For educational and institutional use. This test bank is licensed for noncommercial, educational inhouse or online educational course use only in

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1 For educational and institutional use. This test bank is licensed for noncommercial, educational inhouse or online educational course use only in educational and corporate institutions. Any broadcast, duplication, circulation, public viewing, conference viewing or Internet posting of this product is strictly prohibited. Purchase of the product constitutes an agreement to these terms. In return for the licensed use, the Licensee hereby releases, and waives any and all claims and/or liabilities that may arise against ASRT as a result of the product and its licensing.

2 Sectional Anatomy Essentials Module 8: The Pelvis 1. The Extremities Welcome to Sectional Anatomy Essentials Module 8: The Pelvis. This module was written by Michael A. Manders, BS, R.R.A., R.T. (R), and Jeffrey D. Houston, MD. 2. License Agreement and Disclaimer 3. Objectives After completing this module, you will be able to: Describe the 3 bones that form the pelvic girdle. Name and locate the contents of the lower abdominal cavity. Locate and describe the function of the pelvic muscles. Identify and describe the location and function of the pelvic organs. Track the flow of urine within the pelvic region. Identify and describe the location and function of the components of the male reproductive system. Identify and describe the location and function of the components of the female reproductive system. Follow the course of arterial and venous blood flow within the pelvis. 4. Introduction Throughout the Sectional Anatomy Essentials series, we display most of the cross-sectional anatomy using multidetector computed tomography (CT) and magnetic resonance (MR) images to illustrate the three-dimensional relationship of the structures. Use the slider bar in this animation to scroll through the images. Because you can easily lose your frame of reference when viewing cross-sectional images, the location of the featured slice on many slides will be displayed on adjacent localizer images of the other 2 planes, like the image shown here. Click on the next button when you are ready to proceed. 5. Surface Lines As we begin our discussion of the pelvis, it s important to mention surface lines. These arbitrary lines are used to reference the location of different structures inside the pelvis. The surface lines include the midsternal line and the umbilical line. The midsternal, or midsagittal, line evenly divides the body into right and left halves. The umbilical line extends horizontally through the umbilicus, or belly button. These surface lines are used to divide the abdomen into quadrants, as you ll discover shortly. 6. The 4-Region Method There are 2 accepted ways to divide the abdomen and pelvis, the 4-region and the 9-region methods, each using different surface lines. The 4-region method uses the midsternal line and the umbilical line to divide the abdomen and pelvis into 4 quadrants: the right upper quadrant, the left upper quadrant, the left lower quadrant and the right lower quadrant. In this module, we ll focus on the right and left lower quadrants. It s important to remember that each person is a little different internally, so the descriptions of what organs are typically located in each region may not be exactly the same for everyone.

3 7. The 4-Region Method The right lower quadrant typically contains the cecum, the appendix, a portion of the ascending colon, the right fallopian tube, the right ovary and a portion of the right ureter. The left lower quadrant typically contains the sigmoid colon, a portion of the descending colon, the left fallopian tube, the left ovary and a portion of the left ureter. 8. The 9-Region Method The 9-region method uses 4 lines, 2 vertical and 2 horizontal, to divide the inferior chest, abdomen and pelvis into 9 regions. Also known as the planes of Addison, these regions are useful in clinical medicine because specific disease processes can present as pain and tenderness in specific areas. A clinician who is familiar with these clinical presentations can sometimes spare the patient from the radiation dose and cost associated with diagnostic imaging, particularly computed tomography. In this module, we ll only focus on the 6 inferior regions: right lumbar, umbilicus, left lumbar region, right iliac, hypogastric and left iliac regions. 9. Lumbar and Umbilical Regions The right and left lumbar regions are found directly inferior to the right and left hypochondrium regions. They extend medially from the lateral abdominal wall and are bordered superiorly by the transpyloric plane and inferiorly by the transtubercular plane. Organs located in the right lumbar region include the inferior portion of the liver, gallbladder, portions of the small intestine and ascending colon, and a portion of the right kidney. The left lumbar region contains portions of the small intestine and descending colon, and a portion of the left kidney. The umbilical region is located between the right and left lumbar regions. It typically contains a portion of the stomach, the pancreas, portions of the small intestine and the majority of the transverse colon, as well as portions of the right and left kidneys and ureters. 10. Iliac Regions The right and left iliac regions extend medially from the lateral pelvis and are bordered superiorly by the transtubercular plane. Organs located in the right iliac region include the appendix, the cecum, the right ovary, the right fallopian tube, and portions of the small intestine and ascending colon. The left iliac region contains portions of the small intestine, the sigmoid colon and descending colon, the left ovary, and the left fallopian tube. The hypogastric, or pubic, region is located between the right and left iliac regions. It typically contains portions of the small intestine, the sigmoid colon, the right and left fallopian tubes, and the right and left ureters, as well as the rectum, the urinary bladder, the uterus, the vas deferens, the seminal vesicles and the prostate. 11. Bony Pelvis The skeletal portion of the pelvis is more commonly known as the bony pelvis. It bears the weight of the body when a person sits and distributes that weight to the legs when a person walks. It also provides attachment points for many of the muscles of the abdomen, pelvis and lower extremities. We ll discuss 3 primary components of the bony pelvis: the sacrum, the coccyx and the os coxae.

