Anorectal Fistula and Pelvirectal Abscess
The muscles of the pelvic floor may be thought to assume the anatomical configuration of two cylinders, one within the other. The inner cylinder consists of the lower rectum and anal canal, which contains mucosa and submucosa as well as the circular and the longitudinal muscle layers. In the anal canal the circular muscle layer is very well developed and constitutes the internal sphincter muscle, an involuntary sphincter made up of smooth muscle. The outer cylinder consists of the external sphincter and the puborectalis muscles. At its proximal extremity the outer cylinder fans out in the shape of a funnel since it is continuous with the levator ani muscles that form the pelvic diaphragm. The inner visceral muscle cylinder and the outer somatic cylinder are separated by the intersphincteric space (Fig. 89 – 1).
KeywordsAnal Canal External Sphincter Internal Opening Internal Sphincter Anorectal Fistula
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