal pouch. During its transit through this pouch, the urethra, in both men and women, is surrounded by skeletal muscle of the external urethral sphincter. Spongy urethra. The spongy urethra is surrounded by erectile tissue (the corpus spongiosum) of the penis. It is enlarged to form a bulb at the base of the penis and again at the end of the penis to form the navicular fossa. The two bulbo-urethral glands in the deep perineal pouch are part of the male reproductive system and open into the bulb of the spongy urethra. The external urethral orifice is the sagittal slit at the end of the penis. Dr. Rasem Mustafa 70  Clinical Correlation  Bladder infection The relatively short length of the urethra in women makes them more susceptible than men to bladder infection. The primary symptom of urinary tract infection in women is usually inflammation of the bladder (cystitis). The infection can be controlled in most instances by oral antibiotics and resolves without complication. In children under 1 year of age, infection from the bladder may spread via the ureters to the kidneys, where it can produce renal damage and ultimately lead to renal failure. Early diagnosis and treatment are necessary. Dr. Rasem Mustafa 71  Urethral catheterization Urethral catheterization is often performed to drain urine from a patient’s bladder when the patient is unable to micturate. When inserting urinary catheters, it is important to appreciate the gender anatomy of the patient. In men: The spongy urethra is surrounded by the erectile tissue of the bulb of the penis immediately inferior to the deep perineal pouch. The wall of this short segment of urethra is relatively thin and angles superiorly to pass through the deep perineal pouch; at this position the urethra is vulnerable to damage, notably during cystoscopy. The membranous part of the urethra runs superiorly as it passes through the deep perineal pouch. The prostatic part of the urethra takes a slight concave curve anteriorly as it passes through the prostate gland. In women, it is much simpler to pass catheters and cystoscopes because the urethra is short and straight. Urine may therefore be readily drained from a distended bladder without significant concernDr.for urethral rupture. Rasem Mustafa 72 III. Reproductive system A. In men  The reproductive system in men has components in the abdomen, pelvis, and perineum.  The major components are  a testis,  epididymis,  ductus deferens, and  ejaculatory duct on each side, and  the urethra and  penis in the midline.  In addition, three types of accessory glands are associated with the system: a single prostate, a pair of seminal vesicles, and a pair of bulbo-urethral glands.  The design of the reproductive system in men is basically a series of ducts and tubules. The arrangement of parts and linkage to theDr.urinary Rasem Mustafa 73 tract reflects its embryological development.  Testes The testes originally develop high on the posterior abdominal wall and then descend, normally before birth, through the inguinal canal in the anterior abdominal wall and into the scrotum of the perineum. During descent, the testes carry their vessels, lymphatics, and nerves, as well as their principal drainage ducts, the ductus deferens (vas deferens) with them. The lymph drainage of the testes is therefore to the lateral aortic or lumbar nodes and pre-aortic nodes in the abdomen, and not to the inguinal or pelvic lymph nodes. Each ellipsoid-shaped testis is enclosed within the end of an elongated musculofascial pouch, which is continuous with the anterior abdominal wall and projects into the scrotum. The spermatic cord is the tube-shaped connection between the pouch in the scrotum and the abdominal wall. Dr. Rasem Mustafa 74  The sides and anterior aspect of the testis are covered by a closed sac of peritoneum (the tunica vaginalis), which originally connected to the abdominal cavity. Normally after testicular descent, the connection closes, leaving a fibrous remnant. Dr. Rasem Mustafa 75  Epididymis The epididymis courses along the posterolateral side of the testis. It has two distinct components: the efferent ductules, which form an enlarged coiled mass that sits on the posterior superior pole of the testis and forms the head of the epididymis; and the true epididymis, which is a single, long coiled duct into which the efferent ductules all drain, and which continues inferiorly along the posterolateral margin of the testis as the body of the epididymis and enlarges to form the tail of the epididymis at the inferior pole of the testis. During passage through the epididymis, spermatozoa acquire the ability to move and fertilize an egg. The epididymis also stores spermatozoa until ejaculation. The end of the epididymis is continuous with the ductus deferens. Dr. Rasem Mustafa 76  Ductus deferens The ductus deferens is a long muscular duct that transports spermatozoa from the tail of the