4 12. Sacrum The sacrum is a unique bone that looks like a bat when viewed in the axial plane. It is located inferior to the lumbar spine and in between the right and left iliac bones. It typically is made up of 5 bones that fuse into a single triangular-shaped structure by the age of 26. The sacrum consists of a body, paired ala, a sacral canal and paired articular processes. The blocks of bone located lateral to the sacral foramina form the lateral masses of the sacrum. Lateral to each sacral ala, or wing, are the iliac crests of the pelvis. The joints between the ala and the iliac crests are called the sacroiliac joints. A prominent lip of bone projecting anterosuperiorly from S1 is called the sacral promontory. Along the posterior midline border of the sacrum is the sacral crest, the fused rudimentary spinous processes of the sacral vertebrae. The laminae of the fifth sacral vertebra typically fail to unite, producing a defect in the posterior wall of the sacral canal called the sacral hiatus. The sacral cornua are rounded processes that project inferiorly from the fifth sacral vertebra and articulate with the cornua of the coccyx. 13. The Sacrum Scroll through this animation to see all of the sacrum structures we just discussed. 14. Sacroiliac Joints There are 2 sacroiliac joints one on the right and one on the left. Held together by strong ligaments, these joints are capable of some movement. The articulating surfaces of the sacrum and ilium form an uneven contour about the time we begin to walk. These ridges and depressions work like a zipper, and with the assistance of the ligaments, lock the sacrum in place between the right and left ilium. The primary function of the sacroiliac joints is shock absorption. Seronegative spondyloarthropathies are a group of arthritic autoimmune diseases that affect the axial skeleton but do not exhibit rheumatoid factor, meaning that they follow a different pathological mechanism than typical rheumatoid arthritis. Typically, these diseases first involve the sacroiliac joints, making the joints an important anatomic landmark. The most common disease of the group is ankylosing spondylitis, but others include Reiter syndrome, enteropathic spondylitis, psoriatic arthritis and isolated acute anterior uveitis. In severe cases, the sacroiliac joints can fuse completely, making them essentially disappear on imaging studies. 15. Coccyx The most inferior portion of the spine is the coccyx. The coccyx is commonly referred to as the tailbone because it s thought to be the remnant of a vestigial tail. A vestigial structure is one that has lost all or most of its function through human evolution. The coccyx, however, still serves as the attachment point for many ligaments and muscles. The coccyx usually is formed from 4 vertebrae. Whereas the first 3 coccygeal vertebrae have a basic vertebral format consisting of a vertebral body with articular and transverse processes, the fourth segment is typically an osseous stub arising from the inferior coccyx.

5 16. Os coxae The third portion of the bony pelvis that we ll discuss is the os coxae, commonly known as the hip bone. Located bilaterally, each hip bone is made up of 3 different bones: the ilium, the pubis and the ischium. These three bones unite at an area called the acetabulum, the socket-type joint that receives the femoral head. 17. Ilium First, we ll look at the parts of the ilium: the body and the ala. The body is located inferiorly and makes up a small portion of the ilium. It helps form approximately 40% of the acetabulum. 18. Ilium Arising superiorly from the body of each ilium is the ala, or wing. Each ala consists of numerous parts, the first of which is the iliac fossa. The iliac fossa is a concave depression located in the middle of each ala. Superiorly, each iliac fossa is bordered by the iliac crest. The iliac crests also make up the superolateral borders of the pelvis as a whole. Forming the inferior border of each iliac fossa is the arcuate line. The arcuate line is a smooth, rounded line on the internal surface of the ala. 19. Ilium The final parts of the ala we ll cover are the superior and inferior iliac spines. The superior and inferior iliac spines are bony projections from the anterior and posterior portions of the ala that provide an attachment point for many of the pelvic muscles. 20. Pubis The second part of the os coxae is the pubis. The pubis makes up approximately 20% of the acetabulum and can be separated into 2 parts: the superior pubic ramus and the inferior pubic ramus. The inferior pubic ramus extends inferolaterally from the medial portion of the superior pubic ramus and connects to the ischium. 21. Pubis The medial portion of each superior pubic ramus is sometimes referred to as the body of the pubis. It is located medially in the inferior pelvis and unites with the contralateral body to form the symphysis pubis. The symphysis pubis is the inferior articulation between the right hemipelvis and the left hemipelvis. The superior pubic ramus then extends superolaterally before joining the ilium and the ischium. 22. Pubis Along the superior border of the superior pubic ramus is a bony ridge known as the pectineal line. The pectineal line, the arcuate line and the sacral prominence form the pelvic brim. The pelvic brim is an obliquely oriented irregular ovoid landmark used to divide the greater and lesser pelvises. The greater pelvis consists of the area above the pelvic brim; it s also known as the false pelvis because it s sometimes considered part of the abdominal cavity. The area below the pelvic brim is called the lesser, or true, pelvis. 23. Ischium Let s move to the next part of the os coxae the ischium. The ischium is located below the ilium and posterolateral to the pubis. Each bilaterally located ischium can be divided into 3 parts: the body, the superior ischial ramus and the inferior ischial ramus. The most superior

