A textbook of obstetrics . unt the muscles, ligaments, connective tissue,blood-vessels, lymphatics, and nerves. The Muscles.—The iliopsoas, the obturator internus, and thepyriformis clothe the pelvic walls, modifying the diameters ofthe pelvic cavity and acting as buffers or cushions to protect thechilds body in its passage through the birth-canal. The bulkyiliopsoas muscles diminish the transverse diameter of the pelvicinlet by five centimeters, thus making the oblique diameters of the 26 PREGNANCY, pelvic inlet the longest and insuring ordinarily an oblique positionof the presenting part, bu
A textbook of obstetrics . unt the muscles, ligaments, connective tissue,blood-vessels, lymphatics, and nerves. The Muscles.—The iliopsoas, the obturator internus, and thepyriformis clothe the pelvic walls, modifying the diameters ofthe pelvic cavity and acting as buffers or cushions to protect thechilds body in its passage through the birth-canal. The bulkyiliopsoas muscles diminish the transverse diameter of the pelvicinlet by five centimeters, thus making the oblique diameters of the 26 PREGNANCY, pelvic inlet the longest and insuring ordinarily an oblique positionof the presenting part, but these muscles are subject to compres-sion and to some displacement under pressure in labor, and, ifthe pressure is excessive, the transverse diameter again becomesthe longest ; hence the transverse position of the head in ob-structed labors. The coccygeus, the levator ani, the retractor ani,the sphincter ani, the constrictor vaginae, and the transversusperinei are the muscles of the pelvic floor giving the direction to. Fig. 8.—The pelvis with soft parts, bladder, rectum, uterus, and its appendages havingbeen removed (from a model in the University of Pennsylvania). the lower part of the parturient tract in labor and directing thepresenting part forward, outward, and upward under the pubicarch. The levator ani is by far the most important muscle in thepelvic floor. It is a strong, horseshoe-shaped band of muscle,consisting of two symmetrical halves slung back from the anteriorpelvic wall and surrounding the vagina and rectum. It is thechief factor in pushing the presenting part forward away from the THE ANATOMY OF THE PELVIS. *7 perineum and out through the vulvar orifice. It is thus the chiefconservator of the integrity of the pelvic floor in labor. Its injuryrobs the rectum and posterior vaginal wall of their strongest sup-port, allowing them to drop downward, outward, and forward inthe rectocele, with which the gynecologist has to deal in second-ary operations upon so-
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectobstetrics, bookyear1