epididymis in the scrotum to the ejaculatory duct in the pelvic cavity. It ascends in the scrotum as a component of the spermatic cord and passes through the inguinal canal in the anterior abdominal wall. After passing through the deep inguinal ring, the ductus deferens bends medially around the lateral side of the inferior epigastric artery and crosses the external iliac artery and the external iliac vein at the pelvic inlet to enter the pelvic cavity. Connect with the prostatic urethra. Dr. Rasem Mustafa 77  Seminal vesicle Each seminal vesicle is an accessory gland of the male reproductive system that develops as a blind-ended tubular outgrowth from the ductus deferens. The seminal vesicle is immediately lateral to and follows the course of the ductus deferens at the base of the bladder. The duct of the seminal vesicle joins the ductus deferens to form the ejaculatory duct. Dr. Rasem Mustafa 78  Prostate The prostate is an unpaired accessory structure of the male reproductive system that surrounds the urethra in the pelvic cavity. It lies immediately inferior to the bladder, posterior to the pubic symphysis, and anterior to the rectum. The prostate is shaped like an inverted rounded cone with a larger base, which is continuous above with the neck of the bladder, and a narrower apex, which rests below on the pelvic floor. The prostate develops as 30 to 40 individual complex glands, which grow from the urethral epithelium into the surrounding wall of the urethra. Secretions from the prostate, together with secretions from the seminal vesicles, contribute to the formation of semen during ejaculation. Dr. Rasem Mustafa 79  Bulbo-urethral glands The bulbo-urethral glands, one on each side, are small, pea-shaped mucous glands situated within the deep perineal pouch. They are lateral to the membranous part of the urethra. The duct from each gland passes inferomedially through the perineal membrane, to open into the bulb of the spongy urethra at the root of the penis. Together with small glands positioned along the length of the spongy urethra, the bulbo-urethral glands contribute to lubrication of the urethra and the pre-ejaculatory emission from the penis. Dr. Rasem Mustafa 80 III. Reproductive system B. In women  The reproductive tract in women is contained mainly in the pelvic cavity and perineum, although during pregnancy, the uterus expands into the abdominal cavity.  Major components of the system consist of:  Ovary on each side, and  Uterus,  Vagina  Clitoris in the midline.  In addition, a pair of accessory glands (the greater vestibular glands) are associated with the tract. Dr. Rasem Mustafa 81  Ovaries Like the testes in men, the ovaries develop high on the posterior abdominal wall and then descend before birth, bringing with them their vessels, lymphatics, and nerves. Unlike the testes, the ovaries do not migrate through the inguinal canal into the perineum, but stop short and assume a position on the lateral wall of the pelvic cavity. The ovaries are the sites of egg production (oogenesis). Mature eggs are ovulated into the peritoneal cavity and normally directed into the adjacent openings of the uterine tubes by cilia on the ends of the uterine tubes. The ovaries lie adjacent to the lateral pelvic wall just inferior to the pelvic inlet. Each of the two almond-shaped ovaries is about 3 cm long and is suspended by a mesentery (the mesovarium) that is a posterior Dr. Rasem Mustafa 82  Uterus The uterus is a thick-walled muscular organ in the midline between the bladder and rectum. It consists of a body and a cervix, and inferiorly it joins the vagina. Superiorly, uterine tubes project laterally from the uterus and open into the peritoneal cavity immediately adjacent to the ovaries. The body of the uterus is flattened anteroposteriorly and, above the level of origin of the uterine tubes, has a rounded superior end (fundus of the uterus). The cavity of the body of the uterus is a narrow slit, when viewed laterally, and is shaped like an inverted triangle, when viewed anteriorly. Each of the superior corners of the cavity is continuous with the lumen of a uterine tube; the inferior corner is continuous with the central canal of the cervix. Dr. Rasem Mustafa 83  Uterine tubes The uterine tubes extend from each side of the superior end of the body of the uterus to the lateral pelvic wall and are enclosed within the upper margins of the mesosalpinx portions of the broad ligaments. Because the ovaries are suspended from the posterior aspect of the broad ligaments, the uterine tubes pass superiorly over, and terminate laterally to, the ovaries. Dr. Rasem Mustafa 84  Each uterine tube has an expanded trumpet-shaped end (the infundibulum), which curves around the superolateral pole of the related ovary. The margin of the infundibulum is rimmed with small finger-like projections termed fimbriae. The lumen of the uterine tube opens into the peritoneal