. Diseases of the rectum and anus: designed for students and practitioners of medicine. s surrounding the anus, whichblend internally with the submucosa and externally with theintegument. By contracting, it gathers the skin about the anusinto folds. External Sphincter.—This muscle is voluntary, and is situ-ated immediately beneath the integument at the anal is about three inches ( centimeters) in length, half aninch ( centimeters) broad, and is quite thin. It arises fromthe tip of the coccyx, and, after surrounding the anus in theform of an ellipse, is inserted into the centr
. Diseases of the rectum and anus: designed for students and practitioners of medicine. s surrounding the anus, whichblend internally with the submucosa and externally with theintegument. By contracting, it gathers the skin about the anusinto folds. External Sphincter.—This muscle is voluntary, and is situ-ated immediately beneath the integument at the anal is about three inches ( centimeters) in length, half aninch ( centimeters) broad, and is quite thin. It arises fromthe tip of the coccyx, and, after surrounding the anus in theform of an ellipse, is inserted into the central tendon of theperineum. The action of this muscle is to close the anal orificeand assist in the expulsion of the feces, acting in conjunctionwith the abdominal muscles and levator ani. Its nerve-supplyis derived from the fourth sacral and the inferior hemorrhoidalof the internal pudic, and the center controlHng it is situatedin the lumbar enlargement of the cord. Transversus Perinei.—This muscle arises by a narrow ten-don on the anterior surface of the tuber ischii, and passes. PLATE ni.—LEVATORES ANI A8 SEEN FROM ABOVE, SHOWING HOW THEY PASS AROUND THE RECTUM. A, Bladder. B^ Prostate. C, Reotum. B D, Levatores am. ANATOMY AND PHYSIOLOGY 17 forward and inward to be inserted into the central tendon ofthe perineum at the junction with the anterior insertion of theexternal sphincter, and, in the female, with the posterior at-tachment of the sphincter vaginae. According to Cruveilhier,it aids in defecation by pressing the anterior and posteriorwalls of the bowel together, in conjunction with the externalsphincter. Internal Sphincter. — This is a fiat, involuntary muscularband formed by a collection of the fibers of the circular coat,lying immediately above the external sphincter. It is fromthree-fourths of an inch ( centimeters) to an inch () in breadth, and one-sixth of an inch ( milli-meters) in thickness. Its fibers are somewhat finer and palerthan
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanusdis, bookyear1910
