Ischemic pain - Overview of the Pelvic Cavity, Pelvic...

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Overview of the Pelvic Cavity, Pelvic Viscera, Perineum and External genitalia Pelvic Cavity The pelvis may be described in terms of a “Greater” (False) pelvis and a “Lesser” (True) pelvis. The “Lesser” or True pelvis is located between the pelvic inlet and outlet, is surrounded by bones, and contains the pelvic organs. The “Greater” or False pelvis is located superior to the pelvic inlet, is bounded anteriorly by the abdominal wall, and contains some of the abdominal viscera. The pelvic inlet (superior pelvic aperture) is described by a plane that connects the sacral promontory, arcuate line of the ilium, pectineal line of the pubis and the pubic crest. (The arcuate line, the pectineal line and the pubic crest form the linea terminalis.) Its edge is known as the “pelvic brim”. A line connecting the sacral promontory with the superior margin of the pubic symphysis is known as the “conjugate diameter” of the pelvic inlet. The “obstetric conjugate” is the diameter of the pelvic inlet measured from the midpoint of the pubic symphysis to the sacral promontory. It is a fixed diameter. The “diagonal conjugate” is the diameter of the pelvic inlet from the inferior border of the pubic symphysis to the sacral promontory, and is a clinical measurement utilized in obstetrics to estimate cephalopelvic proportion when developing a prognosis for the progression of labor and delivery. The obstetric conjugate is 1.5 – 2.0 cm. shorter than the diagonal conjugate. In a gynecoid pelvis, the biparietal diameter of the infant (9.0 cm) typically passes through the obstetric conjugate. The interspinous diameter (distance between the two ischial spines) is an important mid- pelvic measurement. It serves as a marker for “station” of the baby’s head in obstetrics. The head is described as located above the plane (minus 1-5 station), below the plane (plus 1-5 station) or at the plane (0). When the leading part of the bony skull is located at the plane, the head is described as being “engaged”. The differences in the male and female pelvis are noted in the table below: Structure/Section Female Male pelvic inlet oval and rounded heart- shaped pelvic outlet large small pubic arch and subpubic angle wide narrow iliac wings flared less flared Additionally, there are 4 different types of pelves: android, anthropoid, gynecoid and platypelloid. The gynecoid is the most common type in females occurring in 50% of women. The android is the most common type in males, although 20-30% of females have this type. The pelvic outlet is narrower. The anthropoid is more common in African-American females. The platypelloid is a rare type.
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The pelvic outlet (inferior pelvic aperture) is covered by the pelvic diaphragm composed of the coccygeus and levator ani muscles. The pelvic diaphragm is a funnel shaped muscular floor of the pelvic cavity that provides support for the pelvic organs (viscera). The pelvic diaphragm resists increases in intra-abdominal pressure that occur in
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Ischemic pain - Overview of the Pelvic Cavity, Pelvic...

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