6 portion of the ischium, the body, constitutes approximately 40% of the acetabulum. Extending posteriorly from the body is a bony prominence called the ischial spine, which provides an attachment point for multiple pelvic muscles. Located superior and inferior to the ischial spine are bony recesses called the greater and lesser sciatic notches. 24. Ischium Continuing inferiorly and posteriorly from the body of the ischium is the superior ischial ramus. The posterior portion of the superior ischial ramus increases in size and is called the ischial tuberosity. The paired ischial tuberosities are commonly known as the sitting bones, as they bear the weight of the body when a person sits. Extending superiorly and anteriorly from the superior ischial ramus is the inferior ischial ramus. The inferior ischial ramus joins the inferior pubic ramus forming an opening called the obturator foramen. Multiple muscles, vessels and nerves extend through this foramen into the lower extremity. 25. Acetabulum The final bony structure of the pelvis we ll discuss is the acetabulum. The acetabulum is a rounded indentation that receives the femoral head. As you ll recall, each acetabulum is made up of portions of the ilium, pubis and ischium. Surrounding the acetabulum is an irregular prominent ridge that serves for the attachment of the acetabular labrum, a rim of cartilage and connective tissue that is discussed in more detail in the module on the extremities. 26. Knowledge Check 27. Knowledge Check 28. Knowledge Check 29. Pelvic Muscles Next we ll look at the muscles of the pelvis. A number of these are extensions of the abdominal muscles, including the psoas muscles, the rectus abdominis muscles, the internal obliques and the external obliques and the transversus abdominis muscles. 30. Psoas Muscles The psoas muscles are long muscles located on either side of the lumbar spine. Each psoas muscle is generally divided into deep and superficial portions. Each deep portion originates from the transverse processes of the 5 lumbar vertebrae, while each superficial portion originates from the lateral borders of the twelfth thoracic and first through fourth lumbar vertebrae, as well as the intervertebral discs. 31. Psoas Muscles Each psoas muscle joins the ipsilateral iliacus muscle to form the iliopsoas muscle. The iliopsoas muscle then inserts into the lesser trochanter of the femur. The psoas muscles are responsible

7 for lateral flexion of the lumbar spine. In combination with the iliacus muscles, they also play a part in the movement of the hip joint. 32. Rectus Abdominis Muscles The paired rectus abdominis muscles are the most superficial of the abdominal muscles and make up the central portion of the anterior abdominal wall. These muscles are divided vertically by a tendinous sheath called the linea alba, which is Latin for white line. The white collagenous linea alba extends from the xyphoid process to the pubic symphysis. Three, or in some cases 4, other sheaths, called the tendinous intersections, run horizontally. These intersections form the 6-pack or 8-pack appearance of the abdomen seen in very fit individuals. The rectus abdominis muscle originates from the pubic crest and pubis symphysis to the fifth through seventh ribs. It plays roles in flexing the lumbar spine and drawing the ribs toward the pelvis, as well as in forceful expiration. 33. External Oblique Muscles The paired external oblique muscles are found bilaterally deep to the rectus abdominis muscles and make up a portion of the anterolateral abdominal wall. Each external oblique muscle arises from the outer-inferior borders of the fifth through twelfth ribs. The muscle runs anteroinferiorly toward midline before attaching to the anterior iliac crests and abdominal aponeurosis, a thin tendinous-like sheath connecting the muscle to the linea alba. In addition to compressing the abdomen, the external oblique muscles are responsible for flexion of the lumbar spine and lateral flexion of the torso. 34. Internal Oblique Muscles The paired internal oblique muscles are found bilaterally, deep to the external oblique muscles. Like the external obliques, they make up a portion of the anterolateral abdominal wall. Each internal oblique muscle arises from the anterior iliac crest, inguinal ligament and thoracolumbar fascia. The muscle extends anterosuperiorly toward midline before attaching to the costal cartilages of the eighth through twelfth ribs and to the abdominal aponeurosis, which connects the muscle to the linea alba. The internal oblique muscles are responsible for anterior flexion, lateral flexion and rotation of the lumbar spine, as well as abdominal compression. 35. Transversus Abdominis Muscles The last abdominal muscles we ll cover are the paired transversus abdominis muscles, which make up a portion of the anterolateral abdominal wall. Each transversus abdominis arises from the inguinal ligament, the iliac crest and the cartilage of the seventh through twelfth ribs. The muscle extends anteriorly before inserting into the abdominal aponeurosis, which connects the muscle to the linea alba. The transversus abdominis muscles are responsible for compressing the abdominal wall and aiding forceful respiration. 36. Hip Muscles Next, we ll look at 3 major hip muscles that are located in the pelvis: the gluteus maximus, the gluteus medius and the gluteus minimus. The gluteal muscles are located posteriorly and make up the buttocks.