cavity at the narrowed end of the infundibulum. Medial to the infundibulum, the tube expands to form the ampulla and then narrows to form the isthmus, before joining with the body of the uterus. The fimbriated infundibulum facilitates the collection of ovulated eggs from the ovary. Fertilization normally occurs in the ampulla. Dr. Rasem Mustafa 85  Cervix The cervix forms the inferior part of the uterus and is shaped like a short, broad cylinder with a narrow central channel. The body of the uterus normally arches forward (anteflexed on the cervix) over the superior surface of the emptied bladder. In addition, the cervix is angled forward (anteverted) on the vagina so that the inferior end of the cervix projects into the upper anterior aspect of the vagina. Because the end of the cervix is dome shaped, it bulges into the vagina, and a gutter, or fornix, is formed around the margin of the cervix where it joins the vaginal wall. The tubular central canal of the cervix opens, below, as the external os, into the vaginal cavity and, above, as the internal os, into the uterine cavity. Dr. Rasem Mustafa 86  Vagina The vagina is the copulatory organ in women. It is a distensible fibromuscular tube that extends from the perineum through the pelvic floor and into the pelvic cavity. The internal end of the canal is enlarged to form a region called the vaginal vault. The anterior wall of the vagina is related to the base of the bladder and to the urethra; in fact, the urethra is embedded in, or fused to, the anterior vaginal wall. Posteriorly, the vagina is related principally to the rectum. Inferiorly, the vagina opens into the vestibule of the perineum immediately posterior to the external opening of the urethra. Dr. Rasem Mustafa 87  From its external opening (the introitus), the vagina courses posterosuperiorly through the perineal membrane and into the pelvic cavity, where it is attached by its anterior wall to the circular margin of the cervix. The vaginal fornixis the recess formed between the margin of the cervix and the vaginal wall. Based on position, the fornix is subdivided into a posterior fornix, an anterior fornix, and two lateral fornices. The vaginal canal is normally collapsed so that the anterior wall is in contact with the posterior wall. Dr. Rasem Mustafa 88  Pelvic fascia Fascia in the pelvic cavity lines the pelvic walls, surrounds the bases of the pelvic viscera, and forms sheaths around blood vessels and nerves that course medially from the pelvic walls to reach the viscera in the midline. This pelvic fascia is a continuation of the extraperitoneal connective tissue layer found in the abdomen. Dr. Rasem Mustafa 89  In women In women, a rectovaginal septum separates the posterior surface of the vagina from the rectum. Condensations of fascia form ligaments that extend from the cervix to the anterior (pubocervical ligament), lateral (transverse cervical or cardinal ligament), and posterior (uterosacral ligament) pelvic walls. These ligaments, together with the perineal membrane, the levator ani muscles, and the perineal body, are thought to stabilize the uterus in the pelvic cavity. The most important of these ligaments are the transverse cervical or cardinal ligaments, which extend laterally from each side of the cervix and vaginal vault to the related pelvic wall. Dr. Rasem Mustafa 90  In men In men, a condensation of fascia around the anterior and lateral region of the prostate (prostatic fascia) contains and surrounds the prostatic plexus of veins and is continuous posteriorly with the rectovesical septum, which separates the posterior surface of the prostate and base of the bladder from the rectum. Dr. Rasem Mustafa 91  Peritoneum of the pelvis The peritoneum of the pelvis is continuous at the pelvic inlet with the peritoneum of the abdomen. In the pelvis, the peritoneum drapes over the pelvic viscera in the midline, forming: pouches between adjacent viscera, and folds and ligaments between viscera and pelvic walls. Anteriorly, median and medial umbilical folds of peritoneum cover the embryological remnants of the urachus and umbilical arteries. Posteriorly, peritoneum drapes over the anterior and lateral aspects of the upper third of the rectum, but only the anterior surface of the middle third of the rectum is covered by peritoneum; the lower third of the rectum is not covered at all. Dr. Rasem Mustafa 92  In women shallow vesico-uterine pouch occurs anteriorly, between the bladder and uterus, and a deep recto-uterine pouch (pouch of Douglas) occurs posteriorly, between the uterus and rectum. In addition, a large fold of peritoneum (the broad ligament), with a uterine tube enclosed in its superior margin and an ovary attached posteriorly, is located on each side of the uterus and extends to the lateral pelvic walls. Dr. Rasem Mustafa 93  Broad ligament The broad ligament is a sheet- like fold of peritoneum, oriented in the coronal