clinically oriented anatomy (9/e): part 2

6 Pelvis and Perineum<br /> <br /> INTRODUCTION TO PELVIS AND PERINEUM<br /> PELVIC GIRDLE<br /> Bones and Features of Pelvic Girdle<br /> TABLE 6.1. Comparison of Male and Female Bony Pelves<br /> Orientation of Pelvic Girdle<br /> Pelvic Girdle Sexual Differences<br /> Joints and Ligaments of Pelvic Girdle<br /> CLINICAL BOX: Pelvic Girdle<br /> PELVIC CAVITY<br /> Walls and Floor of Pelvic Cavity<br /> TABLE 6.2. Muscles of Pelvic Walls and Floor<br /> Peritoneum and Peritoneal Cavity of Pelvis<br /> TABLE 6.3. Peritoneal Reflections in Pelvis<br /> Pelvic Fascia<br /> CLINICAL BOX: Pelvic Cavity<br /> NEUROVASCULAR STRUCTURES OF PELVIS<br /> Pelvic Arteries<br /> TABLE 6.4. Arteries of Pelvis<br /> Pelvic Veins<br /> Lymph Nodes of Pelvis<br /> Pelvic Nerves<br /> TABLE 6.5. Somatic Nerves of Pelvis<br /> CLINICAL BOX: Neurovascular Structures of Pelvis<br /> 1293<br /> <br /> PELVIC VISCERA<br /> Urinary Organs<br /> Rectum<br /> TABLE 6.6. Parts of Male Urethra<br /> CLINICAL BOX: Urinary Organs and Rectum<br /> Male Internal Genital Organs<br /> CLINICAL BOX: Male Internal Genital Organs<br /> Female Internal Genital Organs<br /> CLINICAL BOX: Female Internal Genital Organs<br /> Lymphatic Drainage of Pelvic Viscera<br /> TABLE 6.7. Lymphatic Drainage of Structures of Pelvis and Perineum<br /> PERINEUM<br /> Fasciae and Pouches of Urogenital Triangle<br /> Features of Anal Triangle<br /> TABLE 6.8. Arteries of Perineum<br /> CLINICAL BOX: Perineum<br /> Male Urogenital Triangle<br /> TABLE 6.9. Muscles of Perineum<br /> CLINICAL BOX: Male Urogenital Triangle<br /> Female Urogenital Triangle<br /> TABLE 6.10. Nerves of Perineum<br /> CLINICAL BOX: Female Urogenital Triangle<br /> SECTIONAL IMAGING OF PELVIS AND PERINEUM<br /> Magnetic Resonance Imaging<br /> <br /> INTRODUCTION<br /> PERINEUM<br /> <br /> TO<br /> <br /> 1294<br /> <br /> PELVIS<br /> <br /> AND<br /> <br /> In common usage, the pelvis (L. basin) is the part of the body’s trunk that is<br /> inferoposterior to the abdomen and is the area of transition between the trunk<br /> and the lower limbs. The pelvic cavity is the inferiormost part of the<br /> abdominopelvic cavity. Anatomically, the pelvis is the part of the body<br /> surrounded by the pelvic girdle (bony pelvis), part of the appendicular skeleton<br /> of the lower limb (Fig. 6.1).<br /> <br /> FIGURE 6.1. Pelvis and perineum. A, B. The pelvis (green) is<br /> the space within the pelvic girdle, overlapped externally by the<br /> abdominal and gluteal regions, perineum, and lower back.<br /> Consequently, the pelvis has no external surface area. The<br /> greater pelvis (light green) is pelvic by virtue of its bony<br /> boundaries but is abdominal in terms of its contents. The lesser<br /> pelvis (dark green) provides the bony framework (skeleton) for<br /> the pelvic cavity and deep perineum.<br /> The pelvis is subdivided into greater and lesser pelves. The greater pelvis is<br /> surrounded by the superior pelvic girdle. The greater pelvis is occupied by<br /> inferior abdominal viscera, affording them protection similar to the way the<br /> superior abdominal viscera are protected by the inferior thoracic cage. The lesser<br /> pelvis is surrounded by the inferior pelvic girdle, which provides the skeletal<br /> framework for both the pelvic cavity and the perineum—compartments of the<br /> trunk separated by the musculofascial pelvic diaphragm. Externally, the pelvis is<br /> covered or overlapped by the inferior anterolateral abdominal wall anteriorly, the<br /> gluteal region of the lower limb posterolaterally, and the perineum inferiorly.<br /> <br /> 1295<br /> <br /> The term perineum1 refers both to the area of the surface of the trunk<br /> between the thighs and the buttocks, extending from the coccyx to the pubis, and<br /> to the shallow compartment lying deep (superior) to this area but inferior to the<br /> pelvic diaphragm. The perineum includes the anus and external genitalia: the<br /> penis and scrotum of the male and the vulva of the female.<br /> 1The term perineum has been used in different ways, in different languages, and<br /> <br /> in different circumstances. In its most restricted sense, and in obstetrics, it has<br /> been used to refer to the area superficial to the perineal body, between the vulva<br /> or scrotum and the anus or to the perineal body itself. In an intermediate sense, it<br /> has included only the perineal region, a superficial (surface) area bounded by the<br /> thighs laterally, the mons pubis anteriorly, and the coccyx posteriorly. In its<br /> widest sense, as used in Terminologia Anatomica (the international anatomical<br /> terminology), and in this book, it refers to the region of the body that includes all<br /> structures of the anal and urogenital triangles, superficial and deep, extending as<br /> far superiorly as the inferior fascia of the pelvic diaphragm.<br /> <br /> PELVIC GIRDLE<br /> The pelvic girdle is a basin-shaped ring of bones that connects the vertebral<br /> column to the two femurs. The primary functions of the pelvic girdle are to<br /> bear the weight of the upper body when sitting and standing.<br /> transfer that weight from the axial to the lower appendicular skeleton for<br /> standing and walking.<br /> provide attachment for the powerful muscles of locomotion and posture and<br /> those of the abdominal wall, withstanding the forces generated by their<br /> actions.<br /> Consequently, the pelvic girdle is strong and rigid, especially compared to<br /> the pectoral (shoulder) girdle. Other functions of the pelvic girdle are to<br /> contain and protect the pelvic viscera (inferior parts of the urinary tracts and<br /> the internal reproductive organs) and the inferior abdominal viscera (e.g.,<br /> intestines), while permitting passage of their terminal parts (and, in females,<br /> a full-term fetus) via the perineum.<br /> provide support for the abdominopelvic viscera and gravid (pregnant) uterus.<br /> <br /> 1296<br /> <br /> provide attachment for the erectile bodies of the external genitalia.<br /> provide attachment for the muscles and membranes that assist the functions<br /> listed above by forming the pelvic floor and filling gaps that exist in or<br /> around it.<br /> <br /> Bones and Features of Pelvic Girdle<br /> In mature people, the pelvic girdle is formed by three bones (Fig. 6.2A):<br /> <br /> FIGURE 6.2. Pelvic girdle. A, B. Features of the pelvic girdle<br /> demonstrated anatomically (A) and radiographically (B). The<br /> pelvic girdle is formed by the two hip bones (of the inferior axial<br /> 1297<br /> <br />