8 37. Gluteus Maximus Muscles The paired gluteus maximus muscles are the largest and most superficial of the gluteal muscles. Each muscle arises from the medial border of the upper iliac crest and the inferior and posterior portion of the sacrum and the coccyx. Extending laterally and inferiorly, the muscle inserts into the iliotibial band and the greater trochanter of the femur. The gluteus maximus muscle is primarily responsible for holding the pelvis and torso onto the femoral head. It also straightens the thigh into a parallel line with the body. 38. Gluteus Medius and Gluteus Minimus Muscles Each of the paired gluteus medius muscles is located deep to each gluteus maximus muscle. In turn, the paired gluteus minimus muscles are found deep to each gluteus medius muscle. Both of these muscle groups originate from the upper outer ilium and insert into the greater trochanter of the femur. When the leg is straightened, these muscles work together to abduct the leg away from midline and externally rotate the hip. With the hip flexed, these muscles internally rotate the hip. 39. Pelvic Floor Muscles Next, we ll focus on the 2 major muscles of the pelvic floor, which also is known as the pelvic diaphragm. The levator ani and the coccygeus muscles support the organs of the pelvis, including the bladder, the intestines and the male and female reproductive organs. They also ensure the proper function of the urinary and anal sphincters. The paired levator ani muscles make up the majority of the pelvic floor. Each muscle attaches anteriorly from the posterior border of the superior ramus of the pubis and posteriorly from the ischial spine. Laterally, each muscle attaches to the obturator fascia, which covers the obturator internus and its attachment points. Each levator ani inserts into the coccyx, the margins of the anus, the side of the rectum and the perineum. 40. Pelvic Floor Muscles The coccygeus muscles also are located bilaterally. Each coccygeus muscle originates from the ischial spine and the sacrospinatus ligament and inserts into the inferior sacrum and superior coccyx. Together with the levator ani muscles, they make up the pelvic floor and support the pelvic organs. 41. Pelvic Floor Ligaments Sometimes, in women, the ligaments supporting the muscles of the pelvic floor weaken. As a result, the pelvic organs also begin to slip. The collapse of the pelvic organs is called prolapse, from Latin meaning to fall out. One of the more common types of prolapse is uterine prolapse, in which the uterus protrudes into the vagina. Although uterine prolapse is associated with older age, the prevalence goes up in women who have had children, especially women who have had multiple or difficult births. 42. Pelvic Cavity Muscles The other muscles of the pelvic cavity include the piriformis muscles, the obturator internus muscles, the obturator externus muscles, the iliacus muscles and the iliopsoas muscles.

9 43. Piriformis Muscles The piriformis muscles originate bilaterally from the anterior surfaces of the sacrum and extend laterally before inserting into the greater trochanters. They are responsible for laterally rotating the thigh and also abducting the thigh away from midline if the hip is flexed. 44. Obturator Internus Muscles The obturator internus muscles originate bilaterally from the obturator membranes and the posterior rims of the obturator foramina. The muscles travel through the lesser sciatic foramina before inserting into the greater trochanters. Like the piriformis, they help to laterally rotate the thigh and abduct the thigh away from midline if the hip is flexed. The obturator internus muscles also help stabilize the hip joint. 45. Obturator Externus Muscles The obturator externus muscles originate bilaterally from the obturator membranes and the anterior rim of the obturator foramina. The muscles travel through the lesser sciatic foramina before inserting into the medial borders of the greater trochanters. They also are responsible for laterally rotating the thigh and adducting the thigh toward the midline. 46. Iliacus and Iliopsoas Muscles Scroll through this animation as we discuss the iliacus and Iliopsoas muscles. The paired iliacus muscles originate from the iliac fossae. Each iliacus muscle extends inferiorly, joining the psoas muscle to form the iliopsoas muscle, which then inserts into the lesser trochanter. The iliacus and psoas muscles can be recognized as 2 separate muscles in the upper pelvis, but by time they reach the inferior pelvis, it s difficult to differentiate between them. Each iliopsoas muscle is responsible for flexing the thigh and the torso. 47. Obturator Test Now that you understand the location and function of the pelvic muscles, let s look at how these muscles relate to some of the maneuvers performed during a physical exam that can suggest intra-abdominal pathology such as appendicitis. The first of these maneuvers is the obturator test. If the appendix is inflamed and adjacent to the obturator muscle, then flexion of the muscle will be painful. To perform this test, the patient lies supine with both the hip and knee flexed at 90-degree angles. The examiner then moves the patient s ankle laterally and medially while the knee remains stationary. This motion flexes the obturator internus muscle and produces pain if the appendix is inflamed and irritating the muscle. 48. Psoas Test The psoas test is another common test for appendicitis. Like the obturator test, the psoas test indicates muscle irritation, in this case of the psoas muscle. For this test, the patient lies supine and lifts the right leg while the clinician applies resistance. It also can be performed by having the patient lie on the left side while the clinician moves the right leg behind the patient. Pain in the right lower quadrant during either of these tests in the appropriate clinical setting is a positive sign and suggests appendicitis.