plane that runs from the lateral pelvic wall to the uterus, and encloses the uterine tube in its superior margin and suspends the ovary from its posterior aspect. The uterine arteries cross the ureters at the base of the broad ligaments, and the ligament of the ovary and round ligament of the uterus are enclosed within the parts of the broad ligament related to the ovary and uterus, respectively. Dr. Rasem Mustafa 94  The ovarian vessels, nerves, and lymphatics enter the superior pole of the ovary from a lateral position and are covered by another raised fold of peritoneum, which with the structures it contains forms the suspensory ligament of the ovary (infundibulopelvic ligament). The inferior pole of the ovary is attached to a fibromuscular band of tissue (the ligament of the ovary), which courses medially in the margin of the mesovarium to the uterus and then continues anterolaterally as the round ligament of the uterus. The round ligament of the uterus passes over the pelvic inlet to reach the deep inguinal ring and then courses through the inguinal canal to end in connective tissue related to the labium majus in the perineum. Both the ligament of the ovary and the round ligament of the uterus are remnants of the gubernaculum, which attaches the gonad to the labioscrotal swellings in the embryo. Dr. Rasem Mustafa 95  In men In men, the visceral peritoneum drapes over the top of the bladder onto the superior poles of the seminal vesicles and then reflects onto the anterior and lateral surfaces of the rectum. A rectovesical pouch occurs between the bladder and rectum. Dr. Rasem Mustafa 96  Nerves in the pelvic cavity  Sacral and coccygeal plexuses  The sacral and coccygeal plexuses are situated on the posterolateral wall of the pelvic cavity and generally occur in the plane between the muscles and blood vessels.  They are formed by the ventral rami of S1 to Co, with a significant contribution from L4 and L5, which enter the pelvis from the lumbar plexus.  Nerves from these mainly somatic plexuses contribute to the innervation of the lower limb and muscles of the pelvis and perineum. Cutaneous branches supply skin over the medial side of the foot, the posterior aspect of the lower limb, and most of the perineum. Dr. Rasem Mustafa 97  Pudendal nerve. The pudendal nerve forms anteriorly to the lower part of the piriformis muscle from ventral divisions of S2 to S4. It: leaves the pelvic cavity through the greater sciatic foramen, inferior to the piriformis muscle, and enters the gluteal region; courses into the perineum by immediately passing around the sacrospinous ligament, where the ligament joins the ischial spine, and through the lesser sciatic foramen (this course takes the nerve out of the pelvic cavity, around the peripheral attachment of the pelvic floor, and into the perineum); Dr. Rasem Mustafa 98  is accompanied throughout its course by the internal pudendal vessels; and innervates skin and skeletal muscles of the perineum, including the external anal and external urethral sphincters. Dr. Rasem Mustafa 99  Arteries  The major artery of the pelvis and perineum is  Internal iliac artery on each side.  In addition to providing a blood supply to most of the pelvic viscera, pelvic walls and floor, and structures in the perineum, including erectile tissues of the clitoris and the penis,  This artery gives rise to branches that follow nerves into the gluteal region of the lower limb.  Other vessels that originate in the abdomen and contribute to the supply of pelvic structures include the  M edian sacral artery and, in women, the ovarian arteries. Dr. Rasem Mustafa 100  Internal iliac artery  The internal iliac artery originates from the common iliac artery on each side, approximately at the level of the intervertebral disc between LV and SI, and lies anteromedial to the sacro-iliac joint.  The vessel courses inferiorly over the pelvic inlet and then divides at the level of the superior border of the greater sciatic foramen into:  Anterior trunk  posterior trunks  Branches from the posterior trunk contribute to the supply of the lower posterior abdominal wall, the posterior pelvic wall, and the gluteal region. Branches from the anterior trunk supply the pelvic viscera, the perineum, the gluteal region, the adductor region of the thigh, and, in the fetus, the placenta. Dr. Rasem Mustafa 101  Posterior trunk Branches of the posterior trunk of the internal iliac artery are the iliolumbar artery, the lateral sacral artery, and the superior gluteal artery. The iliolumbar artery ascends laterally back out of the pelvic inlet and divides into a lumbar branch and an iliac branch. The lumbar branch contributes to the supply of the posterior abdominal wall, psoas and quadratus lumborum muscles, and cauda equina, via a small spinal branch that passes through the intervertebral foramen between LV and SI. The iliac branch passes laterally into the iliac