10 49. Knowledge Check 50. Knowledge Check 51. Knowledge Check 52. Pelvic Cavity Viscera Our next topic is the pelvic viscera, or organs, that are found in both men and women. Digestive system organs located in the pelvis are portions of the small intestine and the large intestine. From the lymphatic system are multiple lymph nodes. Excretory system organs include the urinary bladder, portions of the ureters and the urethra. We ll discuss additional viscera specific to each sex later in the module. 53. Small Intestine Although much of the small intestine is found in the abdominal cavity, we ll specifically cover 2 portions in this module: the terminal ileum and the ileocecal valve. The terminal ileum is the final and most distal portion of the small intestine. It attaches to the cecum, which is the first portion of the large intestine. In gastrointestinal radiology, the terminal ileum is important because it tends to be the site of small intestine pathology. The ileocecal valve is located at the junction of the ileum of the small intestine and the cecum of the large intestine. This valve blocks the reflux of colonic contents back into the small intestine. Symmetric accumulation of fat throughout the ileocecal valve is a commonly seen anatomic variant called lipomatosis of the ileocecal valve and should not be confused with a lipoma, a benign tumor comprised of fat. 54. Ileum The ileum is also the site of the most common developmental malformation of the gastrointestinal tract a Meckel diverticulum. This diverticulum is typically found in the distal 2 feet of ileum and is a remnant of the omphalomesenteric duct, a tubular connection of the yolk sac and small intestine in the embryo. Although it is typically asymptomatic, a Meckel diverticulum can produce symptoms that mimic appendicitis if it becomes inflamed. The diverticulum contains gastric mucosa that secretes acid, producing ulcers like those seen in the stomach or duodenum. 55. Large Intestine The large intestine, or colon, is the final portion of the gastrointestinal tract located in the pelvis. The large intestine absorbs the water from the remaining indigestible material and passes the material from the body. The colon can be divided into 6 segments: the cecum, the ascending colon, the transverse colon, the descending colon, the sigmoid colon and the rectum. However, we ll only cover the cecum, sigmoid colon and rectum in this module. 56. Cecum The cecum is a short segment pouch that marks the beginning of the large intestine. It receives the ileocecal valve of the ileum along its medial border. Typically arising from the inferior medial border of the cecum is the vermiform appendix.

11 57. Vermiform Appendix The vermiform appendix is a long tube-like structure normally found in the right lower quadrant of the abdomen. It is aptly named since vermiform is Latin for worm-like. The direction the appendix travels from the inferior medial border of the cecum varies greatly from patient to patient, and the location of the structure can be abdominal, retrocecal, pelvic or deep pelvic. An abdominal appendix extends superomedially and terminates above the iliac crests. A retrocecal appendix stretches superiorly, posterior to the cecum. A pelvic appendix extends inferiorly, without crossing the iliac vessels. A deep pelvic appendix travels inferomedially and terminates after crossing the iliac vessels. 58. Vermiform Appendix There are 3 views as to the function of the appendix. The first of these options suggests that the appendix is a vestigial structure. The second option is that the appendix is part of the lymphatic system, housing many disease-fighting cells. The third option suggests that the appendix is a reservoir for normal intestinal flora, or bacteria. The colon contains many good bacteria that are necessary to maintain intestinal balance. Some illnesses reduce the number of good bacteria, as does taking antibiotics. When there are a limited number of good bacteria, bad bacteria can proliferate and take over the colon. If this happens, the vermiform appendix holds enough of the good bacteria that can replicate and return balance to the large intestine. 59. Ascending Colon The ascending colon is slightly smaller in diameter than the cecum. It extends superiorly from the cecum to the inferior margin of the liver where it makes a sharp left, or medial, turn. This turn is called the right colic, or more commonly the hepatic, flexure. The colon continues horizontally from this flexure, extending to the left side of the body. 60. Transverse Colon The horizontal colonic segment is called the transverse colon. The transverse colon is the most mobile segment of the large intestine and tends to bow downward while making its way to a point inferior to the spleen. Although generally located in the abdominal cavity, the transverse colon sometimes bows so far inferiorly that portions of it are in the pelvic cavity. 61. Transverse Colon At this point, the transverse colon makes another sharp turn, this time inferiorly. This turn is called the left colic, or more commonly the splenic, flexure. 62. Descending Colon From the splenic flexure, the colon then extends inferiorly to approximately the left iliac crest area of the pelvis, forming the descending colon. From the area of the left iliac crest, the colon continues medially and inferiorly, creating the sigmoid colon. 63. Sigmoid Colon From the left iliac crest, the sigmoid colon is slightly S-shaped as it travels medially before attaching to the rectum along the midline of the pelvis. Commonly, there is redundancy of the sigmoid colon, sometimes with loops extending well into the abdomen. This redundancy can

12 make it impossible for an endoscope to be passed through the sigmoid colon, in which case the rest of the colon can be visualized with CT colonoscopy or a fluoroscopic barium enema. 64. Rectum The rectum is the final portion of the large intestine. Its name comes from rectum intestinum, which is Latin for straight intestine. this straight segment of colon is located posteriorly along the midline of the pelvis. The distal rectum converges to form the anal canal, distal to which is the anus. The anus is the sphincter that controls excretion of solid and semisolid fecal matter from the body. Located lateral to the anal canal are fat-filled spaces called the ischiorectal fossae. 65. Knowledge Check 66. Knowledge Check 67. Excretory System Viscera Next, we ll discuss the viscera of the excretory system that are located in the pelvis. In the pelvis, the excretory system is made up of 3 primary structures: the ureters, the urinary bladder and the urethra. These structures are responsible for storing and excreting liquid waste from the body. 68. Ureters Scroll through this animation as we discuss the ureters. Note the location of the ureters as they pass from the abdomen into the pelvis. The ureters are tubular structures made up of smooth muscle that transport urine from the kidneys to the urinary bladder. Each ureter exits the kidney at the hilum and extends inferiorly to the approximate level of the pelvic brim. At this level, the ureters extend first posteroinferiorly and then anteromedially to the urinary bladder. They enter the posterior border of the bladder obliquely and extend submucosally before emptying into the bladder. Muscular attachments help hold the ureter in its proper place. The muscular attachment and location of the ureter create a valve-like structure that prevents urine from flowing retrograde back toward the kidney, an abnormal condition known as vesicoureteral reflux. 69. Urinary Bladder The urinary bladder is a hollow muscular organ that is pyramid shaped when decompressed. It distends to store urine until the waste is excreted from the body. The base of the urinary bladder is located posteriorly, while the apex of the bladder is located anteriorly. The bladder can remain attached to the anterior abdominal wall, more specifically the umbilicus, by the urachus. 70. Urachus The urachus is a vestigial remnant of the allantois, which is a canal responsible for draining the liquid waste of the fetus via the umbilical cord. In some people, this canal never fully involutes, leading to 4 possible pathological conditions: urachal cyst, urachal fistula, urachal diverticulum and urachal sinus.

13 71. Urachal Pathologies The urachal cyst is a condition in which there is no communication between the umbilicus and bladder, but a portion of the canal is still open. In an urachal fistula, the canal is still patent and urine is free to leak from the umbilicus. An urachal diverticulum is an outpouching of the wall of the urinary bladder at the site of the urachus. Finally, an urachal sinus is a pouch that opens into the umbilicus. 72. Dome of the Bladder The last part of the bladder we ll cover is the dome. The dome of the bladder is located superiorly and is the weakest portion of the bladder wall. This fact is important in cases of bladder rupture from traumatic injury because urine extravasates into different locations based on the site of bladder injury. Types of bladder rupture include intraperitoneal, extraperitoneal and a combination of the two. An intraperitoneal rupture is a tear of the bladder dome in which fluid extravasates into the peritoneal cavity. With an extraperitoneal rupture, fluid leaks into the perivesicular space and possibly extends into the thigh, perineum or scrotum. Just as the name implies, a combination rupture extravasates into both the intraperitoneal and extraperitoneal areas. 73. Urethra You ll remember that urine enters the bladder posterolaterally from the ureters. It exits the bladder via the urethra. An important area of the bladder is a triangular-shaped, smooth muscular area located between the attachment points of the ureters and the urethra. This area is called the trigone of the urinary bladder. As the bladder fills and expands, the trigone sends a signal to the brain that it is time to void. 74. Urethra The urethra is a single tubular structure that exits the urinary bladder and extends to the genital organs, exiting the body through the penis in men and anterior to the vaginal opening in women. At this point, we ll focus on the differences in the male and female pelvises. 75. Male Urethra In men, the urethra measures about 20 cm and can be divided into 4 segments: the preprostatic urethra, the prostatic urethra, the membranous urethra and the spongy urethra. The preprostatic urethra extends from the bladder to the prostate. The portion of the urethra passing through the prostate gland is called the prostatic urethra. The urethra then becomes narrow and extends through the urogenital diaphragm, a portion of the urethra called the membranous urethra. The final part of the urethra extends through the corpus spongiosum of the penis and is called the spongy urethra. Some authors further divide the spongy urethra into the bulbous urethra, which is proximal, and the pendulous urethra, which is distal. Before the urethra exits the penis, there is a small bulbous dilatation named the navicular fossa. When performing a fluoroscopic retrograde urethrogram, the navicular fossa is the site where a catheter balloon may be inflated. Next, we ll move to the male reproductive organs.

14 76. Male Reproductive Organs Multiple structures make up the male genitalia, including the penis, the testes, the epididymides, the vasa deferentia, the ejaculatory ducts, the spermatic cord, the seminal vesicles, the bulbourethral glands and the prostate. Together, these structures produce hormones, the male reproductive cells called sperm and a delivery system to introduce the sperm to the egg for fertilization. 77. Penis The penis is an external male sex organ. Three columns of tissue extend along the length of the penis: 2 corpora cavernosa and 1 corpus spongiosum. The corpora cavernosa are located next to each other along the dorsal, or upper, border of the penis, while the corpus spongiosum is located between each corpus cavernosa along the ventral border, or underside, of the penis. The urethra travels through the corpus spongiosum and exits the body at an opening in the distal penis called the meatus. 78. Scrotum The scrotum hangs from the base of the penis. It is a dual-chambered pouch that contains the external male reproductive organs, including the paired testes and epididymides. The scrotum also holds portions of the paired spermatic cords, which contain the vasa deferentia and multiple vessels. The terms testes and testicles are often used interchangeably, although some authors consider testicles to include the testes and the surrounding structures such as the epididymides and vasa deferentia. Because excess heat can affect the motility, production and movement of sperm, the scrotum functions to keep these organs away from increased body heat. 79. Testes and Epididymides The testes produce sperm and hormones, specifically testosterone. The paired epididymides are located on the posterior surface of each testis. Each epididymis is made up of a coiled tube and connects each testis to the ipsilateral vas deferens. Sperm initially lack motility. During the 2 to 3 months that the sperm pass through the epididymis, the sperm mature and become capable of movement. 80. Vasa Deferentia, Ejaculatory Ducts and Spermatic Cord The vasa deferentia are paired tubular structures that extend from each epididymis superiorly, passing through the prostate and eventually emptying into the urethra via the ejaculatory ducts in the prostatic urethra. Each vas deferens is located within the ipsilateral spermatic cord. Arteries, nerves and lymph vessels also travel into and out of the scrotum through the spermatic cord. 81. Prostate Gland and Seminal Vesicles The prostate gland is located inferior to the bladder and surrounds the urethra. It is responsible for secreting a milky white alkaline substance that makes up about 25-30% of the volume of semen. Located posterior to the prostate gland are the paired seminal vesicles. The seminal vesicles also secrete an alkaline substance that makes up about 65-75% of the volume of semen. These secretions provide fructose, the main energy source for the sperm, and neutralize the normally acidic ph of the vagina.