fossa to supply muscle and bone. Dr. Rasem Mustafa 102  The lateral sacral arteries, usually two, originate from the posterior division of the internal iliac artery. They give rise to branches that pass into the anterior sacral foramina to supply related bone and soft tissues, structures in the vertebral (sacral) canal, and skin and muscle posterior to the sacrum. The superior gluteal artery is the largest branch of the internal iliac artery and is the terminal continuation of the posterior trunk. This vessel makes a substantial contribution to the blood supply of muscles and skin in the gluteal region and also supplies branches to adjacent muscles and bones of the pelvic walls. Dr. Rasem Mustafa 103  Anterior trunk Branches of the anterior trunk of the internal iliac artery include the superior vesical artery, the umbilical artery, the inferior vesical artery, the middle rectal artery, the uterine artery, the vaginal artery, the obturator artery, the internal pudendal artery, and the inferior gluteal artery Dr. Rasem Mustafa 104  The first branch of the anterior trunk is the umbilical artery, which gives origin to the superior vesical artery. In the fetus, the umbilical artery is large and carries blood from the fetus to the placenta. After birth, the fibrous remnant of the umbilical artery itself is the medial umbilical ligament. The superior vesical artery normally originates from the root of the umbilical artery, supply the superior aspect of the bladder and distal parts of the ureter. In men, it also may give rise to an artery that supplies the ductus deferens. Dr. Rasem Mustafa 105  The inferior vesical artery occurs in men and supplies branches to the bladder, ureter, seminal vesicle, and prostate. The vaginal artery in women is the equivalent of the inferior vesical artery in men and supplies branches to the vagina and to adjacent parts of the bladder and rectum. The middle rectal artery courses medially to supply the rectum. The vessel anastomoses with the superior rectal artery, which originates from the inferior mesenteric artery in the abdomen, and the inferior rectal artery, which originates from the internal pudendal artery in the perineum. Dr. Rasem Mustafa 106  The obturator artery together with the obturator nerve, above, and obturator vein, below, it enters and supplies the adductor region of the thigh. The internal pudendal artery association with the pudendal nerve on its medial side, it is the main artery of the perineum. Among the structures it supplies are the erectile tissues of the clitoris and the penis. The inferior gluteal artery is a large terminal branch of the anterior trunk of the internal iliac artery. It contributes to the blood supply of the gluteal region and anastomoses with a network of vessels around the hip joint. Dr. Rasem Mustafa 107  The uterine artery in women courses medially and anteriorly in the base of the broad ligament to reach the cervix, it is the major blood supply to the uterus and enlarges significantly during pregnancy. Through anastomoses with other arteries, the vessel contributes to the blood supply of the ovary and vagina as well. Dr. Rasem Mustafa 108  Ovarian arteries In women, the gonadal (ovarian) vessels originate from the abdominal aorta and then descend to cross the pelvic inlet and supply the ovaries. They anastomose with terminal parts of the uterine arteries. On each side, the vessels travel in the suspensory ligament of the ovary (the infundibulopelvic ligament) as they cross the pelvic inlet to the ovary. Branches pass through the mesovarium to reach the ovary and through the mesometrium of the broad ligament to anastomose with the uterine artery. The ovarian arteries enlarge significantly during pregnancy to augment the uterine blood supply. Dr. Rasem Mustafa 109  M edian sacral artery The median sacral artery originates from the posterior surface of the aorta just superior to the aortic bifurcation at vertebral level LIV in the abdomen. It descends in the midline, crosses the pelvic inlet, and then courses along the anterior surface of the sacrum and coccyx. It gives rise to the last pair of lumbar arteries and to branches that anastomose with the iliolumbar and lateral sacral arteries. Dr. Rasem Mustafa 110  Veins Pelvic veins follow the course of all branches of the internal iliac artery except for the umbilical artery and the iliolumbar artery.  Lymphatics Lymphatics from most pelvic viscera drain mainly into lymph nodes distributed along the internal iliac and external iliac arteries and their associated branches, which drain into nodes associated with the common iliac arteries and then into the lateral aortic or lumbar nodes associated with the lateral surfaces of the abdominal aorta. In turn, these lateral aortic or lumbar nodes drain into the lumbar trunks, which continue to the origin of the thoracic duct at approximately vertebral level TXII. Dr. Rasem Mustafa 111