15 82. Ejaculation During ejaculation, peristalsis moves sperm up each vas deferens. Sperm from the vas deferens converge with fluid from the seminal vesicle into the ejaculatory duct. The paired ejaculatory ducts empty onto an elevation of the prostatic urethra called the verumontanum. Prostatic fluid also empties into the prostatic urethra. The semen is then ejected from the urethra as a result of rhythmic contractions produced by the bulbospongiosus muscle. 83. Bulbourethral Glands The last male pelvic structures we ll mention are the bulbourethral glands. These glands, also called Cowper glands, are located inferior to the prostate and lateral to the membranous urethra. They secrete a clear viscous fluid known as pre-ejaculate. Pre-ejaculate lubricates the urethra to facilitate sperm movement and helps to neutralize any acidic urine remaining in the urethra. 84. Knowledge Check 85. Knowledge Check 86. Knowledge Check 87. Female Reproductive Organs Now let s discuss the female-specific anatomy of the pelvis. In women, the urethra is only 4 to 5 cm long. It extends inferiorly and anteriorly from the inferior portion of the bladder and exits the body between the clitoris and the vaginal opening, or introitus. The difference in length between the male and female urethras is the reason women are more prone to urinary tract infections than men. In men, bacteria must travel 20 cm before causing an infection, whereas in women bacteria travel a much shorter distance. Next, we ll move to the female reproductive organs. 88. Uterus The uterus, commonly known as the womb, is a major internal female reproductive organ located posterior to the urinary bladder. The uterus comprises a body and a cervix. The body makes up the majority of the uterus and is where the attachment and growth of a fertilized egg, or gestation, takes place. The fundus is the top portion of the uterus, opposite the cervix. The fundus is flanked on either side by openings for the uterine or fallopian tubes. 89. Cervix A narrowed segment of the uterus, the cervix communicates with the vagina via a small opening that allows sperm to enter the body of the uterus and menstrual fluid to exit the uterus. This small opening can be further broken down into 2 parts: the internal os and the external os. The internal os is the opening of the cervix into the body of the uterus, and the external os is the opening of the cervix into the vagina. 90. Endometrium, Myometrium and Perimetrium The central cavity of the uterus is surrounded by a wall consisting of 3 layers: the endometrium, the myometrium and the perimetrium. The innermost layer, or endometrium, contains 2 parts:

16 the basal endometrium and the functional endometrium. The basal endometrium is the base layer that gives rise to the functional endometrium. The functional endometrium is shed and reabsorbed monthly in women of reproductive age if no fertilization occurs, causing menstrual bleeding. The middle layer, or myometrium, is primarily composed of smooth muscle. Loose connective tissue called the perimetrium surrounds the myometrium. 91. Uterine Tubes You ll recall from an earlier discussion that each side of the uterine fundus contains openings. These openings are for the uterine tubes, commonly known as the fallopian tubes. The uterine tubes are paired cilia-lined ducts that extend between the uterus and each ovary. They transport eggs from the ovary to the body of the uterus. 92. Ovaries Like the testes in men, the ovaries are paired structures that produce both hormones and reproductive cells. The female reproductive cell is known as the egg, or ovum. The egg is contained within a follicle, where it matures until it is released during ovulation. Sometimes a follicle doesn t release an egg and it continues to grow into a cyst. Alternatively, after releasing an egg, at times the follicle does not reabsorb and also can develop into a cyst. 93. Vagina The vagina is an elastic muscular tube that leads from the outside of the body to the cervix. Recall that the external os of the cervix extends into the vagina. The deep recesses that surround this extension are called the fornices of the vagina. 94. Bartholin Glands Bartholin glands are structures analogous to the male bulbourethral glands. Found bilaterally, posterior to the vaginal opening, these glands secrete a small amount of mucus to lubricate the vaginal opening. If the duct becomes obstructed, a Bartholin cyst can develop, growing up to about the size of a golf ball. 95. Skene Glands Skene glands are bilateral structures that are analogous to the male prostate and are found along the anterior vaginal wall, near the urethra. They secrete a fluid during female ejaculation that is similar to the male ejaculate. Highly variable in anatomy, the Skene glands may be absent in some women. 96. Labia Located on either side of the vaginal opening are 2 separate pairs of skin folds called the labia, which is Latin for lips. The labia are further separated into the labia majora and labia minora. The larger labia majora are the outer pair of folds, and the smaller labia minora are located deep to the labia majora. The clitoris is located where the labia minora meet superiorly. 97. Clitoris The clitoris is reported to be the most sensitive erogenous zone and is analogous to the male penis. It is partially covered by a small fold of skin called the clitoral hood. The exact function of the clitoris other than female sexual pleasure is not certain. It is widely thought that the clitoris has more sensory nerve endings than any other part of the body.

17 98. Ligaments Multiple ligaments are responsible for holding the uterus in place and include the broad ligaments and the paired uterosacral, cardinal and pubocervical ligaments. Each broad ligament is a large fold of peritoneum that extends from the lateral borders of the uterus to the pelvic floor and walls. It contains the fallopian tubes and multiple vessels. 99. Ligaments The uterosacral ligaments arise from the posterior border of the cervix and attach to the anterior border of the sacrum. The cardinal ligaments, also known as the lateral cervical ligaments, originate from the lateral borders of the cervix and attach to the ischial spines of the bony pelvis. The pubocervical ligaments also arise from the lateral borders of the cervix, but attach to the pubic symphysis Pelvic Spaces The complex structure of the female pelvis contains several spaces among the many ligaments and structures. Some of the important ones include the rectouterine pouch, vesicouterine pouch and retropubic space. The rectouterine pouch is a small peritoneal depression located between the uterus and the rectum. The vesicouterine pouch is a small peritoneal recess located superiorly between the bladder and the uterus. The retropubic space is a small recess anterior to the urinary bladder between the bladder and the pubic symphysis Adnexa Another important space contained in the female pelvis is the adnexa. The term adnexa is widely used when talking about the female pelvis, especially with respect to pelvic imaging. In the pelvis, when we say adnexa, we are more specifically referring to the adnexa uteri, or uterine appendages, which include the ovaries, fallopian tubes and the ligaments of the uterus Knowledge Check 103. Knowledge Check 104. Pelvic Blood Supply Our next topic is the arteries and veins of the pelvis. The arterial blood supply of the pelvis begins with the paired common iliac arteries. The common iliac arteries arise from the descending aorta at the approximate level of the fourth lumbar vertebral body. Extending inferolaterally, each common iliac artery bifurcates into an internal and external iliac artery Arterial System The internal iliac artery travels internally and supplies the majority of the pelvic viscera with oxygenated blood. The exceptions are the testes and ovaries, which receive blood from either the testicular or ovarian arteries. The testicular or ovarian arteries originate from the descending aorta at a level just below the renal arteries in the abdominal cavity. The internal iliac artery also gives rise to the gluteal arteries, which supply the gluteal muscles. Each external iliac artery courses anteriorly and inferiorly to the approximate level of the femoral head, where the vessel continues on as the common femoral artery and supplies blood to the lower extremity.

18 106. Venous System The venous system of the pelvis consists of veins with names that correspond to the arteries. The femoral veins return deoxygenated blood from the lower extremity, and at the approximate level of the femoral head, continue superiorly and posteriorly as the external iliac veins. The gluteal veins receive venous blood from the gluteal muscles and empty into the internal iliac veins, which return blood from the pelvic viscera, again with the exception of the testes and ovaries. Typically, the right testicular or ovarian vein empties directly into the inferior vena cava of the abdomen while the left testicular or ovarian vein empties into the left renal vein, also in the abdomen. The external and internal iliac veins then combine to form a common iliac vein, which returns the venous blood to the inferior vena cava Review Scroll through these images to see the arteries and veins of the pelvis we just discussed. As you scroll through the animation, watch the localizer images on the right-hand side. These views will help you recognize the location of the structures Pelvic Lymph Nodes The final structures of the pelvis we ll discuss are the pelvic lymph nodes. The 3 primary groups of pelvic lymph nodes are the external iliac, internal iliac and presacral nodes. The external iliac nodes are clustered around the external iliac arteries and drain lymph from the lower extremity, superior bladder and the superior part of the uterus in women. The internal iliac nodes are clustered around the internal iliac arteries and drain lymph from all the pelvic viscera, excluding the ovaries, testes and superior portion of the rectum. Presacral nodes are found anterior to the sacrum and drain lymph from the prostate, the rectum, the anal canal and in women, the cervix, the uterus and the superior vagina Conclusion This concludes Module 8 of Sectional Anatomy Essentials The Pelvis. You should now be able to: Describe the 3 bones that form the pelvic girdle. Name and locate the contents of the lower abdominal cavity. Locate and describe the function of the pelvic muscles. Identify and describe the location and function of the pelvic organs. Track the flow of urine within the pelvic region. Identify and describe the location and function of the components of the male reproductive system. Identify and describe the location and function of the components of the female reproductive system. Follow the course of arterial and venous blood flow within the pelvis Resources 111. Development Team 112. Acknowledgements 113. Module Completion